■S:/ir Circular No. 1 15. United States Departing BUREAU OF E L. O. HOWARD, Entomolog THE HORN Ffr Hi matobia serrata Rob.-Desv.) By C. L. Marlatt, M. S., Issistant Entomologist and Acting ChieJ in Absena of Chief . INTRODUCTION AM) SPREAD. The horn fly is one of the worst of the European biting Hies that attack cattle, but, curiously enough, it failed to reach this continent until a comparatively late date, notwithstanding abundant impor- tations of live stuck from Europe during nearly three centuries. It KIG. 1. ilxmatobia srrratu I larva; e, puparium; d, adult in resting position. Much enlarged. (From Riley and Howard.) was first discovered and reported to this Bureau in the fall of 1887 as occurring near Camden, N. .1. The following year it appeared in Maryland and Virginia, and thereafter, spread rather rapidly, and \>\ 1891 L892 it \\:i^ found over the continent front Canada to ¥qxas ■ 115— 10 and from Massachusetts to the Rocky Mountains. It has not heen reported as an especially injurious pest in California, but undoubtedly occurs there, and was carried with cattle from the western coast of the United States to Honolulu in 1897. The following year it had spread to all the islands of the Hawaiian group, and, under a favoring climate which permits multiplication to go on the 3 T ear round, it had become a perhaps worse pest on these islands in the middle of the Pacific than in the United States. The fust appearance of the fly in New Jersey and Pennsylvania makes it evident that it was brought to this country on European cattle in the early eighties. In the first publications on the subject it was stated that the fly was probably brought in through the port of Philadelphia in 1886, but the records of the Bureau of Animal Indus- try indicate that the importation of cattle through Philadelphia was discontinued early in 1885. From this fact either the fly was imported a year or more earlier than has hitherto been supposed, or else the fly must have come with cattle through some other port, probably New York. The former supposition, from the early records of distribution of the fly, seems the more likely. EARLY INVESTIGATIONS. The early records of the horn fly in 1887 and 1888 gave little indi- cation of its future importance to stockmen, but in 18S9 much ex- citement was aroused by the pest in New Jersey and throughout Maryland and in Virginia by the rapid spread of the fly and the excessive damage from it to cattle. This Bureau at once began a thorough investigation of the subject, largely conducted by Dr. L. O. Howard, assisted by the writer, and the life history and habits of the insect were worked out with fair thoroughness during this year. a In the same year it was being studied in New Jersey by Prof. J. B. Smith, 6 and during the years immediately following it was the subject of investigation and report by most of the official entomologists of this country and Canada. More recently it has beenstudied in Hawaii by D. L. Van Dine and Jacob Kotinsky, and the rearing of parasites and other natural enemies has been undertaken in Texas by agents of this Bureau for the benefit of and in cooperation with the Hawaiian authorities. The fly was early determined as the European cattle-biting fly named above, as the result of submitting material to eminent Dip- terologists of this country and abroad. The insect was originally described from southern France, and its rapid spread and greater "insect Life, Vol. II, pp. 93-103; Ann. Rep. Dept. Agr. for 1889, ]>p. 315-348. '< Bui. 62, N.J. Agr. Exp. Sta., L889 I fir. 115] damage in this countrj in its southward range would indicate t lint it is a southern European species. This fad maj account for the late date of its introduction to America, the chief importations of cattle coming from central or northern Europe. I (>\I\K>\ \ \\1 ES. The name "horn fly" was given ii at the very start, from its ha hit, especially early in the season, of settling in large numbers around the base of the horns, and it i- imu everywhere known by this name. For the first few year-, when the fact of it- being a new pest was not fully appreciated, various name- were given it, some of which applied to other biting gnats, such as "buffalo fly," "buffalo gnat," and "Texas horn fly." The name "horn fly" is so appropriate that the others were short-lived, hut this name carries a slight chance of misunderstanding, inasmuch a- the insect does not affect the horn, but simply chooses this point a- a resting place when it is inactive — largely because the base and inner curve of the horn is a point which the animal can not reach, either 1>\ swinging the head from side to side or with the tail, to dislodge the Hie-. Tin; DAMAGE OCCASIONED BY THE HORN 111 