%■ z2 Bulletin No. 28— New Series. U. S. DEPARTMENT OF AGRICUL1 L T RE, DIVISION OJF ENTOMOLOGY. INSECT ENEMIES OF THE SPRUCE IX THE NORTHEAST. POPULAR ACCOUNT OF RESULTS OF SPECIAL INVESTIGATIONS, WITH RECOMMENDATIONS FOR PREVENTING LOSSES. Prepared Under the Direction op the Entomologist A. I). HOPKINS, IV. D.. Vice-Director q •■■ mia Agricultural WASHINGTON: GOV E B N M E N l I' B I N TING < » F K I < ' B . DIVISION OF ENTOMOLOdY. Entomologist: L. O. Howard. First Assistant Entomologist: C. L. Marlatt. Assistant Entomologists: Th. Pergande. F. H. Chittenden. Frank Benton. Investigators: E. A. Schwarz. D. W. Coquillett. Assistants: R. S. Clifton, Nathan Banks, F. C. Pratt, Aug. Busck, Otto Heide- lnann. A. N. < "audell, J. Kotinsky. Artist: Miss L. Sullivan. Bulletin No. 28— New Series. U. S. DEPARTMENT OF AGRICULTURE, DIVISION OF ENTOMOLOGY. INSECT ENEMIES OF THE SPRUCE IN THE NORTHEAST. A POPULAR ACCOUNT OF RESULTS OF SPECIAL INVESTIGATIONS. WITH RECOMMENDATIONS FOR PREVENTING LOSSES. Prkparkd Under thb Direction or the Entomologist A. I). HOPKINS. Ph. D.. Vice-Director and Entomologist of thi West Virginia Agricultural Experiment Sot ion. WASHINGTON : G O V E K M M E N T PRINTING O F F 1 C F LETTER OF TRANSMITTAL U. S. Department of Agriculture. Division of Entomology, Washington. D. C. July 1. 1901. Sir: I transmit herewith the manuscript of a report by Dr. A. D. Hopkins, entomologist of the West Virginia Agricultural Experiment Station, on a trip taken in the summer of 1900, under the auspices of this Division, to the spruce-growing region in New England, for the purpose of investigating damage done by insects. The attention of the Department was called to a serious trouble affecting the spruce trees, in March, 1900, and Dr. Hopkins was chosen for the investiga- tion for the reason that he has studied forest insects for many years and is generally known as the leading forest entomologist of the country. His report indicates that he was not only able to determine the cause of the difficulty, but to suggest practical measures of relief. I recommend that it be published as Bulletin No. 2S. new series, of the Division of Entomology. Respectfully. L. O. Howard, Entomologist. Hon. James Wilson. Si cretary of Agriculture. PREFACE. OBJECTS. The primary objects of the investigations were (1) to determine the cause, or causes, of a prevailing unhealthy condition of the spruce in certain sections of the forests of Maine. New Hampshire, and Ver- mont, and to study the prevailing influences found to be favorable or unfavorable to the continuance or spread of the trouble: and (2) to determine, if possible, some practical method by which the owners of the timber could prevent or mitigate the great losses of valuable timber from this cane It is aimed in this report to give a popular account of the investi- gations and the principal results, with recommendations of such methods of prevention or control as seem practical. The details of a technical nature, relating to results of more inter- est to the entomological student or investigator, will be reserved for a special report on this phase of the subject. It is hoped that this popular discussion will be of interest and value to the student and investigator of economic forestry problems, as well as to the practical forester and lumberman. ACKNOWLEDGMENTS. Before proceeding further I wish to express my acknowledgments to all those who have in any way given encouragement and assistance in this work, among whom the following deserve special mention: The executive committee of the regents of the AVest Virginia Univer- sity and the director of the experiment station, for the necessary leave of absence; the Berlin Mills Company, through its president, Mr. W. W. Brown, and vice-president. H. J. Brown, for furnishing transportation and guide from Colebrook. X. H.. across the State to the steamboat landing on the Magalloway River in Maine, and with guides and other facilities during my stay in the spruce woods of the Androscoggin drainage north of the Rangeley Lakes; to the Parma- cheenee Club, through its vice-president, Mr. Henry P. Wells, and manager. Mr. J. A. Dunning, for accommodations at Cam}) Caribou and use of the Forks, Moosebog, Barkers Lake, and Lower Black camps, together with other favors extended; and finally to Mr. Austin Cary, who, as expert forester to the Berlin Mills Company, rendered miiM valuable service through his special knowledge of the Maine woods and the conditions in different sections most desirable to visit for investigation. A. I). Hopkins. CONTEXTS. Page. Outline of trip.. ._ ... 9 The Androscoggin region and its spruce forests 11 Dead and dying spruce . 13 Some characteristics of the dying and dead spruce - — 14 Causes of decay and death . . .. 14 Relation of insects to the trouble. ._ . 15 The spruce-destroying beetle 15 Description of the destroyer .. 16 Life history of the beetle . IT How it passes the fall, winter, and spring _ IT When activitj T commences in the spring IT The summer period . .. ^... 