Historic, archived document Do not assume content reflects current scientific knowledge, policies, or practices. UNITED STATES DEPARTMENT OF AGRICULTURE Washington, D. C. February, 1926 HOST RELATIONS OF COMPSILURA CONCINNATA MEIGEN, AN IMPORTANT TACHINID PARASITE OF THE GIPSY MOTH AND THE BROWN-TAIL MOTH | By R. T. WEBBER, Assistant Hntomologist, and J. V. SCHAFFNER, Jr., Principal _ Scientific Aid, Gipsy Moth and Brown-Tail Moth Investigations, Bureau of Entomology 1 CONTENTS Page Page Source of collections and data_---_-. 2 | Status of summer hosts_._____-___= Care of collections and methods of Records of Compsilura rearings other Rearing kee ee 4 than those recorded at the Gipsy Life history and hibernating hosts__ 4 Moth Laboratory__---____-~__~_ 27 Status of hibernating hosts of Comp- Effect upon native parasites_______ 27 Sire ee see 5 | Effect upon host species___________ 30 Generations of Compsilura______-__ “ueuitenature Ge 118 184 828 8 20 18 19 856 Ennomos subsignarius Hiibner---_.-- 1, 200 865 | 403 853 257 0] 3,080: Epargyreus tityrus Fabricius__-.----- 0 21 0 0 0 66 62 226 374 1 Numbers in italic indicate that Compsilura was reared. HOST RELATIONS OF COMPSILURA CONCINNATA 3 TABLE 1.—List of host insects of Compsilura concinnata Meig. received at the gipsy moth laboratory, Melrose Highlands, Mass., from 1915 to 1922, in- clusive—Continued 1915 1916 1917 1918 1919 1920 1921 1922 | Total Epicnaptera americana Harris-____-_- 0 4 6 9 4 3 3 4 33 Estigmene acraea Drury-__----.------- 25 208 696 185 619 105 106 114 | 2,058 Euchaetias egle Drury____-----_--_--- 0 152 675 845 497 72 166 779 | 2,675 Eugonia j-album Boisduval and ZO COMP Eee Nee SELENE Se Pg 16 43 2 13 0 0 0 0 74 UG OCUISTCHTPVS OLEINOC Bs IIR TAG) 2 sees wes pa tema | eT AY SEL aed ca | Es | ae ao De Euthisanotia grata Fabricius_~___--_- 0 0 8 0 3 0 0 ll Euvanessa antiopa Linné______._____- 250 651 418 | 2, 248 667 430 | 1,124 | 1,076 | 6,758 Evergestis straminalis Htibner__.___-- 20 14 11 2 0 48 0 100 Halisidota caryae Harris_________-___- 0 367 | 1,647 47 250 4 4 22 | 2,341 Halisidota tessellaris Smith and INYO) 9X0 FSIS NANA RS AU at 0 229 | 1,572 255 26 34 12 161 | 2,289 Hemaris thysbe Fabricius _-...__.__-_- 0 0 0 0 0 77 22 6 105 Hemerocampa leucostigma Smith and PANTO eras toe aeee hee as NMRA 0 99 222 480 60 781 548 | 1,987 | 4,122 Hemileuca maia Drury_____....__._-- 685 195 984 | 8,059 | 2,730 780 | 2,004 956 | 11, 342 Heterocampa guttivitta Walker______- 0 33 3 276 | 1,749 842 | 0| 2,876 Heterocampa umbrata Walker_______- 0 0 0 0 10 0 0 0 10 Hydria undulata Linné________.___-_- 0 0 71 87 | 1,161 817 419 660 | 3,115 Hyphantria cunea Drury 3___-_.______ 0 836 | 1,373 | 1,671 | 7,577 | 8,623 | 2,940 | 2,478 | 25, 498 Lycia cognataria Guenée__________.__- 0 0 0 28 3 86 9 81 Malacosoma americana Fabricius 4____| 8,650 | 2,099 | 1,156 810 |13, 574 |10, 832 | 4, 850 966 | 42, 937 Malacosoma disstria Htibner_-________ 2, 520 278 57 207 302 348 679 688 | 5,079 Mamestra adjuncta Boisduval_____-__- 0 11 6 5 1 4 0 4 31 Mamestra legitima Grote____________- 0 2 6 § 3 3 2 2 23 Mamestra picta Grote____.._________- 206 584 840 9 291 166 118 18 | 1,682 Melalopha inclusa Hitbner__________- 0 0 0 50 261 456 257 45 | 1,069 Nadata gibbosa Smith and Abbot-.._- 0 2 3 0 8 7 0 12 32 Notolophus antiqua Linné ___________ 8 6 99 21 8 0 7 106 249 Olene basiflava Packard §.._________.. 10 | 2, 643 399 12 153 0 90 3 | 3,210 Mleners peu Woe SA eR RN ey ELS ae 0 0 0 1 0 0 0 0 1 Paonias myops Smith and Abbot-_-_-_-- 0 2 0 20 0 59 5 19 105 Papilio polyxenes Fabricius__________- 35 49 179 8 71 20 62 42 466 Papilio troilus Linné____________2__- 0 0 2 0 0 78 72 53 205 Papilio turnus Linné________________- 2 2 i 3 3 58 18 8 96 Pheosia rimosa Packard__...____-___- 0 0 0 it 0 16 5 1 23 Phigalia titea Cramer___._._.____-___- 896 527 54 8 3 6 1 15 | 1,010 Phlegethontius quinquemaculata Ha- W/O) GL a ee He PE Ve ta We ea ity ey ae 3 &9 79 1 202 109 6 37 526 Pholus achemon Drury_.___-__----_-- 0 0 0 0 0 1 0 0 1 Plathypena scabra Fabricius. ________ 0 0 0 0 237 1 1 0 239 lusiodontacompressipalpis/Gueneess saan eee ean eee eke SES a Ss ee ee Polygonia comma Harris__.__.___.__-_- 1 0 0 0 0 0 0 0 1 Polygonia interrogationis Fabricius -- 0 6 0 79 266 10 a 368 Pontia rapae Linné 6_____...._-_______ 0 174 | 1,139 256 | 1,284 | 1,368 | 1,030 222 | 5,423 Rorchetria: dis parjpletmm 6128 spe Nene ON eG aay Re Utes Cea 5k eileen ge! ays d ec a ai [aa oie Pteronidea ribesi Scopoli_______.