UNIVERSITY OF CALIFORNIA COLLEGE OF AGRICULTURE AGRICULTURAL EXPERIMENT STATION BERKELEY, CALIFORNIA CIRCULAR 318 August, 1930 TERMITES AND TERMITE DAMAGE WITH PRELIMINARY RECOMMENDATIONS FOR PREVENTION AND CONTROL S. F. LIGHT, MERLE RANDALL, and FRANK G. WHITE NYMPH OF THE COMMON - DRY-WOOD TERMITE I. Biological Information Concerning Termites II. Prevention and Eradication by Chemical Treatment III. Prevention by Construction Methods ORGANIZATION OF THE TERMITE INVESTIGATIONS COMMITTEE Officers Chairman, A. A. Brown Vice-Chairman, W. H. Kirkbride Secretary- Treasurer, J. Walter Kelly 215 Market Street, San Francisco, California Board of Directors Chairman, A. A. Brown, Consulting Engineer, Matson Navigation Company, Cali- fornia and Hawaiian Sugar Corporation, Chairman Subcommittee on Finance. Secretary, J. Walter Kelly, Sales Manager, Chas. R. McCormick Lumber Com- pany. R. C. Barton, Outside Plant Engineer, Pacific Telephone and Telegraph Co., Chairman Subcommittee on Pole Lines. W. H. Dore, Associate Chemist, Agricultural Experiment Station. E. O. EssiG, Professor of Entomology. Emanuel Fritz, Associate Professor of Forestry. R. F. Hammatt, Secretary-Manager, California Redwood Association. W. H. Hampton, Research and Development Department, Standard Oil Company of California, Chairman Subcommittee on Historical and Service Records. W. B. Herms, Professor of Parasitology, Head Division of Entomology and Parasitology, College of Agriculture. A. C. Horner, Manager Western Office, National Lumber Manufacturers Asso- ciation, Chairman Subcommittee on Lumber Yards and Producers, Vice-Chair- man Subcommittee on Publicity. W. M. Hoskins, Assistant Professor of Entomology, Assistant Entomologist, Agricultural Experiment Station. C. B. Hutchison, Dean College of Agriculture, Director of Agricultural Experi- ment Station, Director of Giannini Foundation of Agricultural Economics, Chairman Subcommittee on Agriculture Pertaining to Rural Buildings and Structures. W. C. Jacobsen, Director of the Bureau of Plant Quarantine and Pest Control, State of California, Chairman Subcommittee on Legal Advice. W. H. Kirkbride, Engineer of Maintenance of Ways and Structures, Southern Pacific Company, Chairman Subcommittee on Building Departments and Railroad Structures. C. A. Kofoid, Professor of Zoology, Chairman Department of Zoology, Chairman Subcommittee on Biology, Chairman Advisory Council. S. F. Light, Professor of Zoology, Chairman Subcommittee on Publicity, Vice- Chairman Subcommittee on Biology, C. B. Lipman, Dean of the Graduate Division, Professor of Plant Physiology. Walter Putnam, City Superintendent of Building, Pasadena, Chairman Sub- committee on Building Construction Details. Merle Randall, Professor of Chemistry, Chairman Subcommittee on Chemistry. E. C. Van Dyke, Professor of Entomology. O. R. West, Division Engineer, Atchison, Topeka and Santa Fe Railway. F. G. White, Chief Engineer Board of State Harbor Commissioners, Chairman Subcommittee on Engineering and Specifications. J. W. Williams, Chief Engineer Western Pacific Railroad. C. E. Young, Assistant Engineer of Operations, Pacific Gas and Electric Com- pany, Chairman Subcommittee on Protections and Tests. Dr. T. E. Snyder, Senior Entomologist, United States Department of Agriculture at Washington, Dr. Alfred Emerson, Associate Professor of Zoology, University of Chicago, Mr. George M. Hunt, Forest Products Laboratory, U. S. Forest Service, Madison, Wisconsin, and Mr. E. M. Ehrhorn, Consulting Entomologist, Honolulu, T. H., are members of the committee and act in an advisory capacity. Advisory Council Appointed by the President of the University of California: C. A. Kofoid (Chairman), W. H. Dore, E. O. Essig, Emanuel Fritz, W. B. Herms, W. N. Hoskins, S. F. Light, C. B. Lipman, Merle Randall, E. C. Van Dyke. Executive Committee A. A. Brown (Chairman), J. Walter Kelly (Secretary), C. A. Kofoid, A. C. Horner, Merle Randall. Executive Secretary E. E. Bowe, National Lumber Manufacturers Association. TERMITES AND TERMITE DAMAGE WITH PRELIMINARY RECOMMENDATIONS FOR PREVENTION AND CONTROL S. F. LIGHT i MERLE RANDALL 2 and FRANK G. WHITES FOREWORD Termites of various native species are found throughout California ; no district can safely be considered free from their attack. Because of the insidious nature of the infestation, the extent and importance of the damage they cause has long been underestimated. The damage to houses has been increasing in recent years, seemingly because of the rapid building up of the country, with the consequent multiplication of buildings and other structures not so designed or constructed as to prevent the access of termites, giving rise to conditions favorable to their increase and dissemination. The Termite Investigations Committee was formed less than two years ago as a cooperative effort between various industries concerned and the University of California. The personnel of the committee appears on the opposite page. Among the contributors are various railroad and steamship companies, oil companies, lumber associations, power companies, telephone and telegraph companies, sugar refineries, wood-preserving companies, and the Board of State Harbor Commis- sioners of California. The committee has as its ultimate aim the discovery of the most effective methods of prevention and control of the damage done by termites. Circular 314, Termites and Termite Damage, which presented a brief description of the termites, their habits, and the damage they do and certain tentative recommendations for prevention and control, is now out of print, The present circular is a further contribution from the committee, covering the same ground and presenting in a general and non-technical form such additional knowledge as to the local termites and such conclusions as the committee has tentatively arrived at as to the most satisfactory methods for the prevention and control of termite damage. ~ _> XT ^ C. B. Hutchison, Director, California Agricultural Experiment Station. 1 Professor of Zoology, University of California. 2 Professor of Chemistry, University of California. 3 Chief Engineer, Board of State Harbor Commissioners. University of California — Experiment Station Fig. 1. — On opening any termite colony individuals of several different types or castes may be seen. The photograph shows these castes of the large Pacific Coast damp-wood (rotten-wood) termite, Termopsis angusticollis, magnified five times. The most numerous type is smaller and lighter and made up of the young known as nymphs (b, c) and in the subterranean termites of workers (fig. 9a). Most conspicuous are the soldiers (d) with their darker, massive, heavily armored heads and relatively enormous mandibles or pincers. Certain nymphs (b) change into soldiers while others (c) bear wing pads showing that they will give rise to the winged reproductives (a) which swarm from the nest at certain seasons to found new colonies. Circ. 318] Termites and Termite Damage I. BIOLOGICAL INFORMATION CONCERNING TERMITES 4 WHAT ARE TERMITES? Termites are insects. Like other insects they have six legs (fig. Id) and their bodies are made up of segments arranged in three regions, head, thorax, and abdomen. The head bears a pair of antennae, or feelers, and a pair of mandibles and other complicated mouthparts. In some cases a pair of black compound eyes is present (fig. 14a). The thorax is made up of three segments, each of which bears one pair of legs. The wings when present (fig. la) are borne on the first two segments. Most of the individuals of any kind of termite, however, are entirely wingless and either entirely eyeless or possessed of but vestiges of eyes. Termites have a horny outer covering, which is shed or molted at various times during development to allow for increase in size and changes in structure (see fig. 14, p. 20). This covering is much thinner in the termites than in insects living an exposed life. The termites as a group are very ancient. Their nearest relatives are the cockroaches, from which they have probably been distinct for many millions of years. Fossil termites, of the very genus whose species are doing damage all over the United States, have been found in deposits known to be millions of years old. There is every reason to believe that our local termites were here long before man appeared on the scene. Termites are commonly, but erroneously, called 'white ants.' Not all species and kinds of termites are white. The forms of our common, ground-dwelling termite that are commonly seen, are white, but others of the same species have jet-black bodies. Termites are not ants (see page 14), nor, as pointed out above, are all species and forms white. The term 'white ant' therefore should be eliminated ; it leads to serious misconceptions as to identity, habits, and methods of control of the insects properly named termites. Please cooperate to put this name, termite, into general use. Social Instincts Termites are social insects. Just as honey bees live in colonies, have a distinct social life, and have their work divided among a queen, drones, and workers, so do the termites live in colonies, have 4 This section was prepared by S. F. Light, Professor of Zoology, Vice- Chairman Subcommittee on Biology of Termite Investigations Committee. 6 University of California — Experiment Station a social life, and divide their work among specialized castes. In details of their life, such as food habits, nature and location of dwellings, relation of castes, and methods of colony formation, they differ markedly, however, from the honey bees. Not only are termites social, living in colonies, but each colony lives entirely shut off from the outside world and from interconnection with other colonies of termites, even of the same species. The dwelling of the colony consists either of intercommunicating cavities within wood (fig. 16) or of connecting passageways within both the ground and the wood, often interconnecting by dark, earth-like runways or tunnels constructed by the termites (figs. 2 and 20). Termites thus live in darkness, in narrow passageways, where the temperature, the moisture, and probably the oxygen pressure are to some extent under their control. This cryptobiotic habit is of the utmost importance in any consideration of the termites. To its influence through the ages are due most of the characters of the workers and soldiers, their lack of eyes, of wings, of dark color, and of thick body covering (figs. 5 and 9). This habit of termites, of living in separate enclosed colonies, presents certain difficulties in prevention and control, as will appear in a later section, since each colony must be treated separately. Particularly does this habit render extremely improbable any satisfactory natural control by means of other animals or communicable diseases. Food Habits Termites possess more highly developed social habits than any other animals save perhaps the ants and the bees. This development has been made possible by their ability to avail themselves of an extremely abundant and constant food supply in cellulose, the hard part of plants. Termites ordinarily feed on wood ; hence our present concern in them. All castes except the soldiers have mandibles adapted to cutting off little fragments of wood (fig. 3a). There are many difficult points not yet understood about their methods of digesting and using as food a material so resistant as is cellulose to the digestive juices of most other animals, but the fact remains that they will live, grow, and multiply on a diet of pure cellulose, such as purified filter paper. Indeed, their ordinary laboratory diet is filter paper. One of the most interesting results of studies on the food habits of termites was the discovery that in all save the highest family the intestine of the termite swarms with thousands of one-celled animals, or Protozoa, of a very complex type (fig. 35). All our common termites have such Protozoa. Circ. 318] Termites and Termite Damage » 53- C is- » » S3 >d I g. • a* g,^ S £ g I I o ? ^ 89 5" CD J5 a "* s^ a on •— '" M © a, m . £ p h o ^p a 2 s ps a, h» a oq £L p, a h ©j ST oj o a o ^ c+- 2L jo p a as © <^ o jo a c g ^ H B" a- a- 2- a *g CD _ ST p. n O ca 0K3 CD w -^ o a ^ so c a£ ^ CD « O O rt ±?