18 Summary of life history . . . _ 18 Explanation of diagram 19 Special features of the beetle's work 20 Kind of trees attacked . . 20 How and when the attack is made . 20 Its work in and beneath the bark ... ... 20 The distinctive, visible evidences of the spruce destroyer's work. _ 22 Pitch tubes. 22 Appearance of the leaves 22 Appearance of the twigs 22 Appearance of the bark and wood 32 Woodpecker work 23 A common fungus on the bark of dead trees 23 The principal natural enemies of the spruce-destroying beetle . . _ 24 A parasitic enemy 24 A predaceous beetle _' 24 Birds as enemies of the beetle 25 A fungous disease of the beetle.. 26 Climatic conditions 26 The principal insect allies of the spruce destroyer 26 The spruce Polygraphus 26 The spruce Tetropium 2T Other insects . ... 2T Historical references 28 Remedies and methods of prevention 30 Review of proposed methods _ 30 Stripping off and burning the bark 30 Destruction of dead trees 31 Girdling trees _ ... 31 Investigation of the girdled- tree method 31 Hack-girdled and peeled spruce . 31 Report on girdling experiments, by Mr. Austin Cary 32 Comments on Mr. Gary's work 40 Suggestions and recommendations 41 Methods of reducing the number of beetles 42 Utilization of dead spruce. 45 Importance of harvesting the matured crop of spruce 46 Summary .... 4T ILLUSTRATIONS. Plates. Page. Plate I.— The spruces of Maine ... : 50 II. — Dendrocton ns piceaperda Hopk. .n.sp._- 52 III.— Galleries and mines of the spruce-destroying beetles 54 IV. — Galleries and mines of Dendroctonus piceaperda in spruce. 50 V. — Old galleries of Dendroctonus piceaperda in spruce. . ...... 58 VI. — Spruce bark showing growth of fungus, Polyporus volvatus .... GO VII. — Cocoons of Bracon simplex, a parasite of the spruce-destroying beetle 62 VIII. — Work of secondary and other enemies of spruce . . 04 IX.— Galleries of Polygraphia rufipenn is, showing different stages 00 X. — Mines of Tetropium cinnamopterum 08 XI.— Work of Xyloterus bhrittatus . ...... .. 70 XII. — Work of Dendroctonv 8 frontalis and Dendrocton us terebrans 72 XIII.— Top of Black Spruce infested with a caterpillar and a plant-louse. 74 XIV. — Dead spruce: also fir and birch 70 XV.— Timber flooded and killed by water on the Magalloway 78 XVI.— Sections of wood cut from Balsam Fir showing rapid growth after the old spruces die or are felled 80 Text Figures. Fi<;. 1. — Diagram illustrating the dormant and active periods of develop- ment of Dendroctonus piceaperda . 19 2. — Trees girdled by different methods 82 8 INSECT ENEMIES OF THE SPRUCE L\ THE NORTHEAST. OUTLINE OF TRIP. ( Mi May 22. 1900, I arrived at Brunswick^ Me., where I learned that Mr. Austin Cary. of that place had gone with a surveying party to near the head of the Androscoggin River, and that, owing to floods and log jams on the upper streams, some trouble would be experi- enced in getting through to where he was located. This necessitated a delay of two days, but in the meantime arrangements were made by Mr. II. J. Brown, of the Berlin Mills Company, for transportation and guides from the railroad at Colebrook. X. II.. until we found Mr. Cary. May 24 I left Portland going northwest through New Hampshire via the White Mountain Notch to Colebrook. Here I was met by two guides sent over from Erral with instructions from the Berlin Mills Company, and on May 25 we left Colebrook, going up the Mohawk River valley ami through the Dixville Notch near its source, thence down Clear Stream To Erral on the Androscoggin. Here we encoun- tered the floods and log jams which prevented further progress by wagon, and the remaining distance to the Brown farm in Maine was traversed on foot and by canoe. May 26, after spending a few hours in the woods studying insect enemies of the spruce, birch, and fir. we went on up the Magalloway River about 15 miles to the Camp in the Meadows where we were met by Mr. Cary. The next morning we proceeded farther up the river to the Forks Camp near the mouth of the Little Magalloway. This brought us into the heart of the northwestern Maine woods and within a few miles of one of the localities in which the spruce were dying. Up to this time the route from Portland through New Hampshire and a small part of Vermont to Colebrook, thence across northern New Hampshire and up the Magalloway in northwestern Maine, led through a region presenting many and varied features of New Eng- land forest conditions, and gave a good opportunity to note in a gen- eral way some of the influences which contribute to the multiplication of insect enemies of trees, as well as those which contribute to their decrease, or even the extermination of certain species which confine their attack to matured timber. No opportunity was had, however, 10 to make a detailed study of any of the problems presented or sug- gested by the prevailing conditions until we reached this place. May 28 we entered the undisturbed spruce forest in the vicinity of Wight's Loggers 1 camps on Twin Brook, where the conditions were found i<> !