-___- 300 500 524 162 | 1,980 552 521 | 1,684 | 6,123 Pyrophila pyramidoides Guenée. ____- 0 24 3 5 8 9 0 10 59 Rhodophoray florida; GuemGerw eyes aes ee i eee Ie Ne ee Samia cecropia Linné_________________ 4 7 31 7 8 3 12 74 Schizura concinna Smith and Abbot__- 85 449 | 8,478 | 2,074 | 8,608 | 1,995 498 187 | 12,364 Schizura unicornis Smith and Abbot-- 0 3 cial 4 1 4 4 9 26 Scoliopteryx libatrix Linné__._______- 0 0 0 0 2 3 0 7 12 Sphecodina abbotii Swainson________- 0 13 13 9 13 14 10 12 84 Slo OTe ar vae een se ee e 0 0 0 0 0 1 0 0 1 Sphinx gordius Stoll_________________. 0 1 1 0 4 19 3 6 34 Stilpnotia salicis Linné 7_____________- 0 0 0 0 0 627 0 0 627 BIPVATIAOSISP hie sce 5 se Ua eT 0 0 0 0 0 83 66 3 141 Telea polyphemus Cramer-_..____----- 12 3 18, 8 2 2 3 2 45 enthredinidlarycs Sa. 2 0 150 | 216 25 153 805 47 181 | 1,576 Tenthredinid larvee 9_____________-__- 0 0 0 0 0 0 86 0 86 Vanessa atalanta Linné________._____- 26 0 9 266 683 143 5 88 | 1, 219 Vanessa huntera Fabricius__..-__.___- 0 1 0 i 18 25 3 7 55 15, 619 |12, 601 |21, 118 |18, 630 |44, 382 |34, 168 |21, 894 |19, 377 |187, 789 2 Collections of E. chrysorrhoea and P. dispar are not included in this table. ® These collections, number- ing several thousand larve, are made each year for various purposes and are handled by the laboratory force. 3 Nearly 6,000 larve of H. cunea were received in 1921 and 9,000 in 1922, but the writers were unable to handle more than the number listed. 4 Nearly 25,000 larve of this species were received in 1921 and 20,000 in 1922, but the writers were unable to handle more than those listed. 5 Collections of O. basiflava include the hibernating larve of which 90 per cent died from unknown causes. 6 Large collections of P. rapae were received at the laboratory during 1914 and 1915 but were used by Cul- ver (2) in his life-history experiments. 7 Collections received during 1922 and 1923 were handled by the laboratory for ce. ® Neurotoma fasciata Norton. 9 Pteronidea coryla Cresson. 4 BULLETIN 1363, U. S. DEPARTMENT OF AGRICULTURE The territory from which the collections were received is repre- sentative of the gipsy-moth area of New England, the bulk of the material, however, being from those sections about Melrose High- lands, Mass.; Bangor, Me.; Claremont, N. H.; Westerly, R. I., and Putnam, Conn. There are also collections (not included in the above summary) from the gipsy-moth territory in New Jersey. In this area there had been prior to 1921 no systematic introduction of parasites and the material obtained answers well for check purposes. These collections are represented by over 125 species aggregating at least 10,000 larvee. CARE OF COLLECTIONS AND METHODS OF REARING Ordinary mailing tubes, 2 inches in diameter and 7 inches long, with screw tops, are used with great success for the shipment of material from the field. On receipt of the collections at the labora- tory the contents are sorted, identified if possible, and placed in receptacles for rearing. Various methods are used in handling the collections. In the case of known insects the task is easy since many species can be success- fully reared in pasteboard boxes or in covered trays. The frame- work of these trays is of wood, measuring 12 by 12 by 5 inches; the bottom is covered with cloth and can readily be replaced when necessary. All trays-are furnished with tightly fitting glass covers which slip into a grooved top. Where there is any doubt as to how the species may best be reared, glass jars, supplied with earth, are used. Hibernating larve and species which pass the winter as pupe or prepupe are difficult to handle successfully. In caring for the hi- bernating larve the best results were obtained from the use of Riley cages. For pupal hibernation, glass jars, galvanized-iron cylinders with bottoms of fine mesh wire screening, and wooden boxes of various sizes are used. ‘These are partially filled with earth and the larve allowed to transform at will. The glass jars are either re- tained in the outside rearing cage or brought into the cellar of the laboratory, where they are not subject to extreme temperatures. The cylinders and boxes which have been successfully used are set