- ca f 5 h a ^ •— — ' CD p a o ■» w ea Pj <1 £• C j£ &• J- 3 3 «> CD H,g ^^5'g g g s a a a - H * a '^■ao c+- Pj CD a ca ■ P ^ a . O ►g a • © C5 o O^ J> CD ; a CD Hs Hs - — CD C 1 & CD O °° Hsq a- _, CD ■< CD ^ a- £ o ^2 cf B CD x CD Ha a. 3 DO 1 CD X H < P CD 05 a cd cr x CD i-i <-i CD a CD o a X a 3 o a a 3. H - H CD - o Hs O CD on' a_ 3" — a X B O — a jq a" a C o CD CO a £ CD Hs Ha P P tj CD a' a- CD rt. o c pj 5 CD ■< M 7 5 6 o Ha P3 CD 00 CD a of a c a H cy !^. CD CD a. a a a. rt- SO w' a Pj X hfe c ►1 P 4 Hs 5 P ca CD 5" w CD SB Efl ? CD 05 CD CD o H o CD oo CD P ca CO CD 1 CD DO B CD Hs CD OQ P x a" Hs P O CD CD r+ Si p' r^ P £ 3- 'D fj . 05 1— l CD a p Hs O o Pj rh CD O ■ CD x O University of California — Experiment Station Fig. 3. — Termites are wood feeders. All castes, save the soldiers, possess wood-cutting instruments in the form of hard, sharp, toothed mandibles, which work against one another in the mid-line of the head. The mandibles shown above (a) are those of a reproductive of the subterranean termite Coptotermes, which is responsible for much of the damage done by termites in the tropics. Strangely enough the wood-eating termites are not able to digest the wood alone, but depend upon thosusands of one-celled animals, Protozoa (h), which swarm in their intestines and take a necessary part in the digestion of the wood, the tiny fragments of which it may be seen they take into their sub- stance and at least partially digest. Circ. 318] Termites and Termite Damage 9 Examination shows that these Protozoa contain in the living sub- stance of their bodies many of the wood fragments chewed off by the termites and experimentation shows that the termites die of starvation if the Protozoa are removed. This can be readily clone by putting them in an atmosphere of oxygen at high pressure, which kills the Protozoa but not the termites. Fig. 4. — Only a brief observation of termites under normal conditions emphasizes the fact that one of the most constant and probably most important features of their social relations is the constant licking of their own bodies and those of the other members of the colony. This grooming habit is of the utmost practical importance since any poisonous substance in the form of a fine dust which is caught on the fine hairs covering the body is passed on from member to member (see pages 40, 41). For example when a single individual was dusted with the violent poison, white arsenic, and placed in a dish 5 inches in diameter with 149 other termites, all were dead within thirty hours, due to the spread of the poison in this manner. Grooming Another very important habit of termites is the constant licking or grooming of their own bodies and the bodies of other members of the colony (fig. 4). This is extremely important in the dissemination of dust poisons through the colony. It has been found, for example, that if one individual is dusted with white arsenic and placed with 149 others in a space of 20 square inches all will be dead in about 30 hours, while others under identical conditions, but without exposure to poison, live indefinitely. Termite Castes Termites have developed a system of division of labor. Each colony consists of various kinds of individuals especially fitted in form and by instinct to carry on diverse activities. These different kinds of individuals are known as castes. There are usually three castes: reproductives, workers, and soldiers (fig. 22). Certain termites have no specially developed workers, but the grub-like young individuals of the other castes, known as nymphs (fig. 5), do the work of the colony. 10 University of California — Experiment Station Fig. 5. — The wood-dwelling termites have no permanent worker caste. The work of the colony is done by the young, known as nymphs, which will later become either soldiers or reproductives. The photograph shows a nymph of Kalotermes minor, the common dry-wood termite. Note its general white and unprotected appearance and the discoloration of the abdominal region due to the intestinal contents. The Reproductive Caste The reproductives (figs, la, 6, 7, 8, 18a, 22&, c, i, 23) are male and female termites which are much more like ordinary insects than are the other castes. They have large, black, compound eyes; somewhat flattened bodies ; and a thick, often dark-colored, body covering. They Fig. 6. — For the brief half-hour or less of the swarming period these winged forms resume the free-living, flying habits of the ancestral termites, being strongly attracted by the light. As soon as they have paired and lost their wings they again revert to the light-fleeing habits characteristic of termites. The photograph shows a swarming individual of the western subterranean termite, Reticulitermes hesperus. emerge as winged forms (alates) from established colonies at a more or less definite time each year (figs, la, 6, and 23). These flying termites are often mistakenly called 'flying ants.' They mate, drop their wings, and each successful pair starts a new colony, of which they are the permanent king and queen (fig. 7). In most termite colonies, the body of the queen becomes enlarged owing to the great develop- Goto. 318] Termites and Termite Damage 11 ment of the ovaries, thus allowing for more rapid egg-laying (fig. 8). Queens of our local termites show less enlargement than those of tropical species, which reach a length of 3 inches or more. Termites, like bees, have the remarkable power of producing supple- mentary reproductives when needed, in some way not understood. These supplementary reproductives are nymphs in various stages whose reproductive development is suddenly speeded up while their Fig. 7. — The winged males and females, which emerge during the autumn, assort in pairs, break off their wings at a preformed joint, and set about the establishment of new colonies of which they are the permanent kings and queens. The photograph shows a royal pair of damp-wood termites, the king (a) to the left and the queen (&) to the right. Fig. 8. — The queen soon begins to lay eggs and as time goes on the ovaries continue to grow, the abdomen becoming elongated and swollen, and the plates which formerly covered it becoming widely separated. The photograph shows such a physogastric queen of a subterranean termite, considerably enlarged. normal development into soldiers or alates is inhibited save for a certain increase in pigmentation. They are, therefore, as a rule darker than other nymphs but much less heavily pigmented and chitinized than are the first-born kings and queens and have, at the most, but rudiments of eyes and wings. The very great importance of this ability of the termites is that it makes a colony potentially immortal and also may allow for increase in colonies independently of the swarming alates by the migration or chance cutting off of small groups. 12 University of California — Experiment Station The Worker Caste The workers (fig. 9a) are by far the most numerous members of a subterranean termite colony, and the ones commonly encountered. They are the palest, usually the smallest, and the weakest in appear- ance, of the adults found in a colony. They are wingless, blind, and usually entirely eyeless, with pale, rounded heads, inconspicuous jaws, and thin body covering. Nevertheless, this is the form which does all the work of the colony, such as gathering food, taking care of and Fig. 9. — In spite of their appearance of weakness the workers (a), as the name suggests, do the work of the colony, and all termite destruction is due to their activities, together with that of the young. Wood-dwelling termites have no workers and the work of their colonies is accomplished by young stages of individuals which will become soldiers or reproductives (see fig. 5). The soldier (b) of this species, Reticulitermes hesperus, the western subter- ranean termite, is also white-bodied but has a pale yellow head. By means of its heavy mandibles and large head it defends the colony against attack from other insects. The worker and soldier are here shown about sixteen times natural size. Circ. 318] Termites and Termite Damage 13 feeding the young, the king and queen, and the soldiers, and building such structures as the tunnels, mounds, nests, and fungus gardens, which the various termite species make. It is the workers, together with the immature individuals called nymphs, that give us our termite problem. The Soldier Caste Wingless, blind, practically eyeless, and sterile, the strange mem- bers of the termite community known as soldiers (figs. Id, 9b, 10) attract the eye by reason of their greatly enlarged, colored, elongated Fig. 10. — The soldiers of the three common economically important termite species of California differ markedly in size. They are shown here each enlarged about four times, (a) The common damp-wood termite, Termopsis angusticollis ; (b) the western subterranean termite, Reticulitermes hesperus ; (c) the common dry-wood termite, Kalotermes minor. heads, usually more or less rectangular in shape, which are covered with a hard, thick armor and armed with greatly enlarged, elongated, and often grotesquely toothed jaws used as weapons of defense. 14 University of California — Experiment Station These soldiers, like those of man, seem to function chiefly, if not entirely, in cases of emergency, as when the colony burrows are opened by some chance, and the inhabitants exposed to the attack of their arch enemies, the true ants. Their relatively enormous, hard heads serve to block up passageways, while their mandibles or jaws serve to destroy individual enemies. Protected thus from flank attack, they are extremely effective. When outflanked, however, their clumsy movements and unprotected bodies and legs make them easy prey for true ants but a small fraction their size. Other Insects Commonly Confused with Termites The small size and social habits of termites have caused them to be associated with ants in the public mind. In structure, the true ants are very different from termites ; the ant may always be distinguished by the possession of a narrow waist, while the termite is large-waisted. In life history, the termites differ in lacking the larval and pupal stages of the ant. A young termite is much like an adult worker save in size. In habits also, the true ants and termites differ radically. Termites live shut off from the rest of the world, feeding upon wood, while ants run about in the open and feed upon various materials, being especially attracted by sweets. These great differences in the habits of the two forms mean that they present utterly different economic problems, and are to be con- trolled by entirely diverse methods. Termites certainly are not ants, and control measures that are effective with true ants fail utterly in combating termites. The work of certain other wood-infesting insects is frequently mis- taken for that of termites. Professor E. C. Van Dyke of the Division of Entomology and Parasitology has kindly made the following brief statement with regard to these insects : 1. The true ants, particularly the carpenter ants of the genus Camponotus. The adults are very different from termites, being fully pigmented and wasp-waisted, and the larvae grub-like. The burrowings which are made in dry wood are much like those produced by Kalotermes, but the passageways are always clean, never partly clogged with excretory pellets. 