The horn fly i- a blood-sucking insect, hut the damage occasioned by it is chiefly the result of the irritation to cattle which prevents proper feeding and normal assimilation of food, and hence loss of flesh di' lessened milk production. There is also the actual loss of blood, which may he considerable when these Hie- are abundant. The injury by the fly in New Jersey, Maryland, and Virginia during the first year after it- introduction was very considerable, and this is true of its first appearance in the wider and wider areas covered by it. After a year or two, however, the cattle perhaps became more used t<> it, and the natural enemies of other Diptera. beginning to attack it. reduced its nunihers to some extent, so that the loss from it was, as a rule, much lessened. Particularly in the West and Southwest, however, the damage from the horn fly continues to be of very serious moment. Dining the first year- of the horn fly, when it was a new and little understood menace to cattle, the losses occasioned by it were undoubtedly much exaggerated. Nevertheless the I..--. when the fly is abundant, is still very considerable, showing in reduced vitality, lack of growth, or lessened yield of milk, the production of milk often being cut down from one-fourth to one-half. In Canada the late Dr. dame- Fletcher estimated the loss, in Ontario and Quebec, at one-half of the product of meat and milk. I fir. 1 15] The horn fly exhibits a certain preference for red or other dark- colored cattle, and that such animals are more thickly infested has been frequently noted. When the insects are abundant, however, this preference is not so strongly marked. Occasionally sores are formed on the animals, which in the South and West may become infested with the screw worm (Chrysomyia macellaria Fab.). These wounds or sores are, as a rule, only indirectly the result of horn-fly attacks, but are commonly produced by the rubbing of the cattle in efforts to allay the irritation from the bites. The loss occasioned by the horn fly to other animals is, as a rule, inconsiderable. Sometimes horses are attacked, and especially cow ponies, and injury to sheep, as pointed out by Norgaard," is compli- cated with sheep scab. LIFE HISTORY AND HABITS. The appearance and abundance of the flies is governed by tem- perature and rainfall. In the latitude of Washington they are first noticed in May, and become most abundant in July, gradually dwindling to November or until sharp, frosty nights become frequent. Farther south they appear earlier and remain in evidence later. The study of this insect in Texas by agents of this Bureau, notably Mr. J. D. Mitchell, at Victoria, indicates that the fly reaches its first maxi- mum of abundance in May. During the subsequent dry period the fly decreases in numbers until fall rains begin, when a second maxi- mum is reached in late September, which is checked by the frosts of the latter part of October. Continuing on from then until March the fly is kept down to comparatively small numbers by low tempera- tures. The reduction of the numbers of the fly in Texas by a dry, hot summer is sometimes as great as 95 per cent from the maximum of May. The characteristic habit of the fly in clustering about the base of the horn is developed only when the flies are abundant. When they average only 100 or so to an animal, comparatively few will be found on the horns. The horn-clustering habit is more noticeable in the spring and early summer than in autumn. The horns are not the only resting places, and many of the flies cluster upon the back, be- tween the head and the fore shoulders, where they can be reached by neither head nor tail. When the cattle are feeding, the flies are found over the back and flank and on the legs, and during a rain- storm they flock beneath the belly. When the animal is lying down, a favorite place of attack seems to be under the thigh and back belly around the udder. The characteristic appearance of the flies on the horn is indicated in the accompanying illustration (fig. 2). a Rep. Agr. and Forestry, Hawaii, 1905, pp. 171, 211, 212. [Cir. 115] In the Feeding position the wings arc slightly elevated, and arc held out from the I >< >< 1 \ al an angle of 60° from the abdomen; the legs arc held oul widely, and the beak, inserted beneath the -kin of the animal, is directed almost perpendicularly (see fig. •"». c). Before inserting its beak the |1\ works it-, way through the hair close to the skin, hut is able at the leasl sign of danger to rise instantly in (light, to return as quickly. The characteristic appearance of the fly is 3hown in the accompanying illustration (fig. I). It is about half the size of the house fly, which it closely resembles, hut is much