in the earth as soon as the larve pupate, and covered with straw. Practically the same methods are used in caring for the tachinid and. hymenopterous parasites. LIFE HISTORY AND HIBERNATING HOSTS Briefly, the life history of Compsilura concinnaia is as follows: During the spring the last-stage larve issue from their hibernating | hosts and pupate close by. Ten days or so later the adults appear. | In New England there are two or more generations upon alternate hosts, the progeny of the last generation hibernating as larvee within certain lepidopterous pupe. Spring emergence of the overwintering generation is variable, depending upon climatic conditions (Table © 2). During 1921 a few flies issued in April, whereas the material — collected in 1916 gave no results in 1917 until June 11 and later. © Most of the rearing records, however, which have been conducted HOST RELATIONS OF COMPSILURA CONCINNATA 5 under natural conditions show a much earlier date of emergence. In the field, collections of adults range from May 1 to November 1. TABLE 2.—Showing the emergence of hibernating flies from their host pupe (natural environment)? Date of individual emergence Host Period of emergence TING Sel Os Noemie ee EE SGT Deilephila gallii Rottemburg_______..._________- ARTO Sere eee UN at pte Diacrisia virginica Fabricius____......__.._.___- June 3-12. MUTI Gee V2) ct eke he A OR eri Callosamia promethea Drury--_-_-.-._____.-_-__- 1917 ATW aC) 118 ba pe Tae IEA CaP tdi ae WUT Arsilonche albovenosa Goeze__.._-...-.-_-..___-- 1 ET) eee ee ge a ae ee Apatela brumosa Guenée: 2 S218 0.2. eek le June 11-15 "TUS ey UE a ND Be MnatelastunciteralGuencel sonnet Wer esis Snes Men pss tee wet ENS Tih CP Papilio polyxenes Fabricius..____....._.._.____- 1918 ae an Van) 2427 See eye GEOR UY iacrisia virginica Fabricius._.._._........_____- \ mS AU UTT NOY Cte bse eee a ene tbe es RO Lo Schizura concinna Smith and Abbot_-._.__.__-- May 24-June 6. 1919 |) ENGR AD gy Ria Re Ca A LOIN gc Apatela furcifera Guenée_______..-_-__________-- TRUER TYAS 83 ae Ne cea LN ee de Hyphantria cunea Drury-_-_-_......-------_.----| PVT AD Pa oR cra Mice Ok ay eee Apatela brumosa Guenée__..____--__-_----_-_____- | May 28-31, June 10._.._.__.___-__- Euchaetias egle Drury. .-...-.-_--2-- 2-2-2 2. May 27-June 10. Play 2828282 Ld Vl. ee eee eee | Arsilonche albovenosa Goeze___..-_-----------2- Nai 29 Sears es ed ac Pontiarrapae hinn6. 2 2s ek ee ANGERS BASES i Top a ee iPheosiawimosa Packarde.22) 222. ete ey 1921 Moke MMERDEC 2-202 0. Sure Ue ast Papilio polyxenes Fabricius___.....---.._-_-__-- PANT Ts Aes MIE NRE RY SR Th Hyphantria cunea Drury_-_-__------------_---__- play AeA Es sleet oe MI at Mui Noh 2 ad Feones zayops Smith and Abbot.--_-..___-__-- | AONE Gt 24 ee det oie eek a ena ontiarapaewuinnes 22 eo re eee | May pia aera MEUM RSAC es acne stp a aa eed Arsilonche albovenosa Goeze___..._-_-_----___-- Apr. 12-May 28. Haye 21 255 28008 ae Bes ye EN Apatela furcifera Guenée_______._._-_-_________- | ay; 2S LONE Oa Apatela americana Harris___........_._-___-__-- | MeN 28-24 yo ob eee ee Estigmene acraea Drury-_-.......---_----------- 1922 gS LES GSS OU SSRI I ve a Estigmene acraea Drury._.._._.--___--.------.. May, 21—June 1022 9222 ee Euchaetias egle Drury._.....-.--_.-.----_------ May 1-June 10. IMA Los Soca: wean Sa ee eS. PRA AN AOS }SP Gye see ye ON NETS a Cer) eS 1 No hibernating records for 1920 were obtained. There are other records of Compsilura being reared from over- ‘wintering pup of Diacrisia virginica, Callosamia promethea, Mamestra picta, Mamestra legitima, Ampelophaga myron, Papilio troilus, Sphine gordius, Paonias myops, Apatela americana, and Deidamia inscriptum, but since these are all laboratory records, the rearings having taken place under artificial conditions, no mention is made of them in the table. Schizura unicornis, which overwin- ters as a prepupa, has also given Compsilura under laboratory con- ‘ditions. Among the hosts recorded by Culver (2, p. 5) are two spe- cies, Plusiodonta compressipalpis and a geometrid; the record of the ‘former was dated April 7, 1918. Smith (8) records a rearing of ‘Callosamia promethea, the parasite issuing May 2, 1914. At West ‘Springfield, Mass., in 1915, the same writer succeeded in recovering ‘Compsilura from the overwintering pupa of Diacrisia virginica, ‘two