2. The 'powder-post' and 'death-watch' beetles. The adults of these are small and linear or cylindrical and their larvae grub -like. They live generation after generation in old, well-seasoned timbers, honeycombing the wood and reducing it to a condition of powder Circ. 318] Termites and Termite Damage 15 which plugs the old burrows or is expelled from time to time through various shot-hole openings. The very small passageways, the numerous, small external openings and the powdery remnant in their workings help to differentiate them from termite workings. 3. Certain of the larvae of the true wood-boring beetles of the families Cerambycidae and Buprestidae. The work of these, though sometimes very evident and destructive, can be distinguished by the fact that the burrows are always plugged with fibrous f rass or a saw- dust-like material, unlike that of the termites, which is either earthy or composed of pellets. The larvae also are elongate and wormlike. HABIT GROUPS AND DISTRIBUTION OF PACIFIC COAST TERMITES Termites are world wide in distribution within the limits of the tropical, subtropical, and temperate zones. More than twelve hundred species are known. Of these, some fifty are known to live in the United States, and there are but three states from which termites have not been reported. Thirteen species of termites are now known to occur in the Pacific Coast states, all of them being found in California, These thirteen species of local termites belong to six genera included in three families. More importantly, for our consideration, they represent very widely differing habits of life and very different economic possibilities. On these grounds they fall into three distinct habit groups to which we have given common names, which are coming widely into use, as follows : 1. Damp-wood (rotten-wood) termites. 2. Dry-wood (sound-wood) termites. 3. Subterranean termites. Before discussing these groups individually, it should be pointed out that the damp-wood termites are peculiar to the Pacific Coast region and are not of widespread economic importance, and that, being wood-dwellers, they might be lumped with the dry-wood termites. From the point of view of the country as a whole this would seem the better procedure. The blackened portions of the maps, shown in figure 11, indicate the areas of the United States in which serious damage has been reported as done by wood-dwelling termites (fig. lib) and subterranean termites (fig. 11a). It will be seen that, considering the country as a whole, the major problem is that presented by the subterranean termites. The additional group, the damp-wood termites, is conspicuous with us and of considerable local economic importance and great biological 16 University of California — Experiment Station Fig. 11. — Extent of termite damage in the United States; (a) by the subter- ranean termites (Reticulitermes and Heterotermes) and (b) by wood-dwelling termites (Termopsis, Kalotermes, and Neotermes). The maps above are designed to give an idea of the relative areas in the United States subject to damage by the two types. The blackened portions show roughly the areas from which such damage has been reported. For much of this information we are indebted to Dr. T. E. Snyder of the United States Bureau of Entomology. Circ. 318] Termites and Termite Damage 17 18 University of California — Experiment Station interest, and since they present an economic problem different from that of the group into which they would otherwise fall, it has seemed best to give them a separate name. This has already proved of value. Photographs, natural size, of the three types of Pacific Coast termites taken from living groups Fig. 13. — The three types of termites common in the Pacific Coast region vary considerably in size, as may be seen in the photographs shown above: upper, dry-wood termites (Kalotermes minor) ; center, subterranean termites (Reticuli- termes hesperus) ; lower, damp-wood termites (Termopsis angusticollis) . Circ. 318] Termites and Termite Damage 19 Each of the three groups is characterized locally by a species of considerable economic importance, as follows : the damp-wood termites by Termopsis angusticollis, the common damp-wood termite; the dry- wood termites by Kalotermes minor, the common dry-wood termite ; and the subterranean termites by Reticulitermes hesperus, the western subterranean termite. These three economically important species are shown in natural size as they appear in wood in figure 13. The maps in figure 12 give the distribution in California, so far as it is known today, of each of the three habit groups, the damp-wood termites (fig. 12a), the dry-wood termites (fig. 12&), and the subter- ranean termites (fig. 12c). Damp-Wood Termites Distinguishing characters: Our largest termites (fig. 13c) ; winged forms (fig. la) reddish-brown or black-brown, with brown wings, about an inch or more in length with wings; wings twice as long as body. Soldiers (figs. Id and 10a) about % inch in length with large reddish-brown heads and massive black mandibles. Nymphs (figs, lb, lc, and 14) a light yellowish gray-brown, abdomen mottled with dirty gray-brown, head and abdomen large, head considerably wider than thorax, abdomen wider than head. Unused portions of ingested wood deposited as large oval pellets (fig. 27a). The damp-wood termites belong to the genus Termopsis, confined to western North America, and are represented by the widespread Pacific Coast species, the common damp-wood termite, Termopsis angusticollis (fig. 1). These, our largest termites (see figure 13c for natural size), are common in logs and moist or decaying wood in or on the ground along the Pacific Coast from British Columbia into Lower California. They do not enter the ground, and while sometimes found working into sound wood, are dependent upon a constant moisture supply. There are two species, the large or common damp- wood termite, Termopsis angusticollis, and the small or dark damp- wood termite, Termopsis nevadensis. The latter ranges into Nevada and Montana, It may be distinguished from T. angusticollis by the smaller size and much darker color of the alates, by the narrower, straight-sided head, and longer, more slender mandibles of the soldier, and by the larger and more numerous hairs on head and other parts of the nymphs. Its habits are much the same as those of T. angusti- collis but it ranges into higher altitudes, as high as 9,000 feet. T. nevadensis has not often been reported to cause damage to man's handiwork, but this seems to be due to its distribution rather than to any difference in its habits. The large brown winged males and females escape from the colony at about dusk, especially from July to October, usually in small numbers. On the evenings of the warmer days in September they 20 University of California — Experiment Station Fig. 14. — Termite nymphs molt several times. The photograph above shows (&) a reproductive nymph of Termopsis undergoing molt. It casts its entire outside skin (c) , as well as part of the lining of the alimentary tract, and emerges in the last nymphal stage (a) with distinct, pigmented, compound eyes and swollen wing pads from which the adult wings will emerge at the last molt. Fig. 15. — Termites prefer the soft wood grown in the spring and generally leave the hard resin-filled summer wood, as shown in this photograph of a soft- wood pole attacked by the damp-wood termites (Termopsis) in Oregon. Damp- wood termites usually start their attacks in decaying wood and go to sound wood when the supply of rotten wood fails. Some attacks on damp sound wood have been reported. Circ. 318] Termites and Termite Damage 21 emerge in great numbers and in some localities are called 'rain bugs' because of the apparent relation of their swarming to the early rains. They are strong fliers and reach considerable heights, as is evidenced by an attack on the wet wood of a water tank on a seven-story building. While the queen does not develop any great size or egg-laying ability, largre colonies develop, often including several thousand indi- viduals. This seems to be due to the presence of numerous supple- mentary reproductive individuals, which develop in a short time in isolated groups. The nymphs, immature stages of reproductives (fig. lc) and of soldiers (fig. lb), carry on the work of the colony. Those which are to become reproductives bear wing pads in their older stages (fig. 14a). Dry-Wood Termites Distinguishing characters: Intermediate in size (fig. 13a), smaller than the damp-wood termites (fig. 13c) and larger than the subterranean termites (fig. 13&). "Winged forms about % inch or somewhat more in length, with the wings. Soldiers about % to y 2 inch in length; head reddish or brown, about as wide as rest of body, antennae short; mandibles black, toothed. Nymphs grub-like (fig. 5 and frontispiece), pale whitish-gray with variously mottled abdomens; abdomen long and about the same width as head. Pellets (fig. 27b) about half as large as those of the damp-wood termites. The dry-wood termites belong to the genera Kalotermes and Neotermes, and are represented by the common dry-wood termite, Kalotermes minor (fig. 18). The termites of this habit group live, as the name would indicate, in dry sound wood, of trees, poles, posts, timbers of derricks, and of buildings, from at least as far north as Shasta and Mendocino counties south and southeast into Arizona, and Mexico. They rarely if ever enter the ground and the common species require no special moisture supply. There are three species in California, Of these, the common dry- wood termite, Kalotermes minor (fig. 18) is by far the most wide- spread and economically important, It is discussed below. The southern dry-wood termite, K. hubbardi, is common and of economic importance in Arizona but is known only from the extreme south- eastern borders of California. The desert dry-wood termite, Neotermes simplicicornis, has a life habit different from the other two ; it is confined to the desert area (in California) and is found chiefly at or below ground level, and thus usually in damper wood than Kalotermes. 