>e especially favorable for commencing the investigation of a trouble which for forty or fifty years has attracted so much atten- tion and caused the loss of vasi quantities of spruce timber in north- em New England and in New Brunswick. After spending two days here in a thorough examination of a large q umber of infested living, dying, and dead trees, which bore every evidence of having been killed by insects, we extended our investiga- tions further into the forest and across the divide to the Cupsuptic River drainage, and thence across to Lincoln Pond, where extensive summer cutting and peeling of the timber had been carried on. The examination of a great many dying and dead trees, together with a siudy of the conditions in the cuttings, left little doubt as to the primary cause of the prevailing trouble. Indeed, sufficient evidence was found to enable me to suggest to Mr. Cary a possible remedy, in providing girdled trees to attract the destructive insects, thus con- centrating their breeding operations in sections of the forest where, by the ordinary logging operations, the entrapped enemy would be transported to the streams and thus destroyed. The following day we returned to Wight's Camps, and thence went across to Black Cat Brook, Parmacheenee Lake, and Camp Caribou. Three days were spent in the vicinity of this camp, and on June 4 we proceeded to the Little Magalloway, and up this stream to Hamel's Camp. Thence the next day we went to near its source and the sum- mit of Rump Mountain. This route, leading as it did through an extensive burned-over area, recent cuttings, and undisturbed forest, where much dying and dead timber was found, gave an excellent opportunity for the successful prosecution of the investigations. The observations we were enabled to make from the summit of the moun- tain were also of especial interest and importance. We returned to Camp Caribou June 7, where I was joined by Mr. Henry Carter, who had instructions from Mr. Cary to accompany me on an exploration in the heart of the wilderness north of Camp Cari- bou. We started on June 8, going to Little Boys' Falls on the Magallo- way; i hence by trail and canoe to and above .Moose Bog Camp, and i hence by trail via the Game Keeper's Camp to Barkers Lake, which is located near the Canadian line and forms the principal source of the Magalloway. From here we returned by trail to Lower Black Camp and theuce to Camp Caribou, where we arrived in the evening of June 1 1. This trip enabled me to gather much valuable information relating to the distribution of the trouble; the condition of the timber that had been dead live to twenty years; and the relations of old cuttings, 11 blow-downs, and other prevailing features which had a direct bearing on the problem under investigation. Mr. Gary joined me again at Camp Caribou, aud June 13 we pro- ceeded by the old Danforth trail to the Cupsuptic River, and thence to the Stonehouse on the lake near its mouth. From here we pro- ceeded up the Kennebago River and devoted several days to the exploration of the great spruce region at the sources of this and Dead River. This also included a climb to the summit of Boil Mountain where, as from Rump Mountain, an excellent view was had of the prevailing conditions as to dead and living timber over a vast extent of forest. Between Kennebago Lake and Beaver Pond we had a good oppor- tunity to study the conditions in the historic blow-downs of 1871 and 1883, which were followed by great invasions of spruce-destroying insects. We returned to the Cupsuptic Juue 17, and next day I returned to Brunswick and Portland. After making some investigations on Peak Island and in the vicinity of Portland, and reporting to the Berlin Mills Company some features of the results of my investigations in sections of the Androscoggin region in which they were specially interested, I returned home, where I arrived June 29. The specimens of insects and their work collected on this trip num- bered something over 1,700, including 44 species from the Red Spruce, six from the White, and nine from the Black. THE ANDROSCOGGIN REGION AND ITS SPRUCE FORESTS. The Androscoggin drainage north of the Rangeley Lakes and west of the headwaters of the Dead River of the Kennebec, in which the investigations were conducted, is one of great interest, and since the varied conditions prevailing there have a direct bearing on the prob- lems to be discussed further on in this report, it seems fitting and proper that some space should be devoted to its discussion. In this I can do no better than to quote from the writings of Mr. Cary, than whom there is probably no better authority. Indeed, after having gone over the territory with him I learned to have much confidence in his ability as a practical expert forester and a careful and accurate observer of forest conditions. 