less robust. Differing from other biting flies, the horn fly normally stays on the cuttle night and day, and when not feeding rests on the cattle as already described. in.. 2. — Cow-horn showing band of resting horn Hies. Reduced. (From Riley and Howard.) I'he egg-laying habit of the insect was not easily discovered and is somewhat peculiar. The eggs are laid singly and usually upon their sides upon the surface of wet dung. The moment the latter is dropped, a swarm of flies dart from the animal to the dung and re- main there a few seconds, or a minute at the most, during which time many eggs are deposited. Egg laying is chiefly during day- light, between 9 a. m. and 1 p. m., and most abundant during the wanner morning hours. So far as we know, they are laid upon no other substance, and never upon old dung. The larva 1 upon hatching descend into the dung, remaining, how- ever, rather near tin 1 surface. When full grown they are about two- lift lis of an inch in Length and of the normal color and form of the related dung maggots. The puparium is formed in the ground be- neat h the dung. The time elapsing from tin 1 egg to the adult is from ten to seventeen days, and there are probably seven or eight genera- tions annually in t he latitude of Washington, with more in the South; [Cir. 115 1 and continuous breeding in a tropical region like the Hawaiian Islands. The winter habits as studied near Washington, D. ('., indicate that hibernation normally takes place either in the adult stage or as puparia below the surface of the ground. PARASITES AND NATURAL ENEMIES. The natural enemies of the horn fly, like those of most other dung- breeding flies, are destructive to the insect in its larval and pupal stages. Therefore the bringing over of the insect from Europe in the adult stage with cattle resulted necessarily in its freedom for a time from the control by such natural enemies. The similar enemies of other dung flies in this country, however, undoubtedly very soon began to exercise a certain degree of control, and this may account Fig. 3. — Horn fly: a, Head of female, front view; b, head of male, front ■v icw . c, head from side enlarged. (From Riley and Howard.) (ireatlv somewhat, at least, for the much' greater damage occasioned by the horn fly in the first years of its occurrence in the different zones of its spread across the continent than was the case during subsequent years. Very early after the appearance of the horn fly it was noted by Mr. F. M. Webster that in Ohio fully 20 per cent of the flies were infested by one of the scarlet mite fly parasites (Gamasida*). This mite was not determined, but was probably one of the native species commonly seen on other flies. The introduction of the horn fly into the Hawaiian Islands and the heavy losses there occasioned by it led to an active investigation on the part of the island authorities of parasites and predaceous enemies. Mr. Albert Koebele imported, in 1905, from New South Wales, quan- l it ies of material from which dung beetles were reared and introduced into the islands. In 1906 Mr. Koebele came to the United States and made extensive collections of material in California and Arizona, and from this material at least six or seven .species of dung beetles were introduced into the Hawaiian Islands, and two species of true parasites. [Cir. 115] The beetles in question are those which habitually live in cattle dung and feed upon living maggots therein, or are of the tumblebug variety which disintegrate the dung shortly after deposition, thus preventing or checking the breeding of the flies. The true parasites reared from material sent by Mr. Coebele from Arizona proved to be Eucolia impatiens Say, styled "the Arizona dung-fly parasite," and a species of Eutrias, styled "the lesser dung- fly parasite." These two minute four-winged flies are undoubtedlj normally enemies of native dung-breeding Hies, but take readily to the horn fly. They were reared in considerable numbers and dis- tributed among the ranchmen on the islands. It is too early yel to determine whether these importations will he of much practical value in controlling the horn fly. 