22 University op California — Experiment Station Circ. 318] Termites and Termite Damage 23 Kalotermes huhbardi is responsible for damage to poles and posts, and presumably to houses, in Arizona, particularly in the southern part of the state, and recent investigations by the Termite Investigations Committee have shown it to be the cause of extensive damage along the west coast of Mexico. It is not known to be present in the Imperial Valley region but there is danger of the introduction of it as well as of K. minor as building and irrigation change conditions there. The soldiers of these three species may readily be distinguished by means of their antennae (fig. 17). Those of Kalotermes huhbardi Fig. 17. — The three dry-wood termites are readily distinguished by characters of the soldiers. The soldier of the southern dry-wood termite, Kalotermes huhbardi (a), has an enormous third segment in the antenna, nearly as long as the remainder of the antenna, while the same segment in the soldier of the common dry-wood termite, Kalotermes minor (b) , although considerably enlarged, is not more than as long as the next four segments together, and in the soldier of the desert dry- wood termite, Neotermes simplicicomis (,"..,■,•->; r "-;;. v B&;M ^o■V•:7;:^.,. , Hfei:'*- ra ^gel v mK-'-.. yi ■ '^'> v - '^ , ^'l t ., ■BraiL' ^^B ' *'■•"'•'' m Hg^i\, ■■ '" RPr' w '■'«'- V; r v -V ; Bcv^\ 11 ^'Vv, ■1^ '■ ■- HI BBj^MU BptNf i> ■B'"- : -V '^ sKw3*H§ IH^S PPJL^' M ''■''•*'' m ms^ " v*"' "* ■•"'^t^B*' '■ " A jf 'C-3i' Bfc^fffi J ,<: -?- y **fe T ; *" ^PPn|' ; '"",'^v ' 'v ■ £ ■ ' HRIp^- 4 ■ ■ ; : '^ : ' -HpPPPHB»^>^ *<■?. ,"•-. Bp*3£>.'- "w, Jt ril .?$? Hpr y**-* : ** ' "W •''<■& <: '' v^^^B RiS&t^ ■ irail ^H^lC' ;:; ^wilife^ i&Pl Wmm x ^ : 'r : ^^m BfeP ^ ^a Hgg^PV i **. ^djjjfc**" /xyj '*&*'" iv^a^Ba WS^^ ^./S^j^JUHHH Fig. 24. — The Arizona desert termite, Amitermes arisonensis, common in desert California, surrounds dead desert plants with characteristic earthen galleries, which remain as connecting tubes to puzzle the traveller after the plant is entirely eaten away. Circ. 318] Termites and Termite Damage 33 In general the desert termites, while of great biological interest, are not known to be of economic importance, their food consisting of desert vegetation. One species, however, Amitermes arizonensis, which is common in southeastern California, builds broad covered ways of sand or clay over poles or posts or surrounds dead desert plants with tubes (fig. 24) and has been reported as damaging young citrus trees by eating the bark. This species does no harm to wood over which it builds since it eats away merely the very thin, outer, weathered layer. The smallest species, A. wheeleri, has been reported as doing considerable damage in Texas. Of the potentialities of the others but little is definitely known save that A. calif ornicus has recently been found attacking wood of buildings as far south as Colima, Colima, Mexico. INDICATIONS OF TERMITE PRESENCE OR ATTACK General Signs Termites live a concealed life, but they give external indications of their presence and activities in four important ways : (1) by the failure of wood due to their attacks (figs. 21 and 26) ; (2) by the emergence of the reproductive caste as swarming alates (fig. 23) ; (3) by the characteristic fecal pellets of the wood-dwelling termites dropped from their workings (fig. 27) ; or (4) by the characteristic covered runways (figs. 20, 28), and the towers (fig. 2) or tubes (fig. 30), built by sub- terranean termites from earth to wood or from wood to earth. ml ' a i> Fig. 25. — Termite damage is often lumped with deterioration due to fungus attack under the name 'dry-rot.' The two types of damage are often found together but there should be no difficulty in differentiating between the two. The photographs above show (a) the characteristic checking in lumber attacked by fungus, and (b) the definite cavities eaten out by termites. 34 University of California — Experiment Station Dry Rot Sagging floors and walls and the consequent difficulties with doors and windows are the most commonly noted results of wood failure in buildings. Much wood failure is generally attributed to dry rot. In many cases this failure is actually due to the attacks of termites (fig. 25b) of various types, and it seems possible that some of the actual dry-rot damage is due to the introduction and spread by the termites of the fungus and the moisture necessary to its development. a b Fig. 26. — The wood of houses is sometimes attacked by the dry-wood termites. As seen in the photograph above of the work of the common dry-wood termite (Kalotermes minor), they eat up to the paint itself, leaving cavities which yield at once to pressure. This specimen is from Suisun in the upper San Francisco Bay region, where such work is uncommon. The dry-wood termites are most numerous in the southwestern region of the United States and along the Pacific Coast into northern California (see fig. life). &?qfrW'j& Fig. 27. — The workings of the wood-dwelling termites are characterized by accumulations of the tiny impressed fecal pellets shown in the above photographs twice natural size. The pellets of the damp-wood termites (a) are much larger than those of the dry-wood termites (&) ; the latter are more regularly formed. Circ. 318] Termites and Termite Damage 35 Signs of the Damp-Wood and Dry-Wood Termites The work of the wood-dwelling termites is often indicated in its later stages by weak points in the wood where the galleries come close to the surface (fig. 26). Deeper galleries may be detected by tapping. Incipient colonies are rarely discovered without destruction of the wood. Fecal pellets (fig. 27) present in the wood or near it, indicate that it is the damp-wood or the dry-wood termite rather than the sub- terranean termite, since the latter does not produce pellets. The pellets of the damp-wood termites are larger and less regularly formed than those of the dry-wood termites. Fig. 28. — Tubes and covered ways, projecting the conditions of the colony home in the earth to their workings in wood, are characteristic features of the activities of all subterranean termites. These are composed of tiny particles (&) of earth or partly digested wood. The western subterranean termite, Beticuli- termes hesperus, builds these very extensively in southern California but rarely does so in the central and northern portions of its range. That it can do so is indicated by the photograph (a) which shows the runways built in a single night in the Termite Committee's laboratory in Berkeley by termites removed from ground connections, 36 University of California — Experiment Station Signs of the Subterranean Termites Aside from a general failure of the wood, the work of subterranean termites is indicated in many cases either by a frayed-out condition of the wood at ground level or, especially in the southern part of the state, by the characteristic earthen-like covered ways and tubes (figs. 20, 28, 30). ' 1 ESI Miff ' '^Isr--^ lit! P i >.^RF~ 1 Fig. 29. — The work of the subterranean termites can always be recognized by reason of the peculiar 'frass' of earth particles or partly digested wood used to plug up unused galleries and to wall off other cavities. This is often accompanied by spotting of the wood with deposits of liquid feces. The sub- terranean termites never produce the pellets which are characteristic of wood- dwelling termites. The above photographs show this characteristic 'frass' under different conditions. Plugs and other masses of earth-like frass within the galleries or along the surfaces of wood attacked are characteristic of the workings of the subterranean termites (figs. 21, 29). Circ. 318] Termites and Termite Damage 37 The emergence of the small, winged reproductives indicates the presence of an active colony. Those of the genus Beticulitermes, which is found everywhere save in the Colorado and Mohave Deserts, are black. They emerge between 9 a.m. and 3 p.m. on sunny days after the first autumn rains. Fig. 30. — Subterranean termites working in wood far from a ground contact, at times build exploratory hanging tubes, evidently in search of more immediate ground contacts and moisture sources. Those in the photograph, built in the basement of a house in southern California, were over 3 feet in length. 38 University of California — Experiment Station II. PREVENTION AND ERADICATION BY CHEMICAL TREATMENT 5 (For prevention by construction methods see Section III) Note, — The statements in this section cover those points which the author believes will be helpful in determining how to prevent termite damage. They are based upon the results of investigations of the Termite Investigations Committee, some still in progress; in part upon past investi- gations; and are in some cases the personal opinion of the author. The recommendations made herein are tentative and are advanced in the light of admittedly incomplete information on the subject. Both the statements and the recommendations are subject to change as further information is compiled. The methods to be used in the control of termites will depend largely upon the situation found and will be controlled by the value of such treatment to the property owner. The factors governing the method of treatment to be used are, in order of importance : 1. The kind of termite causing damage. a. Kinds common in the locality. b. Frequency of occurrence of termites in the locality. c. Damage to be expected from infestation. 2. The actual damage done to structures with particular attention to damage of the structural or supporting members. 3. Costs involved in : a. Building against termite attack. b. Replacing infested and weakened timbers. c. Application of remedial measures. Several approved methods for termite control are outlined below. These should be used with intelligent modification in each individual case. Though the methods to be discussed have to our knowledge shown satisfactory results, further study may demand revision and change. ELIMINATION OF SOURCES OF INFESTATION An obvious method of reducing the probability of infestation is to remove the possible source. All refuse wood, such as stumps, roots, and dead limbs should be removed. Look for sources of infestation in dead portions of living trees, buildings, fence posts, garden structures, and poles. When infested wood or rubbish is removed, it should be burned at once. Infested wood or poles cannot safely be stored and should not be cut into firewood to be distributed throughout the community. USE OF TREATED WOODe When protection from termites is required for wood in contact with the ground, protection against decay due to fungus will also be s This section was prepared by Merle Eandall, Professor of Chemistry, Chair- man of Subcommittee on Chemistry. fl For use of naturally termite-resistant woods see page 61. Cibc. 318] Termites and Termite Damage 39 desirable. The statements and recommendations made in this section therefore with respect to treated wood for use in contact with the ground should be interpreted as applying to conditions requiring resistance to both fungus and termites. It is considered impracticable to offer recommendations based on the possibility of termite damage alone in cases where wood is in contact with the ground. Treated wood which is to be in contact with the ground should contain a preservative which will not be leached from the timber by the action of rains or ground moisture. The Termite Investigations Committee believes that wood treated with coal tar creosote under pressure and in accordance with the standard specifications of the American Wood-Preservers' Association will give satisfactory protec- tion under all known conditions. Many