flies issuing May 12 to 15, 1916. The conditions under which ‘the rearing took place are not known. STATUS OF HIBERNATING HOSTS OF COMPSILURA } __ The abundance of Compsilura in the spring and consequently the ‘degree of parasitism upon the brown-tail and gipsy moths are to 6 BULLETIN 1363, U. S. DEPARTMENT OF AGRICULTURE a great extent due to the abundance of its hibernating hosts.2 With two exceptions (Schzzura concinna and S. unicornis), these host in- sects pass the winter in the pupal stage either above or below the surface of the earth. The majority of the species are solitary, although a few are gregarious, such as Hyphantria cunea, E'uchae- tras egle, and S. concinna, colonies of which are usually found each year in some locality or other. Arsilonche albovenosa, Diacrisia virginica, Mamestra picta, and Pontia rapae, although not strictly gregarious, are often found in large numbers. This is particularly true of P. rapae. Probably no native species has been received in such numbers and from so many localities as this insect. As a hibernating host its status is doubtful. Occasionally a fly or two is reared, but considering the hundreds of overwintering chrysalids, the percentage of parasitism is neghgible. Ampelophaga myron feeds on Virginia creeper and gr ape; it is solitary and is usually found in small numbers. This species is con- sidered common, although none had ever been received by the writers until 1920. It is single-brooded and hibernates as a pupa, and al- though the collections of this year were heavily parasitized by A panteles congregatus Say, only a single specimen of Compsilura was recovered from overwintering material. Paonias myops, solitary usually but sometimes found in consider- able numbers on wild black cherry, appears to be of little conse- quence as a winter host. Im the collections 7rogus spp. (brullez Prov. and canadensis Prov.) and Apanteles smerinthi Riley assume prime importance as natural checks. Sphinx gordius, of the same general habits as Paonias myops but with a more varied list of food plants, occupies about the same host status. Diacrisia virginica is without doubt the most favored overwinter- ing host yet recorded. It is common; a specimen is frequently found here and there and sometimes in the most unexpected places; still it has never been received in abundance. So much difficulty has been experienced in the rearing of Mamestra picta that the records are far from complete. The larve are gregarious in the first three stages at least, after which they disperse. The species seems particularly subj ect to disease and the hibernating pupe nearly always succumb. If disease is as prevalent in the field as it is in the trays, the chances are slight of its being of much im- portance as an overwintering host. Callosamia promethea has been abundantly received from Rhode Island and Connecticut as cocoons and only upon a few occasions ’ That a higher percentage of parasitism upon the gipsy nfoth could be reached in an area where there is a mixed infestation of gipsy and brown-tail moths is not borne out by the parasite records. A careful study of these records over a series of years when one or both of the species were present indicates that a very small percentage of the flies issuing from the brown-tail moth are able to attack the gipsy moth. The few that do must necessarily prey upon larve of the last stage and here success would not be at all certain. It is doubtful, even though a considerable number of this first generation attacked the gipsy moth, whether their presence could offset the lost efficiency of the parent fly caused by the drain on its reproductive capacity in its attack upon the brown-tail moth. Accord- ing to Culver (2, p. 9), all that can be expected of Compsilura is an average progeny of about 100. Naturally, in a mixed infestation, the parasite would attack Tee first host that made its appearance. This would be the brown-tail moth. Finding the larve abun- dant and favorable, it would prey upon this host until the appearance of the. gipsy-moth larve two weeks or so later. By this time its reproductive capacity would have been reduced by the extent of its attack upon the brown-tail moth, and consequently it would be less effective against the gipsy-moth larve. HOST RELATIONS OF COMPSILURA CONCINNATA mi has it given