1 ' * * * These townships [Grafton, Andover. North Surplus, Letters D and E. and No. 6] that I have referred to form a barrier separating the upper from the lower course of the Androscoggin. To the §outh is the lower river, flowing approximately east for 50 miles, catching streams from both sides of its coarse. To the north of that barrier lies the Rangeley Lakes system, again with its axis east and west and about 30 miles in length. The lakes, therefore, situated as they are close under this mountain barrier, receive only trifling tributaries from the south. Their volume is chiefly maintained from the country to the north, which 1 Paper by Mr. Austin Cary, in Third Annual Report of the Forest Commissioner of Maine, pp. 127, 128. 1S96. 12 drains into them by three considerable streams— the Magalloway, the Cupsuptic, and the Kennebago. The outlet of the system is at the west where the river forces a way tor Itself close under the eastern faceof the White Mountains. Attheeast, OH the other hand, the upper lakes are closely approached on the high but elevated land by the headwaters of the Dead and Sandy rivers, which run into the Ken- nebec. Now. as the Rangeley Lakes, with the exception of Umbagog. are about 1,400 feet above the sea. while the country about is, much of it, considerably higher, this Upper Androscoggin country is more elevated than any other area of equal size within the limits of the State. Here on the headwaters of the Androscoggin is the chosen home of the spruce. Continuous with the high land of northern New Hampshire, a part of the great White Mountain plateau, this region in its elevation, its uneven topography, and its climate seems to afford that combination of conditions which ministers to the perfect development of the spruce. The timber of the Appalachian Mountains farther south is not known to the writer. It is a fact, however, that no other part of Maine ever had any such spruce stand, and probably no portion of New York or New England as is found from here across northern New Hampshire. Only patches of timber elsewhere stand as thick as does the country here. Much of the timber too is of the finest quality and size. * Returning again to Parkertown, let me present some figures that will be used in a further discussion of the problems arising in connection with the manage- ment of the Androscoggin land. First is the detailed statement of the trees standing on a sample acre that, fairly representative of the country in its stand ot merchantable spruce timber, was thought to be appropriately such also in respect to the proportion of hard and soft wood in large and small trees. Note particularly the number of large spruce trees as compared with those from 6 to 12 inches in diameter. Their relation is no chance or insignificant matter. Much study has shown it to be characteristic of typical Androscoggin spruce land, while from it are drawn hereafter important practical conclusions: Trees standing on an acreof uncut lain! in Townships, Ranges, Oxford County. Spruce. < tther species. Diameter. i 'A ■i-i I o5 s = > to w Diameter. 4 3 O Q 1* i 6 P. Kst i 7nated volume. Estimated scale. Inches. ( >V.T IS' 14 11 8 is 8 as '.Ml Feet. (■«. ft. 70-90 l.OtHi 7(1 80 600 60-75 210 60-66 135 in 50 170 ;>.-. »:> 35 4U Ft.B.M. 3,500 :i.(NH) 840 502 510 Inches. Over 18... 11 Lfi 12-14 lOandll.. Band 9.... •land 7.... 8-6 Under :: Total. 11 6 •-' 4 3 3 8 4 2 3 :; o 1(1 .-.".I 4 6 8 i:i 3 4 1 .... :; 44 L66 On. it. 1,000 400 200 Ft. B. M. 15 18« 1:.' 11 :::::::::: 10 and ll i 300 200 50 i:*o 90 B and 9 6 and '. Cn. I. 10 Total 191 2,280 7.352 41 49 40 :.'l 1 2,800 4.000 1 < >ne worthless tree In each class. In the estimated scale put upon the sample acre -about 7,400 feet— 5,500, <»r three-quarters of the whole, was in the shape of trees over 14 inches in diameter I feet from the ground. That is a fact to be distinctly marked. Three-quarters of the total spruce in the natural stand of the country is mature — ready in the natural course of things to be cut. Tins is not merely the lumber- man's interest It is the States interest. In timber like this, growth is balan< ed 13 by decay. Dead trees stand scattered throughout it. Upon this very acre there was one. Several more were dying or imperfect, while doubtless several of the '-28 full-grown trees scored are every year decreasing in value. These large, old trees. too, cumber the ground. Producing little themselves they yet, by their shading, keep down the young growth, which could make good use of the room. No one can dispute the lumberman's right or interest in regard to these trees. * *. * The Androscoggin drainage, from the spruce point of view, is the best worthy of study of all the rivers of the State. It is also the one, in my judgment, on which a conservative forest policy is likely to go first into effect. In a letter to Mr. Cary, Mr. J. A. Pike estimates that the spruce then (December, 1895) standing in the Androscoggin basin, at and above Berlin, Me., was 3,000,000,000 feet. He says: This