other wood preservatives and treatments have been submitted to the Committee for investigation and some of them have provided satisfactory termite protection for the period during which they have been under investigation. Since their service records are invariably for periods too short to warrant definite conclusions, the Committee has refrained from publishing any data on the subject. Treated lumber to be used in contact with the ground should be framed before treatment if possible. If it is necessary to cut through the treated wood, all fresh surfaces of the timber should be thoroughly soaked or brushed with hot coal tar creosote (or other equivalent pre- servative) as recommended for this purpose by the manual of the American Wood-Preservers' Association. Where wood not in contact with the ground is not subject to leach- ing, pressure impregnation with zinc chloride, according to the specifi- cations contained in the manual of the American Wood-Preservers' Association, makes a very satisfactory preservative. The use of this material will be governed by the liability of attack by Kalotermes and the value of protection from it. It is estimated that thorough protec- tion by impregnation of the wood with zinc chloride can be gained by an addition of 10 per cent to the building cost. The available information on several proprietary wood treatments shows them to be equivalent in every way to a treatment with zinc chloride, but the length of service of such treatments has not been sufficient to recom- mend them. It is important to know the kind of termite causing damage. The method of treatment will depend upon whether the damage is caused by the dry-wood, damp-wood, or subterranean termite. The type of termite will be indicated by the shape, size, and general appearance of the termite (see fig. 13, p. 18), the kind of runways (figs. 20 and 40 University of California — Experiment Station 28) or galleries it builds, and the presence and type of fecal pellets (fig. 27). PREVENTIVE MEASURES FOR NEW CONSTRUCTION The most satisfactory method of termite control is prevention of termite attack. Proper construction of buildings is the best insur- ance against attacks by termites (see Section III, pages 50-62). • Clear the ground of all wood before starting construction. All refuse wood, such as stumps, roots, and old pieces of wood, should be removed from the site. All termite-infested wood refuse should be burned immediately. Additional protection can be gained if the ground of the building site, particularly within the bounds of the foundation, is treated. Treatment of the soil with one of the ground treatments (see page 46), before the house is built, is helpful. CONTROL OF DRY-WOOD TERMITES IN OLD STRUCTURES Dusts The most efficient method of dealing with Kalotermes infection thus far found is by blowing dust into the tunnels. Either paris green, finely divided white arsenic (arsenical smelter dust), or finely ground sodium fluosilicate powder may be used. Paris green and arsenical smelter dust are more poisonous than sodium fluosilicate and extreme care should be taken to avoid breathing or swallowing the dusts of these substances. If the dust inadvertently gets on the skin, it should be thoroughly washed off without delay. If it gets in the eyes it should be washed out with a 5 per cent boric acid solution, and if a quantity is accidentally swallowed, give an emetic and call a physician. The Termite Investigations Committee has drawn up the following tentative specifications for the application of poisonous dusts : In applying the dust a small hand duster such as is used in small gardens is most effective. The type with the container for the dust forming an extension of the blowing chamber and with the nozzle in line with the plunger is the most convenient. A rubber stopper (see fig. 31) should be placed around the nozzle so that when the nozzle is inserted in approximately a 14-inch hole, a tight joint will be made. Quarter-inch holes should be bored in the infested timber at from 3 to 6-foot intervals so that the holes cut through the termite galleries and go from one-half to three-quarters of the way through the wood in its largest dimension. A little practice will enable the operator to determine while boring when the bit strikes the gallery. The duster Circ.318] Termites and Termite Damage 41' is then inserted in the hole and given three or four strokes and the hole plugged with a wooden plug or small cork. In dealing with interior work a hole as small as y 1Q inch can be used provided a suitable nozzle is available. METHOD OF TREATING TERMITE INFECTED TIMBER WITH POISONOUS DUST Fig. 31. — The dry-wood termite once established may best be combated by means of poisonous dusts spread through the colony by the termites themselves. The termites have a habit of licking one another, thus transferring dusts one to the other. The best methods known at present for applying such dusts are illustrated above and in figure 33. It must not be inferred from figure 31 that a hole bored as directed will cut only one termite gallery. The schematic diagram shows only one gallery broken into, but this is seldom the case. Usually many termite galleries are cut by any hole bored into infected timber, but it is best to bore the hole for treatment into the greatest dimension of the timber because that increases the chance of cutting termite galleries. Certain dusts are effective. The Termite Investigations Committee has used paris green, finely divided arsenical smelter dust, and finely divided sodium fluosilicate. These are tentatively suggested. The Committee is desirous of receiving information as to the effectiveness of these chemicals when used according to specifications. 42 University of California — Experiment Station Of the above poisons, finely divided arsenical smelter dusts seems to give the most rapid kill. Paris green is second and sodium fluo- silicate the slowest. Sodium fluosilicate is to be preferred, however, when dwellings or places near habitations are treated, because it is relatively non-poisonous to human beings. Poisonous dusts do not kill immediately. They are slow poisons. All the members of the colony should not be expected to be dead before two weeks. It is important that each colony be reached. Each separate system of runways must be dusted, although it is unnecessary to dust each runway. The poison is distributed through the colonies by the termites them- selves. Referring to figure 31 it will be noted that the termites groom one another. They do not seem to mind the dust in their tunnels and will walk through it, thus dusting the many hairs which cover their bodies. In this manner the poison is spread through the runways much more effectively than has been possible by any mechanical means. One insect carrying poison on its body will kill many. Dust may not be entirely effective in wet wood. It becomes caked in moist runways. Control by means of dust depends upon the adher- ence of the fine dust particles to the hairs of the body of the termite. In moist runways, therefore, the efficiency of dusts may be decreased. Paris green and arsenical smelter dust are poisonous to man. Use reasonable care in handling these substances. Before meals the operator should change his clothes, wash exposed parts of the body in 25 per cent solution of sodium thiosulfate (photographer's hypo). If the poison should be swallowed give an emetic and call a physician. Cleanliness while and after handling the dusts is essential. FUMIGANTS Fumigation is not very effective in killing dry-wood termites. It does not compare in effectiveness with the dusting processes outlined. Tests of pole stubs infested with termites placed in airtight chambers for 24 hours with extremely high concentrations of hydrogen cyanide gas show this treatment to be ineffective more than 1 inch from the surface of the wood. Cyanide fumigation is not recommended because of its ineffectiveness and its extremely poisonous nature. Some other materials which have been used as fumigants are ortho-dichlorbenzene, carbon disulfide, carbon tetrachloride,. and benzol, named in the order of their value. Ortho-dichlorbenzene has the advantage of being safe to use and handle, as well as being the most effective of these materials CiRC. 318] Termites and Termite Damage 43 for killing termites. The liquid ortho-dichlorbenzene should be injected into the galleries under pressure. Carbon disulfide and benzol are dangerous to use. They are highly inflammable, volatile liquids. When using these substances it is very important to make sure that all open flames in the vicinity are extinguished. Through the accidental ignition of these vapors danger- ous and fatal explosions have occurred. Carbon tetrachloride, carbon disulfide, and benzol actually differ very little in their power to kill termites. The use of carbon disulfide and benzol as fumigants is being discouraged because of the very poisonous nature of their vapors and the possibility of fires and explosions. Paints The true effectiveness of paints in preventing damage has not yet been definitely established, but they certainly diminish and retard destruction by the dry-wood termite. One method of protection for the portion of uninfested structure above ground against infection by dry-wood termites is to apply a thorough coat of standard paint. Especial care should be taken to putty all exposed nail holes and cracks in the woodwork. Infestations of Kdlotermes have been observed in the lower end of trims of window casings and doors where the trim is in contact with the casing. These infestations are back of the point reached by paint. A chalky or soft paint film is quite ineffective as protection. Recent tests show that the addition of poison probably does not increase the effectiveness of gilsonite paints. Just how hard a paint film termites are able to penetrate has not been determined, but termites have been observed to penetrate standard two-ply roofing felt which was applied with two workman- like coats of standard asphalt, The termites in this case apparently threw the chewed-off fragments of asphalt and felt to one side. In regions where the dry-wood termite is prevalent all accessory wooden structures should be painted. If termites are found dust treat- ments should be used (see pages 40, 41). Paints and sprays are not effective in killing termites in infested wood. Tests recently made by the Committee show that substances painted or sprayed on the surface of infested wood, though the materials may be extremely poisonous to termites, fail to kill the insects in the interior of the timber. 