forth Compsilura. Whatever may be its status as a sum- mer host, it is certainly of minor importance as a hibernating one. There is only one record of an abundance of Papilio polyxenes. Usually the larve are solitary. A great many adults have been reared and Compsilura often secured. ‘The collections indicate a partial second generation, the insects passing the winter as chrysalids. P. troilus is seldom of economic importance and is similar in its life history to P. polyxenes. Undoubtedly it is common, although collec- tions have been received only during the last three years. It is one of the most acceptable hosts; and, were it not restricted to certain food plants (sassafras and Lindera), it would rank high in impor- tance as a hibernating host. Collections totaling 65 larve made dur- ing September, 1920, gave 24 adult Compsilura the following spring—a record for hibernation far ahead of any other met in the writers’ studies. As many as five individuals have been known to winter successfully in one host chrysalid. Apatela furcifera and A. brumosa are strictly solitary and, al- though never plentiful, seem constant in their appearance each year. There is great difficulty in satisfactorily determining the species of the genus Thanaos, and so the larve have been separated according to their food plant. It is only those species which feed upon the oaks that are of immediate concern. Adults, identified as 7’. juvenalis Fab. and 7’. horatius Scud. and Burg., were reared from these collec- tions. Some of the species have at least a partial second generation and the larve are found in the field from July to October. Though solitary, they are sometimes found in abundance. Compsilura has been reared from larve collected in August, the parasite issuing a few weeks later and also on two occasions from larve collected in the fall, the parasite issuing the following spring. The host value of the entire group is uncertain. GENERATIONS OF COMPSILURA As will be seen by reference to Table 2, the time of emergence of Compsilura varies from year to year. Doubtless this factor is greatly influenced by climatic and environmental conditions as would also be the number of generations. However, in order to estimate the field appearance of the various generations, there must first be chosen what seems to be an average year. For this purpose, let us say that the period of emergence for the first generation extends from May 24 to June 15. Allowing an 18-day longevity period for the adults,‘ this would extend the range of the first generation to July 3. Grant- ing 30 days for a second generation and a longevity of 18 days for the adult, we would then have flies of the second generation from June 24 to August 22. At the time of the first emergence of the individuals of the second generation, there are still many adults of the first generation in the field. Thirty days later (July 24) adults of the third generation would begin to appear, and it is perfectly possible that stragglers of this generation would be found as late as October. During an extremely mild season a partial fourth gen- eration, the adults of which would issue August 24 and later, is not at all unlikely. Culver (2, p. 16) found that the fertilized females would live for an average of 18 days ua pn nerene and that mated males would live a few days longer. Unmated flies lived ut a sho ime. 8 BULLETIN 13863, U. S. DEPARTMENT OF AGRICULTURE The range of Compsilura and the overlapping of generations may be given as follows: First generation, May 24 to July 3 (40 days); second generation, June 24 to August 22 (59 days); third genera- tion, July 24 to October 1 (69 days) ; fourth generation, August 24 to November. For the most part it is the progeny of the second to fourth genera- tions that hibernate, for it is rarely that a collection made before September 1 gives Compsilura in the spring. There are exceptions, however, one collection being dated August 22. STATUS OF SUMMER HOSTS During the latter part of May and the early part of June, Comp- silura finds at hand a good many insects favorable for its develop- ment. The flies that issue first attack the hosts then accessible, and the flies that issue later attack not only those but many more. In Table 3 are listed the known hosts of Compsilura, the horizontal black line indicating the presence of host larve in the field at the time when they are subject to the attack of the parasite. The records indicate that, although Compsilura may successfully attack early- stage larvee, the intermediate stages are more acceptable. TaBLE 3.