estimate is based largely on personal examination and entirely upon per- sonal knowledge of the territory and th6 character of the growth, and after consulting notes and memoranda extending over a period of more than twenty years. Mr. Cary again refers to the spruce of Maine in a paper read before the Boston Society of Civil Engineers, May 10, 1800, » as follows: It seems probable, then, that 25,000,000.000 feet, board measure, may approxi- mate the amount of spruce woods standing in the State. The total lumber cut in the State in 1896 was something over 600.000,000 feet. Of this, probably 500,000,000 feet was spruce. About two-fifths of this went to the paper and pulp mills. Six hundred million feet is equivalent to 30 feet per acre on the gross area of the State. Five hundred million feet may be 50 feet per acre on the area of what we might call spruce-producing land. These figures are within the amounts which such stands as have been made attached to ordinary cut-over land as its yearly growth. Certain i y they are small in comparison to what we know that scientific forestry has produced elsewhere. The general inference to be drawn from these facts is not a discouraging one. Our resources are still great, and we may feel justified in using them freely. At present the botanists recognize three distinct species of spruce from New England, the Red (Picea rubens), the White (Picea cana- densis), and the Black (Picea montana) (Plate I), all of which were noted by the writer and their insect enemies studied. One of these, the Red Spruce, on account of its size, great value, and prevalence throughout the spruce area, is recognized commer- cially as "The Spruce," while the others, from an economic stand- point, are of secondary or minor importance. DEAD AND DYING SPRUCE. The prevailing condition which attracts especial attention in the upper Androscoggin, is the large amount of dead spruce. It stands in clumps of a few trees to several hundred, and as individuals scat- tered through the forest, or left in the cuttings. In some places the old-felled trunks and tops make travel through the woods exceed- ingly difficult. 'Jour. Assoc. Eng. Soc. Vol. XXIII. No. 3, Aug., 1899, p. 5. 14 While r large amount of dead spruce was observed throughout the area traversed, thai which was then dying, or had died within the past one i«» four <>r Ave years, is Limited to well-defined areas of greater or Less extent, in different sections, bu1 always involving the best stands and Largest t Lmber. The dead Bpruce is not confined to any particular condition of soil, exposure, or altitude, but is found under all conditions, from bogs to high, exposed, rocky slopes, or whenever the trees attain a diameter of over 1- inches. SOME CHARACTERISTICS OF THE DYING AND DEAD SPRUCE. When the t pees commence to die, the first indication in their general appearance is a pale tint of the leaves on the upper branches and tops. These soon fall, even before they lose their green color. When the trees are in this stage of decline, the winder a slight jar, as witli an ax, will cause a shower of the needles to fall, and the ground will be covered with them. After the leaves have fallen, the dead twigs present a reddish appearance, rendering them quite distinct and easily recognized from a distance, when viewed from an elevated point. They gradually assume a Light-gray appearance, followed by a darker gray; then, a few years later — the actual time not yet determined — the twigs begin to fall; Later the branches, and still later the tops break off. Finally, after many years — ten to twenty Or more, depend- ing on the soundness of the base and roots — the decaying trunk will topple over, and contribute to the food supply of the young genera- tion of trees, which have sprung up to utilize the sunlight thus made available. Trees with diseased roots usually fall before they have lost their small branches, and the wood probably decays far more rapidly than in those with sound roots. The only way the declining, dying, and recently dead trees can be recognized from the trail, or in going through the woods, when the tops come between the observer ami the sky, is by the fine dust in the outer bark and moss near the base, the pitch tubes on the bark from near the base up to 10 or 20 feet, the falling or fallen leaves, or the work of woodpeckers. The removal of the outer bark by the birds in search of insects makes the reddish inner bark conspicuous, even on living tires, when they show no other indication of decline. Indeed, the tiers on which the birds have been at work stand out distinct, and can 1m- seen for a long distance in the woods. CAUSES OK DECAY AND DEATH. There are iw<> causes of decay and death, one or both of which affected each of the many hundreds of trees examined: (1) The work of an insect in the bark on the middle trunk, causing the death of the 15 tree; (2) the presence of fungi in the bark and wood. The latter lias been investigated by Dr. Herman