'Two other similar minute Hymenopterous parasites, belonging to the genus Spalangia, were reared by Mr. Kotinsky from pupse of the common stable fly (> * ((licit vans L.), from material collected on the [sland of Hawaii. One of these, Spalangia hirta Haliday, confined with horn-fly pupse, promptly attacked the latter, and in three or four w eeks a brood of these parasites \\ as successfully reared. Later, horn-fly pupa* collected in the held were found parasitized by this species. The other parasite, S. lanaiensis Ashm., supposed to he a native species, was also again reared from Dipterous pupa 1 . That both of these, will become important enemies of the horn fly seems to be established. MEANS Ol (ONI KOI.. The simple means of prevention of abundance of the Hies by the destruction of larvae in the dung and the protection of animals from the attacks of the adults, suggested in the earlier investigation of the subject by thisBureau, have remained thestandard means of control, with some improvements and amplification enabling them to be carried out on a larger scale and at less cost. There are two principal methods of control one. the destruction of the larvSB and pupa- in the cattle dung by direct measures or by the act ion of nat ural enemies already discussed; and the other, the protection of cattle either by the use of repellent ointments or by the actual capture and destruc- tion of the adult flies. Repellents. Almost anj greasj substance will keep the flies away for from a few hours to several days. A greal many oils and fats have I n experimented with, and the commercial product known as li-.h or train nil. flrst suggested, remains the best easily available oint iiieni. The protection by the use of tin- mixture varies in different regions. En the dry, hot area of the West and Southwest protection lasts only two or three days; in the more moist and cooler regions of the ii:.] 8 East and North, five or six days. This oil costs from 50 to 7o cents a gallon. The addition of a little sulphur or carbolic acid is of benefit, the latter making the application somewhat healing if any sons have been formed. Where only a few animals are to be treated, as a home supply of dairy cattle or a dairy herd, the application can be made with a common painter's brush. It may be unnecessary to attempt to protect the entire animal, but only those parts not reached by the head or tail, although the more completely the animal is covered the greater will be the reduction of loss. In Virginia Prof. W. B. Alwood found that animals could be treated with the standard insecticide, kerosene emulsion, applied with a small hand-spray pump. This application killed all the flies that were actually wetted by it and gave protection to the treated animals for two daj^s. With a little tobacco water added he found two appli- cations a week sufficient, using from 1 to 2 pints for each animal. The application was made just after milking, and was only tested on dairy animals. Kerosene emulsion is prepared after the following formula. The crude oil yields a stronger and more lasting product : Petroleum, refined or crude gallons. . 2 Whale-oil soap (or 1 quart soft soap) pound . . J Water (soft) gallon. . 1 The soap, first finely divided, is dissolved in the water by boiling and immediately added boiling hot, away from the fire, to the oil. The whole mixture is then agitated violently while hot by being pumped back upon itself with a force pump and direct discharge nozzle throw- ing a strong stream, preferably one-eighth inch in diameter. After from three to five minutes' pumping the emulsion should be perfect, and the mixture will have increased from one-third to one-half in bulk and assumed the consistency of cream. Well made, the emulsion will keep indefinitely and should be diluted only as wanted for use. In limestone regions, or where the water is very hard, some of the soap will combine with the lime or magnesia in the water, and more or less of the oil will be freed, especially when the emulsion is diluted. Before use, such water should be broken with lye, or rain water should be employed. It may be used pure or diluted with one part of water for local applications with a brush, or with two or three parts of water as a spray. A mixture recommended by the Kansas Experiment Station," claimed to be as satisfactory and considerably cheaper than fish oil, is made after the following formula: Pulverized resin, 2 parts, by "Press Bui. No. ti">. March 20, 1900. [Clr. l 15] measure; soap shavings, I part; water, J pan; fish oil, l part; oil of tar, 1 part: kerosene, 1 pari; water, 3 parts. Place the resin, snap shavings, J pan of water and fish oil together in a receptacle and boil till the resin is dissolved. Then add 3 pans of water, follow- ing with the oil of tar mixed with the kerosene. Stir the mixture well and allow it to boil for fifteen minutes. When cool the mixture is ready for use, and should be si irred frequently while being applied. This mixture costs about 30 cents a gallon, and from one-eighth to one-half pint is sulhcient for one application with the brush method. The methods jus! described are not applicable to large grazing herds or cattle on the range. Fly control on iht range. For the control of the hom fly on range cattle on a large scale the dipping- - * ats