44 University of California — Experiment Station CONTROL OF SUBTERRANEAN TERMITES IN OLD STRUCTURES The most satisfactory method of preventing- damage by the sub- terranean termite in existing buildings is to remove all untreated wood from ground contact by means of a good concrete, or a properly treated wood foundation. Complete insulation from the ground of all untreated wood is the only permanently effective preventive or remedy against attack by subterranean termites. See Section III. ^r^vu k TREAT WITH HOT CREOSOTE OR. EQUIVALENT PRESERVATIVE- UN PEP PRESSURE: P1ER_ blQCK FOUNDATION CREOSOTE 15 MOST EFFECTIVELY USED AS A PALLIATIVE AGAINST THE SUBTERRANEAN TERMITE AT THE JOINING SURFACES OF WOOD ON WOOD OR WOOD ON CONCRETE-,, Fig. 32. — Preventive measures may best be taken at the time of original construction. One of the proved methods is pressure impregnation with coal- tar creosote or equivalent preservative of wood to be placed in, on, or near the ground. Where this has not been done and termites are attacking wood or such attack is feared, creosote may be effectively used as a palliative measure as illustrated above. Subterranean termites in wood which has been insulated from ground contact die. They must maintain contact with the ground to obtain the moisture necessary for their existence. When contact with their moisture supply in the earth is cut off, insects in the damaged wood, no matter how numerous, soon dry up and die. Proper ventilation under a house is essential and should be pro- vided, since it is helpful in preventing fungus attacks on timbers of the substructure. The termite always works under cover, and, there- fore, effective ventilation of itself will not curb the activities of the subterranean termite. Circ. 318] Termites and Termite Damage 45 Where it is impractical to rebuild the foundation, other steps can be taken. Remedial measures may be resorted to, such as treating the timbers with creosote, sodium arsenite solution, or poisonous dusts (as recommended for the dry-wood termite) and treating the ground near them with a solution of sodium arsenite or other poison. These treat- ments, however, may not be effective in reaching and destroying the colonies. Treatment of Foundations Subterranean termites often use cracks in brick or masonry foun- dations as runways. A common method of treatment is to inject a generous amount of hot creosote. Where creosote or some other wood- preserving oil is used as a palliative treatment an attempt should be made to inject the material between the surfaces of the foundation and the infested sill, and between the surfaces of sill and studding (fig. 32). Another method of handling this situation is by blowing poisonous dusts into the cracks and sealing them with hot asphalt or dry cement grout. Poisonous Dusts The use of poisonous dusts, as suggested for the dry-wood termite, is now being tested by the Termite Investigations Committee with relation to the subterranean termite (Reticulitermes) and the damp- wood termite (Termopsis). Experience shows, however, that through the combined destruction of rot and termites the wood is often so nearly destroyed that it is impossible to apply such a treatment. Timber attacked to such an extent should be replaced. Superficial Treatment of Timbers Not Effective Superficial sprays of creosote or other insecticides are not effective. They may be effective as a temporary preventive against new infes- tation but are certainly not effective in killing termites already in wood. Extreme caution should be exercised when compressed air is used in spraying in or under houses. In applying paints which contain oils or creosotes, by means of a spray, indcors or under houses, it should be remembered that the mist produced by such a spray is highly inflammable. It is therefore important that there be no open flame or pilot lights in the vicinity, in order to avoid dangerous explosions. It is advisable to wear masks, goggles, and gloves while applying poisonous or corrosive substances. Such equipment adds much to the 46 University of California — Experiment Station safety of the operator. Protective appliances which have become saturated with the poisonous material should be discarded. Cases of injury to operators have been traced to neglect of this point. The effectiveness of poisonous paint as a preventive is question- able. It is common practice to spray the joists and sub-flooring of substructures with a poisonous bituminous paint as a protection against the subterranean termite. Under laboratory conditions termites are able to penetrate a film of poisonous bitumen paint and survive. Under field conditions we have only meagre observation on this subject. Though such a treatment cannot be called worthless^ it must be remembered that the flat surfaces which receive paint are not the common points of entry for the termite. Termites usually enter where one timber is in contact with another. These points (crevices and nail holes) can be thoroughly treated only at the time the struc- ture is built and seldom receive any protection from the application of a coat of paint after the structure is completed. The addition of poison to such paints, as a. further safeguard, is, on present evidence, of questionable value. Ground Treatment Ground treatment is the palliative measure most used against the subterranean termite. The treatment consists of soaking the infested soil with some material which is poisonous to the termite. It is important that all wooden forms, stumps, or pieces of wood under the structure be removed before applying any form of ground treatment. The most commonly used ground treatment is a 10 per cent solution of sodium arsenite. As sodium arsenite is poisonous to plants and animals it is recommended that, instead of being sprayed promiscu- ously over the ground surface, the solution be used only where it is necessary. When an infestation is found, the surface of the ground should be broken up and drenched with a 10 per cent solution of sodium arsenite. A conspicuous warning that the ground has been poisoned with sodium arsenite should be left in the form of a perma- nent sign of wood or metal fastened securely to a permanent structure. A 10 per cent solution of sodium arsenite is recommended in accordance with present practice and the recommendation of the United States Department of Agriculture (see Farmers' Bulletin 1472). It is the opinion of the Termite Investigations Committee, based on incomplete laboratory tests, that a much weaker solution will be effective, with less danger to public health. The only possible loss by the use of a solution weaker than 10 per cent is a shortening of the length of time the treatment will be effective. Sodium arsenite Circ. 318] Termites and Termite Damage 47 is soluble and will leach out of the ground if applied in places near running' water. Sodium arsenite is dangerous when in contact with the skin or eyes and special care should be taken in handling the solution. Should it be spilled on the skin, wash first with a 25 per cent solution of sodium thiosulfate (photographer's hypo) and then wash thoroughly with water. If any of the material gets in the eyes it must be washed out immediately with 5 per cent boric acid solution. Ten per cent sodium arsenite is prepared by mixing 1 gallon of commercial 40 per cent solution with 4 gallons of water. The arsenite pail should be used for no other purpose. On account of the danger involved in the use of sodium arsenite, several substitute methods have been proposed. The efficiency of these treatments has not been definitely established and the Committee is very anxious to obtain information on this point from those who use the following methods. These non-toxic ground treatments are applied by drenching all the soil within the foundation walls. As these solutions are inexpen- sive, it is suggested that they be applied generously for best results. Care should be exercised if garden plants are growing near the foundation, as all these materials are somewhat toxic to plant life. 1. Apply as above a 10 per cent solution of copper sulfate made by dissolving 4 pounds of blue vitriol crystals in 5 gallons of water. The solution can be made conveniently by putting the blue vitriol in a small sack and suspending it in warm water. Copper sulfate solution is corrosive to iron or galvanized iron equipment ; hence wooden pails should be used in mixing and handling this solution. Copper sulfate is a good protection against fungus. 2. Apply a solution of borax (2 pounds of borax in 5 gallons of water) in a manner similar to the above. Borax also is a fungicide. 3. Apply a solution of 4 pounds of magnesium fluosilicate in 5 gallons of water as above. 4. Apply a solution of zinc chloride, 4 pounds of zinc chloride to 5 gallons of water, as above. None of the ground treatments will be effective unless extreme care is taken to remove the wood in contact with the ground and unless the ground is thoroughly saturated with the solution. It should be noted that all these materials are water-soluble and therefore subject to leaching. After the ground treatment has dried it is not advisable to disturb the treated surface except where sodium arsenite has been applied. 48 University of California — Experiment Station When sodium arsenite is used, it is advisable to rake soil over the treated spots as a protection against accidental poisoning-. The non- toxic ground treatments, if properly applied, will be most effective undisturbed. PREVENTING ATTACK ON NEW POLES AND POSTS In regions where the dry-wood termite is not prevalent a creosote butt-treatment will protect a pole or post against termite attack. The few cases of damage to butt-treated poles by damp-wood or subter- ranean termites have been traced to mechanical injury of the treated portion, or to a change in grade after the installation of the pole which brings the dirt fill above the treated pole butt, or to checking which took place subsequent to treatment, In regions subject to the attack of dry-wood termites a full-lengh treatment of poles or posts with a non-water-soluble preservative is recommended. Creosote has been used extensively for this purpose. The installations of full-length creosoted poles (both open tank and pressure treatments) are not yet old enough to demonstrate the life of service to be expected from them. The service records of standard pressure creosoted lumber indicate, however, that this treatment applied to poles should meet all requirements. REMEDIAL MEASURES FOR INFESTED POLES AND POSTS Treatments are recommended for infested poles. The Termite Investigations Committee has been successful in the use of poisonous dusts as outlined above for combating the infestation of dry-wood termites in poles and posts. Satisfactory results have been obtained by boring the holes for treatment 3 feet apart and spacing them at 120° angles around the pole (see fig. 33). The Committee is recom- mending for experiment, treatments with poisonous dusts, (a) 3 feet apart, (&) 6 feet apart, and (c) applied only where infestation is found. The Committee will appreciate reports of the results of experi- ments with poisonous dusts, including the following data : ( 1 ) type of termite found, (2) poison applied, (3) description of treatment and spacing, (4) condition of wood (dry or moist), (5) weather con- ditions at time of treatment, (6) cost of material, and (7) cost of labor. Note. — The Termite Investigations Committee is anxious to accumulate detailed information on the use and effectiveness of the treatments outlined in this section, under varied conditions. Those who use these treatments and are willing to cooperate with us in the compiling of these data may obtain forms for reporting the information by writing to the Subcommittee on Chemistry, Termite Investigations Committee, 103 Gilman Hall, University of California, Berkeley. Circ.318] Termites and Termite Damage 49 DRILLED HOLE DRILLED, HOLE \ INCH HOLES APE DRILLED INTO INFECTED POLE AT THREE FOOT INTERVALS DRILLED HOLE 120 CUT SECTION OF POLE SHOWING % INCH DRILLED HOLES INTO WHICH THE POISONOUS DUST IS FORCED Fig. 33. — Treatment with poisonous dusts seem to afford a satisfactory method of eliminating infestations of dry-wood termites in trees, posts, poles, and large timbers. The method recommended for poles is illustrated above. It may prove possible to accomplish extermination with a wider spacing of treatments. 