von Schrenk, for the Division of Vegetable Physiology and Pathology, and his report has appeared in a bulletin of that Division. Therefore, only such reference will be made to these diseased conditions as has a direct or interrelated bear- ing on the insect problem, and methods of preventing losses from their combined attack. RELATION OF INSECTS TO THE TROUBLE. With very few exceptions x all of the great number of affected trees examined, which were in all stages, from living to old dead ones, throughout the area covered by the trip, showed evidence of depreda- tion by insects; and in nearly every case quite conclusive evidence was found that one species, a bark-mining beetle, had been or was then associated with the primary cause of these unhealthy conditions and death. This evidence consisted in the healed-over burrows in the living bark of healthy, vigorous trees; in broods of this insect which had developed in the bark of living trees during the summer of 1899, the trees yet living in May and June, 1900; in the hundreds of dying and dead trees, with vast numbers of all stages, from young larva? to adults, of this insect under the bark, where they bred the previous summer and fall; and finally its characteristic galleries in the bark, or on the surface of the wood of old dead trees which had been dead from ten to twenty years, while the logs, stumps, and tops in cuttings showed little- evidence of its attacks. In addition to this common and primary enemy of the spruce, many other species of bark beetles, flat-headed and round-headed bark and wood borers, occurred in the dying and dead trees, some following closely the first attack by the primary enemy, others coming later, and still others in succession until the last vestige of the bark and wood is converted back to earth. THE SPRUCE-DESTROYING BEETLE. The observations of the writer lead him to conclude that of all the insect enemies of the spruce, this beetle must take first place as the most destructive. It is the leader in the attack, while the others, 1 In all forests, and especially those in undisturbed or natural 'condition, a cer- tain percentage of trees seem to die naturally. While there is no such thing, per- haps, as a natural deathot a tree, there are those which, in their struggle for exist- ence with their many younger and more vigorous competitors, become weakened in their vita.ity and thus are more susceptible to the attack of their numerous enemies among insects and fungi, and also to the injurious effects of unfavorable climatic conditions, which, combined, cause them to die. Trees perishing in this manner, however, occur as isolated individuals, scattered throughout the forest, and seldom, if ever, in clumps. 16 found in the bark and wood, arc followers, allies, dependents, or natural enemies of one or more of tin* hark and wood miners. DESCRIPTION OF THE DESTROYER. This insect belongs t<> the order Coleoptera, the true beetles, which are most distinguished in a general way by their hard wing covers. Ii belongs to the family of beet Lee known as Seolyl idae and to i he genus Dendroctonus. dp to the present lime it has, together with several other distinct but closely allied forms, been recognized by entomolo- gists under the specific name ri/fi /it nn is, a name that was applied by the English entomologist, William Kirby, to a species described by him in L835 from specimens collected on a journey from New York state to the shores of Hudson Hay. It has been determined, however, by comparison with the original specimens now in the British Museum collections,- that the spruce-destroying beetle is quite distinct, and I have applied to it the name Dendroctonus piceaperda, meaning spruce destroyer. Tht ad ult (PI, II, figs. 1, 2) varies in length from three-sixteenths to five-sixteenths inch (4.7 to 5mm.), and in width from one-sixteenth to nearly two-sixteenths inch (1.1) to 2.6 mm.). It also varies in color from Light yellowish in the younger specimens to dark reddish-brown and. in some mature individuals, nearly black. It will be more readily recognized by the general observer from its common occurrence in the bark of dying and recently dead spruce trees; also by the character of its work, described and illustrated further on. Tht egg is a small pearly white object, scarcely to be distinguished, if at all, from those of other bark beetles of the same size. Tin larva is, upon hatching from the egg, a minute, white, legless grub (PI. II, tig. 4), which feeds on the inner bark and increases in size until it has attained a diameter equal to that of the adult ami a length somewhat greater. It maybe distinguished from any other similar larva as yet found in the Eastern spruce by a dark yellowish- brown space on the upper surface of each of the last two abdominal segments (PL II, fig. 4^). Thi pupa (PI. II, fig. 3) is nearly white, of the same size and some- what the same form as t he adult , but without free legs and wings, and is found in oblong cavities in the bark of the trees where the broods develop. 