—Host list of Compsilura concinuata, showing the field appearance of the insects based upon the larval collections received at the ginpsy-moth laboratory | | Hosts | May | June } ; ——— — — | | | i } | | July | ang. | Sept.| Oct. ‘Nor. Dec. Jan Feb. | Mar. Apr. | j Aglais milberti Godart_____| Alypia octomaculata Fab- | | | en ed es Pe and Abbot (22 tie 3 t) ee Anosia plexippus Linné_-.- Apatela americana Harris__: Apaitela furcifera Gueneé___ are Apatela brumosa Gueneé-- aan Apatelatspsc io: Ps i gees | Arctiiddlarvss = 2. oy 3. @e<2ce ereece ceeee= eoeees cee e a= 22 eees eeeece (eee ece eeeses emcees sen ees eee ee= eneece Autographa brassicae Riley Automeris io Fabricius____- Basilarchia archippus Sern Ss gael Be ea AES ee Basilarchia astyanax Fab- | ApS esse eee ste! Naa 9 fe Et be Callosamia promethea Wray 2 eds. eee Pee Bees Eee Poe ers Sa ——— Calpe canadensis Bethune_-| ——/____ ! Catocolaisp=2.— = | a Cerura occidentalis Charidryas nycteis Double- day and Hewitson._2____|— | Ie Cingilia catenaria Drury __- x Be, SE Cirphis unipuncta Ha- “ILO | eas Sere peta (en) eeabae 1 Pee ite be aS hPa 8 | i } | Te eae eG ———— epee BEN Croesus latitarsus Norton-- i . Period in which hosts are subject to attack; ..-.---- period of hibernation (indicating hibe- nating hosts from which Compsilura has been reared). Adults of Compsilura concinnata issue from hibernating hosts April to June. HOST RELATIONS OF COMPSILURA CONCINNATA 9 TABLE 3.—Host list of Compsilura concinnata, etc.—Continued Hosts Datana angusii Grote and Robinson_..._.......---. Datana integerrima Grote and Robinson___.._..-__- Datana major Grote and Robinsons ee ee Datana ministra Drury___- -- Datana’ perspicua Grote and Robinson s.__22.52--- Deidamia inscriptum Tarn Seman Gee see ee 2 oe ae Ennomos_ subsignarius tb mers ope ee oe Epicnaptera americana PEL ATTIS Bae seat ae he Ian Estigmene acraea Drury... Euchaetias egle Drury __--- Eugonia j-album _ Bois- duval and Leconte____.-- Kuproctis chrysorrhoea himnéson eh ee Euvanessa antiopa Linné_- Evergestis straminalis ELD Mer ee ee ee Halisidota caryae Harris__. Halisidota tessellaris Smith Hemaris thysbe Fabricius-- Hemerocampa leucostigma Smith and Abbot________ Hemileuca maia Drury-.__- Heterocampa guttivitta Woalkers# tho GAY" fais Heterocampa umbrata Walk eres: Fikes ete id.) Hydria undulata Linné_-___ Hyphantria cunea Drury-- Lycia cognataria Gueneé___ Malacosoma americana Habpricius= 2 es aie EMT DMe ne te Pr eae Ae Notolophus antiqua Linné_ Olene basiflava Packard.___|. lene spe eet tee Se ee Paonias myops Smith and PAD DOU Ses keuay canteens. Papilio polyxenes Fabricius Papilio troilus Linné______- Papilio turnus Linné______. Pheosia rimosa Packard_--- Phigalia titea Cramer___-__- Phlegethontius quinque- maculata Haworth_____-- 56991—26——2 May | June} July | Aug.| Sept.| Oct. Dec. | Jan. | Feb. | Mar.| Apr eeecsece|sceeee| macaw ean| ee eeen|cecocos eeereee|meceece(eoeoes| ewe oee|eocoees ece|eceeces| came ee| comer ce|ewemenl|oro-aem eee|eweeeres|enceea|ocoscees|coescac|~ocoes wocees|ooo-es 10 BULLETIN 1363, U. S. DEPARTMENT OF AGRICULTURE TABLE 3.—Host list of Compsilura concinnata, ete—Continued | T } } Hosts | May | June | July | Aug. sept. | | | i Oct. Nov. Dec. Pyrophila pyramidoides | Gucnetss ae hee peop ty Rhodophora florida Gueneé | | ee eae | Samia cecropia Linné--_-_-- | Schizura concinna Smith | andvAbbOb=e: =o. ke Schizura unicornis Smith | | ANGYAD DOG 2s Bolantene libatrix Linné_| eee abbotii Swain- | i —_— eee ir rr rr err eer ee ene en ene eee j Sphingid danvee. Joe eel Sphinx gordius Stoll_______- | | | Pteronidea coryla Cresson__ hag = Neurotoma fasciata Norton_ | Vanessa atalanta Linné____ | Vanessa huntera Fabricius_, ian oa | | There is a great variety of insects among the summer hosts of Compsilura. Three orders are represented and in the Lepidoptera 18 families are included. The species attacked are widely divergent in habit as well as in external appearance. Apparently there are no distinguishing characters peculiar to the host insect. Just what means Compsilura uses to select its host is not