system employed for the con- trol of the cattle tick or other skin parasites offers the best solution of the problem. The oily dips used for the Texas-fever tick, described in a publication of the Bureau of Animal [ndust ry of tins Depart men t " can he made to serve as a very effective means of controlling the horn fly. It was early discovered thai dipping cattle in these oily mix- tures in the ordinary way was of little service in destroying the horn Hies. The cattle dips were repellent to the horn fly lor a very short period, and the percentage of the Hies killed by the operation was inconsiderable. During the last three years, however, Mr. .1. I>. Mitchell, an agent of this Bureau, working with Mr. \Y. I). Hunter in Texa>. has. in a study of the requirements for horn-fly control, found that by a very simple modification of the ordinary dipping vat a very large percentage of the flies on the cattle can he desl roj ed, with the consequent very notable limiting of the loss from this fly pest. With the vats as ordinarily constructed, most of the Hies aban- don the animal at the moment it plunges into the dip and escape, and go to other animals, and ultimately with t he drying of the dipped animal return to it. Mr. Mitchell found, however, that 1>\ putting a splashboard near the top of the vat on either side, about 4 feet above the level of the dip, the water thrown up violently as the animal plunges m is caught by these splashboards and is tin-own hack as a spray, filling the airspace above the animal and drenching and destroying the Hies in their effort to escape. The few of the horn flies that may escape, together with those which abandoned the animal at the entrance to the vat. were observed to hover or settle on the chute fence, and many would alight on the next animal coming along. I Ie also found t hat w here t he animals have been heated in corralling and getting them into the chute the I lies .stick much closer and are much less apt to take quick flight, thus insuring the capture of a larger percentage of them by the dip and spray. rmers' Bulletin 378. < Ictober I K)9 I (Mr. 11.-.] 10 The first suggestion of splashboards was not as a means of con- trolling the horn fly but to keep the fluid from wasting over the sides of the vat and to protect the men who were w T orking near the vat. When a large animal strikes the fluid the splash will fly as high as 6 feet, and the spray will scatter widely. The accompanying detailed sketches illustrate two vats equipped with splashboards which have been used very successfully for a num- ber of years in Texas. The first sketch (fig. 4) is a cross section of the vat constructed by Mr. J. J. Welder, Victoria County, Tex. A ground plan of the entrance is illustrated in figure 5. Mr. Welder's vat is a rather large one, having a surface level of the dip 5 feet wide but w T ith an entrance chute to the vat of only 3 feet and 9 inches. The splash- boards are 2 feet wide and 20 feet long, ex- tending from the termi- nation of the entrance chute. In the case of this dipping vat the ani- mal is confined to the middle of the vat and entirely away from the splashboards b} 7 the nar- row entrance chute. Another similar vat is illustrated in figure 6. This vat w T as con- structed by Mr. A. P. Borden on the Pierce Ranch,Wharton County , Tex. The splashboards are 1 foot wide and ex- tend the full length of the vat, andean be used, if necessary, as a walk in assisting cattle in trouble. The ends of the splashboards next to the entrance arc rounded off in the case of this vat; but the entrance slides, as illus- trated in the ground plan of the Welder vat (fig. 5), and the height of (he splashboards above the dip level, have in the actual treating of hundreds of cattle prevented any difficulty of catching or colliding of the animals with the splashboards, and were used on a number of \ als in Texas most successfully during the years 1907 to 1909. [Cir. 115] -Cross section of dipping vat used by Mr. J.. T. Welder. (Original). 11 EE ta» 3 IB With vats equipped like the above, from 75 to 80 per cent of the horn flics mi the cattle are destroyed." Mr. Hunter experimented with a small model of a dipping vat, and 1'ou in I that if the splash were received on a slightly curved galvanized iron sheet instead of a hoard it was considerably more effective in dis- tributing the hack throw of the \\ ater in the form of an efficienl spray. The arsenical dips used for the cattle tick would have comparative!