1 Detailed technical descriptions will appear in a special paper to be published later. BCimens of the Dendroctonus collected from spruce in Maine, together with specimens of another species from Hudson Bay and Lake Superior regions, were sent to the British Museum and were compared, by Mr. Charles O. Waterhouse, With Kirby "s types. He found that the one from Lake Superior agreed with the labeled specimen, the our from Hudson Bay agreed with another, and the speci- men* from Maine were different from any in the type series. 17 LIFE HISTORY OF THE BEETLE. The time of year when the investigation was made was especially favorable for studying the hibernating habits of this insect, and enabled the writer to commence a study of its life history with the later part to the close of its dormant or inactive period. HOW IT PASSES THE FALL, WINTER. AND SPRING. The fall, winter, and spring, and part of the first summer month are passed in all stages of the larva, from quite small to full grown, as well as in the adult stage, developed the preceding summer or fall. So far as could be determined by the writer, the eggs deposited too late in the fall to hatch before cold weather sets in. the pupae that develop too late to change to the adult, and some of the very young and tender adults, do not survive through the winter. The adults hibernate in the bark and usually but a short distance from where they were located when the}' transformed from the pupae or where the winter found them in their primary galleries. The larva? are found in their mines, where they ceased feeding in the fall. The very young to nearly matured larva? are often found in living- bark, while the developed broods of the adults are nearly always in bark which has recently died. In some trees many dead adults were found, which, owing to some unfavorable condition, probably within the bark itself, had died or been killed by the winter freezing, while in the greater number of infested trees all stages but the eggs and pup*, had not been injured in the least: indeed, they seemed to be in as perfect health as when they ceased activity in the fall. WHEN ACTIVITY COMMENCES IN THE SPRINO. When the first individuals were seen on May 28, near north latitude 45 . and at an altitude of about 2,000 feet, all of the hibernating stages were inactive. This condition continued until about June -i, when warmer weather set in and indications of activity were noted. On June 5, at Hammel's Camp, on the Little Magalloway, the matured larvae were found to be almost ready to change to the pupa?. The next day, in the same locality, numerous pupa? were observed, which had just transformed from the larval stage. From that day on to June 17 the pupa? were commonly met with and the young larva? were apparently feeding. Toward the 13th the adults showed evidence of uneasiness, as if preparing to emerge, and the first one of the season was observed excavating an entrance in the living bark of a healthy spruce. I was not positive, however, that it had not commenced this excavation last fall and remained in it over winter. Indeed none were observed flying then or up to the time the last observations were 3500— No. 28—01 2 18 made. just before my Leaving thai region on June 17. It is therefore possible that some individuals pass the dormant period in the outer hark, where they had commenced to excavate entrances in the fall. THE SUMMER PERIOD. Iii the course of Mr. Cary's observations in connection with the girdling experiments some important information relating to the Life history of tins beetle was noted by him. According to his notes the beetles eominenced to emerge about the middle of June. Galleries had been excavated in some of the girdled trees and eggs were depos- ited by June 1 !>. The first larvae were noticed on July 28 to 31. Pupae were eoniinou on September I, with a few recently developed beetles, and on October 4 many of the beetles had fully matured, but none had emerged. It is therefore probable that the beetles will not emerge and attack other trees before the following summer, although a few early developed beetles may emerge in October and enter the outer bark of living trees. Mr. Cary's observations furnish quite conclusive evidence that in northwestern Maine there is but one brood in a season, even from the hibernating adults, and that the period of development from the ey:g to the adult is about seventy to seventy-five days — from the middle of .1 une to the last of August. SUMMARY OF LIFE HISTORY. These observations would also indicate that activity ceases in the fall by about the middle of October, when all stages of the insect may occur in the bark of infested trees where they, with the probable exceptions of the eggs and pupse, remain until the first week in June. Activity then commences, the mature larvse change to pupa3, and by the middle of June those that pass the winter in the adult stage emerge and