known. It is possible that it has no sense of discrimination. Experiments positively show that year after year it will attack hibernating brown-tail moth caterpillars without the least chance of survival. “The same behavior has been observed in its relation to Olene basifiava. During the winter of 1922 C. F. W. Muesebeck of the gipsy-moth laboratory, while dissecting some of the overwintering larve of O. basiflava, found a single hibernating larva of Compsilura. It seems certain that the parasite would here meet the same fate as it does in its attack upon the brown-tail moth, but since the writers have been unable successfully to rear many of the overwintering larve of the host there are insufficient data to settle this point. It is probable that in most cases the death of the parasite is due to the lack of cor- relation between the host and the parasite; that is, in the spring, the development of the parasite exceeds that of its host, thereby result- ing in the death of both (7, p. 220). Culver (gipsy-moth laboratory records) found in his laboratory experiments that, although Comp- silura would in many instances larviposit upon the last- stage cater- pillars, the results were seldom successful. He found that the silk- worm (Bombyx mori L.), when attacked in the advanced stages, would often complete its cocoon and the parasites reaching the adult stage would be unable to escape therefrom. He also noted larviposi- tion on a chrysalid of Pontia rapae which achieved no results. There are other records of attempted larviposition upon lepidopterous pupe, all of which resulted in failure. In the laboratory experi- ments, larve of several species have been attacked, but no progeny obtained. It is these facts which lead one to believe that Compsilura uses but little discrimination in its choice of hosts and that it will waste much effort in futile attack upon an unsuitable one. HOST RELATIONS OF COMPSILURA CONCINNATA ll LIPARIDAE Among the host insects readily accessible to Compsilura in the spring are species belonging to the family Liparidae. Two of these in particular, the brown-tail moth (Huproctis chrysorrhoea L.) and the satin moth (Stilpnotia salicis L.), are species hibernating as larvee and periodic in their abundance. Both of these insects seem to be firmly established in Massachusetts. Although chrysorrhoea has several introduced tachinid parasites of importance, it would appear that salicis has none of consequence except Compsilura. Without doubt these species are primary hosts. The remaining species, the gipsy moth (Porthetria dispar L.), the white-marked tussock moth (Hemerocampa leucostigma S. and A.), and the rusty tussock moth (Votolophus antiqua L.), hibernate in the egg stage. As Compsilura does not habitually attack larvee that have not reached the third stage, its attack upon these species is somewhat later than upon those liparids which hibernate as larve. In abundance, P. dispar exceeds all of the others by far, and for this reason would naturally be the most advantageous host for Compsi- lura. Because of the great number of this host, Compsilura need waste no time hunting for a more suitable one, but attacks this species with a vengeance. With such an abundance of favored host material, it follows that Compsilura could reproduce at best and increase in such proportions that there would be at the close of the gipsy-moth season the maximum number of individuals in the field. This is most fortunate, for from now on there is no general infesta- tion of insects to replace the gipsy moth and Compsilura must seek out its host.2 At times, naturally, there might be in certain localities an ample supply of favored ones, but more often it would be a case of finding a solitary or at least a less abundant species. On the other hand, it may be that because of the fact that there are so many Compsilura in the field the hibernating hosts in and adjacent to a heavily infested area are eventually reduced to a minimum, thereby causing a shortage of winter hosts. Since the amount of parasitism of the gipsy moth by Compsilura is governed largely by the abun- dance of the first generation, less parasitism should be expected in a heavily infested area. An apparent corroboration of this reasoning appears in the parasite records of the gipsy moth laboratory, which show that the high