} little value for the horn fly except thai very likely a good many flies might he caughl and destroyed bj merely being wetted with the dip. A similar treat incut has recentl} been the subject of experiment in the West . An apparatus has been con structed, designed in r e part icularly for the destruction Of skin parasites of cattle, to supplant the old method of dipping in a vat. It has been suggested that this apparat us will furnish a ver\ good means of con trol in the case of the horn fly. The probabilities are. however, from the experience with the horn-fly traps re- ferred to below, that most of the flies would abandon t he cat t le at the moment of entrance to the cylinder, and its efficiency as a means of horn-fly control i^ very problematical. The process consists in driving the animals t hrough a large cylinder through the sides of which a powerful gasoline pump causes sprays of the insecticide to strike the animals from all quarters and thor- oughly wet them. This machine is patented and is sold at a rather excessive price. The liquid used i> an emulsion of crude petroleum l or further details of the construction of dipping va 1 urmers' Bulletin 378, "Methods "i" Exterminating the Texas Cattle Tick," by II. W. Graybill, Bur Animal Industry In the case of the val there described, in successfully use the splashboard ii may be necessary i" increase the height of il the vat so that i lie splashboards can lie placed i feet or a little more above the level of the dip ii:,] JilJJkniIIDi Km..: Ground plan of dipping vat used by Mr. J. J. Welder. IE (Original.) 12 in water in the proportion of 20 gallons of oil to 80 gallons of water, with the addition of 5 pounds of soap. This apparatus is claimed to be able to take care of from 3,000 to 4,000 head of cattle per day. With this or some similar device the control of the horn fly ou a broader scale may prove practicable. Horn-fly traps.- — Various attempts have been made to collect horn flies from cattle by means of traps, the general plan being to pass the Fig. 6.— Cross section of dipping vat used by Mr. A. P. Borden. (Original.) cattle through a dark room or chamber arranged with brushes at the exit to drive the flies from the cattle and retain them in the chamber, where they may be attracted to a lighted cupola, captured, and destroyed. Mr. P. J. Parrot t, while connected with the Kansas Experiment Station, conducted elaborate experiments in this direc- rCir. 1151 i:: tion." hut the results were most unsatisfactory, the great majority of the flies abandoning the cattle al the moment of entrance, so thai onlj about •"> per cent of the flies were captured. Destruction of larva and pupx. The destruction of larva' and pupae in the dung by direct measures and consequent reduction in the numbers of the adult insects is a possible means of control, not, however, always practicable, and having little utility in the case of range animals. Two methods of locally destroying the Hies in the dung have been shown to be fairly effective. A spadeful of lime thrown on com dung will destroy the larvae living in it, and in small past ures such treat mi 'nt of dung, especially at points where the cattle arc more apl to congregate, may be feasible. Tins treatment is espe- cially useful if carried out during May and dune, as every larva killed of the early broods means a very large reduction in the number of flies for midsummer and later in the season. Prof. J. B. Smith suggests another means of control, namely, the spreading out of the fresh dung with a shovel, w Inch causes the rapid drying of the dung and the destruction of the Dipterous larvae con- tained in it. This method also is feasible only in the case of small pastures and in dry weather. An inexpensive method, suggested h\ Mr. D. L. Van Dine, of scattering the dung in yards and pens and causing it to dry quickly is to allow a number of pigs to run with the cattle. In their efforts to obtain undigested particles of food the pigs will ell'cctualU destroy the dung as breeding places for the fly, at least during dry periods. A dairyman in Texas, as reported by Mr. J hint or. has followed an analogous method of control which has given him very considerable protection from the horn fly. He makes it a practice to collect daily the dung in and near the dairy barns, and every few days this collected materia] is taken out and distributed with a spreading machine on t he past ure, so thai it promptly dries up and the breeding of larva' in it i^ prevented. Wherever this practice i- feasible it is to be strongly recommended, and has the important additional argu- ment in its favor of conserving the valuable manurial materia] which might otherwise very much reduced in numbers by the rapid desiccation of the cow droppintrs. Approved : James Wilson, tary of Agricvll Washington, 1> C November 17, 1909. a Kansas State Agr. Coll. Exp Sta Pre Bui. No. 19, November 7, 1899. ( Clr. it.".] o UNIVERSITY OF FLORIDA 3 1262 09216 5124