50 University of California — Experiment Station III. PREVENTION BY CONSTRUCTION METHODS 7 (For prevention by chemical methods see Section II) Note. — The statements in this section cover those points which the authors believe will be helpful in determining how to prevent termite damage. They are based upon the results of investigations of the Termite Investigations Committee, some still in progress; in part upon past investi- gations; and are in some cases the personal opinion of the authors. The recommendations made herein are tentative and are advanced in the light of admittedly incomplete information on the subject. Both the statements and the recommendations are subject to change as further information is compiled. Construction methods designed to obviate termite damage in build- ings may be classed as (1) preventive, and (2) corrective. In the preventive class is new construction with proper details to prevent damage. In the corrective class are alterations or repairs to eliminate and stop damage which has already started. The following recom- mendations are results of consultation with building inspectors, archi- tects, and engineers, and represent what is believed at present to be the best practice. The Committee will welcome further suggestions on structural details. NEW CONSTRUCTION The principal cause of damage by subterranean termites is improper construction. There are several points or details in building which should be carefully checked in erecting a structure to prevent attack. It is not so much a question of what materials are used ; it is a question of how to use these materials correctly. A little precaution and possible slight increase in original cost will prevent annoyance and further expense later. Foundations should be of dense well-placed concrete; solid-unit masonry laid in Portland cement mortar with well-filled joints, or wood thoroughly impregnated by a standard pressure process with coal-tar creosote. Hollow construction should not be used unless the tile cores are filled with properly mixed concrete or unless corrosion- resistant metal plates are used to entirely seal the hollow cores from the construction above. In planning a foundation wall, whether or not a cellar is con- templated, keep the ground level on the outer wall at least 6 inches from the top of the foundation. It is better to increase this distance if possible. 7 This section was prepared by F. G. White, Chief Engineer California State Board of Harbor Commissioners, Chairman Subcommittee on Engineering and Specifications of the Termite Investigations Committee, in collaboration with Walter Putnam, City Superintendent of Building of Pasadena, Chairman Sub- committee on Building Construction Details. Circ. 318' Termites and Termite Damage 51 Wherever foundation walls meet or intersect they should be adequately tied together with steel rods (fig. 34). This is to prevent the opening of joints or cracks due to shrinkage of concrete during setting. (This shrinkage always takes place.) Chases or slots may be left in the concrete foundations to receive the ends of girders. Wherever this condition occurs adjacent to an earth fill under a concrete covered porch or elsewhere, care must be exercised that the concrete around this opening is dense and that the sides, top, and ends of the timbers are not in contact with the concrete. It is recommended that those portions of timbers which rest on con- crete be coated with hot coal-tar creosote. In no case should the timbers extend through the concrete foundation. 6 MINIMUM FOUNDATION WALL GROUND LINE- Fig. 34. — A recommended type of foundation wall, (a, a) Steel rods, all splices lapped at least forty times the diameter of the rod. In ordinary cases 14 -inch square, or %-inch round, rods are sufficient. These rods prevent cracks from extending up through the foundation. Such cracks if allowed to form are ideal runways from the ground to the bottom of the sill. These rods should be used in both concrete and masonry walls. Stucco on an exterior wall, if finished to the ground level, should be properly anchored to the foundation wall. Numerous cases have been found where the stucco became loosened from the foundation wall and the space thus formed was a well-concealed runway for the sub- terranean termite from the ground to the structure. Before applying stucco to the foundation wall, see that the surface of the wall is free from soil and that it presents a clean, rough surface (fig. 35). In the designing and constructing of concrete or brick patios, porches, or steps, care should be taken to completely seal these struc- 52 University of California — Experiment Station STUCCO ** ' STUCCO — REINFORCING S&&?/ HEADER, SUB FLOOR. zaszagzz zzzzzzzzgZ2ZZ22ZZ22zzsgaazazazzzzzzagzgz^ ^ Fig. 35. — How the stucco may be applied to secure anchorage to foundation wall, (a) Galvanized No. 14 wire not over 6 inches on center tied to stucco reinforcing, (b, b) Reinforcing rods. These ties may be separate wires or mesh placed in the forms before concrete is poured or placed in the joints of unit masonry. t/A ^ CONCRETE S a.. SOLE PLATE ^ SUB FLOOR. SazZZ2ZZZZZ2ZZ3ZZZZZZZZZZZZZgg> @1>f ^■• foundation ;- $* Fig. 36. — This detail recommended where joists are parallel to wall at porch. (a) Corrosion-resistant metal plate as in figure 37. (b, b) Reinforcing rods. (c) Short joists set 16 inches on center extending from wall to nearest joist. (d) Two-inch by 3-inch braces fitted between short joists. Circ. 318] Termites and Termite Damage 53 tuxes from the building proper. See that the top of the foundation wall is above or at least level with the top of the floor of the patio, por.ch, or the highest step (figs. 36 and 37). This is an exceedingly common point of attack. Where planting areas in patios or porches are contemplated, it is essential that proper construction methods as in figure 36 be used. It is necessary to seal the building from such areas. The use of reinforced concrete slabs for exterior porches is recom- mended where the cost is not too much in excess of the cost of the WALL < Fig. 37. — This detail recommended where joists are perpendicular to wall at porch, (a) Corrosion-resistant metal plate extending in front of and under joists and sill, (b, b) Reinforcing rods. Use cross-bridging instead of the usual solid header so that all surfaces are ventilated and inspection is easy. concrete slab placed over an earth fill. Where reinforced concrete slabs are used, an opening of suitable size should be left in the main foundation of the structure to allow for the removal of all wooden forms under the slab. It is advisable where possible to place one or more ventilating openings in the porch walls to provide proper venti- lation for the area under the reinforced concrete slab. If wood posts are used the bottom of the post should never be below the finish floor when the floor is of concrete or similar material resting on the ground. The post should bear on a corrosion-resistant metal 54 University of California — Experiment Station plate, at least as large as the bottom of the post, with a tight-fitting metal dowel through it (fig. 38). Where concrete floors are to be laid on the ground, great cfare should be used to prevent the formation of joints or cracks which will provide concealed points of entry to any wood (figs. 39 and 40). The concrete should be mixed to make as dense a mixture as is possible. "wVa. POST v fry CONCRETE SLAP :"L\ •'« !■■';. ' : C ■ - • • JL if;".. \i % X8 METAL ^ DOWEL CORROSION RESISTANT METAL PLATP NOT LESS THAN ONE INCH /T^T II v.- TOUNDATIQN '• Fig. 38. — Wood-post foundation detail. Use vertical sides (a) here, so that slight settlement of floor slab will not crack it. Do not bring concrete slab down to shoulder of foundation. /CttPS f&9\ HOT LESS THAN ONE INCH Fig. 39. — Detail of concrete floor at partition. The dimension A should be great enough so that the joint between the floor slab and the foundation is not covered by the base. The bottom of the plate should never be below the top of the finish floor. Pipes that come up through a foundation or a concrete floor into a concealed space should fit tightly in the concrete. Be sure no open- ings, however minute, are left in the concrete around the pipes. No Circ. 318] Termites and Termite Damage 55 construction joint should be permitted under any concealed space or wood unless the two members are securely tied together with reinforc- ing rods or the joint is sealed with a sheet of corrosion-resistant metal (figs. 41a and b). wire full- length of partition And tied into all intersecting- walls Fig. 40.— -Where the location of the partition is not known before slab is laid, the entire slab should be reinforced as shown and tied to surrounding walls. rT^TY^I i! PLAN 3 RODS TWO RODS I I I I PLAN TWO RODS ( TWO PODS I HOLES ■bjlp o o fa-. '•'• \ PLATE- S 1 >'..'.<= ■;-c>' 1 PLAN K-Lh'H- ELEVATION ELEVATION a b Fig. 41. — Construction detail at foundation wall intersection (a) using tie rods; (b) using metal plate. ALTERATIONS AND REPAIRS Subterranean termites require more moisture than seasoned wood will furnish and the only important source of supply is the ground. As a consequence they must maintain a ground connection. To main- tain this connection they build covered runways from the ground to the wood or utilize concealed cracks or crevices for this purpose. One 56 University of California — Experiment Station of the primary objects in all alteration and repair work should be to close all hidden points of entry. Structures should, therefore, be carefully inspected at regular intervals and when termite colonies are found their runways should be destroyed and the ground around the colony should be treated to destroy them (see pages 46-48). If foundation walls are cracked and it is thought that termites are entering through these cracks, there are several inexpensive methods of repair (figs. 42 and 43). crack Side elevation gi3 SECTION Fig. 42. — Method of repairing cracked foundation wall. Drill a hole (a) through the wall following the crack, clean out the hole and thoroughly wet the masonry. Then fill the hole with a rich dense Portland cement mortar. Use only enough water in this mortar so that it will make very fragile balls when compressed in the hand. Put a little mortar in the hole and ram it solid with a hammer and iron rod, repeating the process till the hole is completely filled. 