commence to excavate galleries and deposit eggs. The adults from the hibernating larv« of different stages, develop and continue to emerge possibly until the last of August. Therefore the eggs deposited by the late-developing beetles produce larva? which do not complete their development until July or August of the nexi year. Thus, the period of development may vary from about seventy daj^s to about twelve months, but all broods from eggs to matured and emerging adults remain in the bark about twelve months, of which they arc dormant about seven and one-half and active four and one- half. The following diagram will indicate the probable normal rate of development from the different hibernating stages: 19 EXPLANATION OF DIAGRAM. The accompanying di- agram (fig. 1) illustrates the dormant and active periods and the rate of development of Deit- droctonus piceaperda. The symbols at the left represent the different stages of the insect in the bark of infested trees when activity ceases, about the mid- dle of October: (•) rep- resents the mature, im- mature, and very young adults: (O) represents thepnpse; (° o O) rep- resent three stages of the larva-, and (•) the eggs. Commencing with the mature adults, in the upper line, the normal. or average, dormant and active periods, and the periods of development are represented as fol- lows: The dormant pe- riod of two hundred and thirty-two days ends about the 5th of June: in about ten days more the adults commence to emerge: in twenty days eggs are deposited: in thirty days larvae com- mence to appear : in sixty days the larvae are ma- tured: in sixty-five days pupa* commence to de- velop: and in eighty days from the time ac- tivity commences the first adults develop; they probably continue PSe^'S i 1 ? -? c r ? < '■ J I t ^ f $ <£ <£ . • h 4 ( ? ( p © < > < 1 4 2?- fi 2- r ■J> *^ *: ■c w; if S 2 r> , — & c-» a c *. V-S -. i St< n p 3 Cm — *" <■-. -a =1 ~ * ?S o, -. B p c*- «o; 9 a 1? < 5: i <~r. 2 k a !7 p § < - 5- a> -. 1 t; - ^ z 1 i 5J w> -b o® «» J o® • ► st H. O© • • 1 "* o 1 }© • < » • -d 8; oc •) • • • • 2 Cm s 3 • <&! fc • • c o« * # # " # . • o O.C r" * ;- • • • • • • c o OC P 5r £ # •• . • c o O OC l£ $r - ^ •.•o».ooo OOC )£ $ | .«oo»ooo OOOC I* 5 p f /% • • ooocooo 000(: *y # • • oooOcoo 000®(i •i $:> ► c^ ^ r/m • • o ooocoo®oo00©tf# //m • • o o o oooo®©o©®©t##i '/% • • o o OOOOO®00®0©####« ► S* I? ^/n |.^- ij° /% • • o o OOOOC®®®«Q®IHIM 1? Sotf- /%' . . o ooooOO®0®U®tMMM r n 5 3 cr m • . o o o 000®®®tMtNtttt1 Z + • • o o o OOOO®®®! ••••••••••< Ik ^ • • o coOOOO0®©O***+******C o o oooOO®®®0Mftftt«tt««t. S? • S P" 20 to develop until toward the last of September, but they remain in the bark until activity ceases. The hibernating, unmatured, and very young adults appear ten i<> twenty days Later than the fully matured ours; they continue t<> emerge and deposit eggs until about the lasi of July. The few pupa' present when activity ceases evidently perish by the Last of January, as do also the eggs. The three stages of hibernating Larvae develop to adults after activity commences in 1 1 1 < * same ratio as the hibernating adults, but owing to retarded development some of them probably do not attain the adult stage until Late in September. Thus adults would be com- ing out during the entire period of activity, which accounts for the^ existence of all stages when activity ceases in the fall. SPECIAL FEATURES OF THE BEETLE'S WORK. KINDS OF TREES ATTACKED. So far as known this beetle attacks only the spruce, and the most striking and important feature is its habit of attacking only the Larger trees. It is rarely found in trees below L0 inches in diameter breast-high, but in all infested areas is exceedingly common in those over IS inches at the same height. It also appears to have a decided preference for standing trees, although some evidence was found that it will breed in wind-felled trees and rarely in stumps and logs in cuttings. HOW AND WHEN THE ATTACK IS MADE. A study of the living trees which had recovered from a slight at lack, as well as those that were infested by different stages of the insect, indicated quite clearly that the first entrances are made in the bark of the healthy tree at a point from 6 to 10 feet from the base, and that trees which are weakened in vitality from disease or other causes may be attacked from near the base to near the first large branches. The fact that as a rule the infested trees are found in clumps or confined to definite areas of greater or less extent would indicate a social habit, and that the individuals may migrate in swarms from an old to a new locality and settle without any special choice except as to size or number of trees. Thus they invade the trees on all sides, and usually in such numbers as to prevent recovery from the first attack. As soon as the t rees commence to decline they are invaded by ol her bark-mining beetles and grubs, which aid in their final death and decay. ITS WORK IN AND BENEATB THE BARK. Tht i iiir