2 SILL CORgQSlON RESISTANT \ METAL PLATE I, Side elevation Fig. 43. — Another method of repairing cracked foundation wall. Cut a hole (a ; clear through the wall. Place a piece of corrosion-resistant metal (b) the full width of the wall lapping about 2 inches on each side of the crack in the bottom of the hole and fill the hole as directed under figure 42. If the termites are coming up through a crack in a concrete floor the method of repair shown in figure 44 may be used. A common but improper method of construction where concrete porches and steps are built around houses is shown in figures 45 and 47 and a recommended method of repair which is usually successful is shown in figures 46 and 48. When it is desired to use stucco over an original siding of shingles, shakes, or siding, it is recommended that the original exterior siding be removed below the top of the foundation wall (fig. 49). Circ. 318] Termites and Termite Damage 57 If it is necessary to extend the stucco to the ground line, place a corrosion-resistant metal plate between the sill and the top of the foundation wall. The outer edge of the metal plate should be so placed that it will be imbedded in the stucco. Do not use furring strips on the foundation wall. It is necessary to secure a mechanical bond (vW^^Y^V^ COSPOSION RESISTANT METAL PLATE SOLE PLATE SECTION PLAN Fig. 44. — Cut a hole (a) about 4 inches wide and 2 inches or 3 inches deep in the floor under the partition as shown, being careful not to crack or shatter the concrete in the bottom or sides of the hole, clean it out, and thoroughly- wet the concrete. Then place a sheet of corrosion-resistant metal which covers the entire bottom of the hole. Then fill the hole as called for in figure 42. 58 University of California -Experiment Station H TILL >4 «>. £y\ Fig. 45. — The earth fill in contact with the sill and solid header is not only a standing invitation to the termites, but is also sure to induce fungus attack. (Compare this with fig. 37). Composition roofing placed between the earth and wood is no protection, because termites will readily penetrate asphalt and coal-tar pitch. CONCRETE SL AB 7^ SOLE PLATJE- SUB FLOOR. Fig. 46. — This is the method of repair for the construction shown in figure 45. (a) Two-inch by 2-inch piece set on end at each joist, (b) Continuous corrosion- resistant metal plate extending under sill and 2 inches into new concrete, (c) Continuous corrosion-resistant metal plate set before concreting. Circ. 318] Termites and Termite Damage 59 ^ concrete slab : Sole plate SUB FLOOR. Fig. 47. — This is the common construction where the joists are parallel to the wall. The method of correction is shown in figure 48. Fig. 48. — This is the method of repair recommended for the construction shown in figure 47. (a) Two-inch by 3-inch braces fitted between short joists. (&) and (c) Continuous corrosive resistant metal plates set before concreting. 60 University of California — Experiment Station between the stucco and the foundation wall in order to properly seal this space against undetected termite passage. The exterior of the foundation wall should be clean and clear of soil, paint, and other loose particles to insure a good bond (fig. 49). sheathing } ORIGINAL SlPINq - STUCCO REINFORCIN STUCCO } 5QLE PLATE SUB FLOOR i7i/ir/}////s///rrf//i/s/fffsst/fsssfSj////i//ti//r/(r,///sist,ii)?fHt}r. ^CORROSION PESISTANT METAL PLATE- JOISTS 16 O.C. wwm y/rr Fig. 49. — Method of placing- stucco over siding on and near foundation wall. SPECIFICATIONS FOR MATERIALS Metal Plates Where metal plates are specified, metal for this use may be procured from sheet-metal shops or hardware stores. The use of corrosion- resistant metal is recommended to insure permanence. Sixteen-ounce (0.021 inches thick) hard (cornice temper) copper is recommended. Hard copper is more suitable than soft copper. Both are used in exterior work on buildings and are easily procured. Soft copper will suffice when hard copper is not obtainable. Brass is suitable for this purpose if it is an alloy of 80 or 85 per cent copper and the remainder zinc. Fifteen gauge zinc (0.040 inches thick) has also been recommended. Galvanized iron may be used. When subjected to moist conditions it will not stand up nearly so long as corrosion-resistant metals. Circ. 318] Termites and Termite Damage 61 Treated Lumber For timber in contact with the ground the most effective chemical preservative treatments are pressure impregnations with coal-tar creosote. For timber not in contact with the ground pressure impreg- nation with zinc chloride has proved very effective where not subjected to leaching. These are the standard chemical preservative treatments recommended by the American Wood-Preservers' Association. Impregnation with preservatives does not mean painting or short- time dipping. Methods recommended by the American Wood-Pre- servers' Association specify treatment under pressure in a closed container so that the preservative penetrates the wood. Dipping timber in a vat containing boiling preservative and allow- ing it to remain for several hours while the liquid continues to boil is another method of treatment which will give some protection, although it is not so effective as treatment under pressure. The liquid should be allowed to cool before removing the timber. Cold brush applications of preservatives are not effective. Hot brush applications are of some slight value for temporary protection. Naturally Termite-Resistant Woods The sapwood of all commercially important species is more sus- ceptible to attack by termites than is the heartwood. The heartwood of some species of timber is more resistant to attack by termites than the heartwood of other species. The relative resistance of the various species of timber has not been accurately determined. The Committee has some data on the subject but both service records and the results of experiments are as yet inconclusive* The causes for variation, as regards resistance to termites, between species of wood and within a species are not known. Many factors seem to be involved. Among those to which the Committee is giving some attention are rate of growth, density, toxicity, moisture content, and conditions of use. Relative resistance may be different for different types of termites. Laboratory experiments indicate that the heartwood of redwood, certain kinds of cedar, and cypress might properly be classed as termite-resistant. Service records of varying durations indicate that the heartwood of redwood and the pitchy heartwood of long-leaf pine might be classed as termite-resistant. 62 University of California — Experiment Station The termite-resistant woods when used in locations not in contact with the ground may be expected to give more satisfactory service than other woods where protection from subterranean termites is desired. This is also true for dry-wood termites, but the evidence on which this opinion is based is not so conclusive as in the case of subterranean termites. Damage by dry-wood termites to wood in contact with the ground is unimportant so far as the records of the Committee show. Damage by subterranean termites to wood in contact with the ground constitutes a major part of our termite problem. The use of termite-resistant woods in such situations will afford some degree of protection. The degree of protection afforded has not been definitely determined. Any of the above mentioned factors may have some effect on the degree of termite resistance. GENERAL RECOMMENDATIONS Eliminate all waste wood. In the case of alteration and repair and in new construction, remove stumps, roots, scraps, refuse, shoring timbers, and refuse wood of all description. Remove all form lumber. All wooden forms on foundations and chimney bases should be removed from masonry work within 15 days ; grading stakes should be removed before laying concrete floors. Barn removed wood containing termites. In repair work it is not necessary to remove all wood that has been attacked by subterranean termites unless it is in contact with the ground or has been so damaged that it is structurally unsafe. If subterranean termites are shut off from any source of moisture supply they will soon die. Removed wood containing termites should be turned at once. Insure adequate ventilation. Adequate ventilation under the first floor should be provided. At least 2 square feet of openings for each 25 lineal feet of exterior foundation wall is recommended. Where there are spaces under floors near the ground they should be exca- vated so that there will be no soil within 24 inches of the joists. Cross- ventilation should be provided. Make periodic inspections. In existing structures careful and intelligent inspections at frequent and regular intervals will greatly reduce the likelihood of termite damage. Such inspection alone or in conjunction with other inexpensive prevention methods mentioned above will in many cases give adequate protection. Circ. 318] Termites and Termite Damage 63 SOME RECENT PUBLICATIONS ON THE TERMITE PROBLEM HOLTMAN, D. F. 1929. Wood construction. McGraw Hill Co., New York. (Chap. VII, pp. 210-30, Methods of preventing termite damage, T. E. Snyder.) Hunt, Geo. M., and T. E. Snyder. 1930. An international termite exposure test. Proc. Amer. Wood Preservers Association. January. Kofgid, C. A., and E. A. Garland. 1929. Mode of attack of the sound-wood termite on a city building. The Architect and Engineer. November. Light, S. F., S. P. Koch, and E. E. Bowe. 1930. How to combat the damp-wood termite. The Architect and Engineer. July. National. Committee on Wood Utilization. 1930. Treated lumber, its uses and economies. U. S. Government Printing Office. Randall,, Merle. 1930. Termites and the retail distribution of treated timber products. Proc. Amer. Wood Preservers Association. January. Snyder,, T. E. 1926. Prevention of damage by termites or white ants. U. S. Dept. Agr. Farmers' Bui. 1472:1-22. Snyder, T. E., A. E. Emerson, and C. A. Kofoid. 1929. Report on the symposium on termite problems of the Termite Investi- gations Committee. Termite Investigations Committee, San Francisco. 64 University of California — Experiment Station TERMITE CONTROL OPERATORS CERTIFIED UNDER CALIFORNIA LAW Under a law passed by the State Legislature of California in 1929, all persons engaged in the state in the business of repairing structures damaged by termites must be qualified and receive a certificate issued by the Agricultural Commissioner of the county in which the work is done. The Political Code of the State of California, Part III, Title V, Chapter YVb, includes : Persons engaged in eradication of pests for hire. $2322 (9). The said commissioner shall have power and authority to pre- scribe and enforce rules for the qualification of any person, persons, firm or corporation, who desires to engage for hire in the business of eradicating or controlling plant diseases, insect or other animal pests or noxious weeds, and to issue certificates to all persons whom he shall find by examination or otherwise to be duly qualified for engaging in such work. Such certificate shall be revocable whenever the said commissioner shall deem such revoca- tion necessary. No person, persons, firm or corporation shall be permitted to engage for hire in the business of eradicating or controlling plant diseases, insect or other animal pests or noxious weeds in this state, who has not first secured a certificate in the manner herein provided. [Stats. 1929, Chap. 145.] Penalty. §2322i. Any person, persons, firm or corporation violating any of the provisions of this act or refusing or neglecting to comply with the require- ments of any legal notices issued under the authority and provisions of this act shall be guilty of a misdemeanor and shall be punished by imprisonment in the county jail for a period not exceeding six months or by a fine not exceeding five hundred dollars, or by both such fine and imprisonment. [Stats. 1923, p. 1208.] 40m-8,'30