percentages of parasitism are invariably from the lightly infested areas. In the opinion of the writers, this con- clusion is not justified by the facts, the records merely representing a percentage method of reckoning. It seems certain that there is an equal distribution of Compsilura over the entire infested area (fluc- tuations from year to year in certain localities, due to various causes, excepted) and that if the number of parasites were based upon the _°A factor of considerable importance pertaining directly to this subject is that of the dispersion of Compsilura. For several reasons the collections of native larve examined by the writers shed but little light on this point. Culver (2, p. 7) places the spread of _ Compsilura at approximately 25 miles per year, basing his claim upon scouting and larval collections, rather an unsatisfactory way to obtain notes on the dispersion, but neverthe- less about the only data there are to go by. Tothill (9, p. 39) found Compsilura 3 miles away from the colony site two weeks after liberation. This definite record, together with Culver’s deductions, would indicate that the tachinid was a strong flier and that under certain conditions 9 yearly spread of 25 miles might be expected. 12 BULLETIN 1363, U. S. DEPARTMENT OF AGRICULTURE proportionate number of larve per locality the ratio would be approximately the same. Hemerocampa leucostigma and Notolophus antigua are apparently double-brooded. Larve of these species can be found in the field from June until October. The periodic abundance of the former, usually during the latter part of July, makes it a very desirable host. JV. antigua is not at all common but what collections have been obtained usually gave forth a few specimens of Compsilura. Stud- ies made by the writers indicate that it also is a desirable host. There are but few insects among those studied where the competi- tion between the tachinid parasites is so keen as in Hemerocampa leucostigma. From data secured by Wooldridge * in 1910 we find in H. leucostigma, besides a great number of hymenopterous parasites, seven species of Tachinidae:* Compsilura, Phorocera claripennis Macq., Tachina melia Walk., Frontina aletiae Riley, Prontina fren- chit Will., (Fxorista) Zenillia amplexa Coqg., and Winthemia quad- ripustulata Fab. Of these tachinids the first four species were the more numerous. The following year collections were again made from this locality with similar results. No collections were received at the laboratory from 1912 to 1915. In 1916 several small ones were sent from Westerly and Newport, R. I. Only one species of Tachinidae was recovered, Compsilura concinnata. In 1917 five collections were received from points in Rhode Island and Connecticut and from these were reared 14 Comp- sulura and 2 Zenillia amplezxa. The infestation of Hemerocampa leucostigma at Westerly, R. L., reached its height in 1918, and from seven collections of material sent from this locality there were reared, besides Compsilura, a few Tachina mella, Frontina aletiae, Phorocera claripennis, and several unknown larviform puparia. The parasites obtained in 1918 were somewhat similar to those secured in 1910 and 1911. The native © tachinids were far less abundant, however. Owing to the great decrease in the infestation at Westerly, R. L, in 1919, only two small collections were received from there that year. These collections gave forth 10 Compsilura and 1 specimen © of Frontina frenchit. It was not until 1920 that there was really an abundance of the species around Boston. The results of the rearings of this year were not sufficient to check the findings of 1910, but they show clearly that Compsilura was the most efficient tachinid parasite present. In fact. only one specimen of native Tachinidae was obtained—Phorocera claripennis. In 1921 there was a small outbreak of Hemerocampa leucostigma at Everett, Mass., near Boston. A collection of over 500 larve of various stages was received at the laboratory, and from these were reared 4 specimens of Apanteles melanoscelus Ratz. and 68 tachinid © puparia. These puparia were all Compsilura. The following year collections were again made in the same local- ity. Over 1,000 larve of various stages were collected, and from these were reared two species of Hymenoptera and 67 Compsilura. €Gipsy moth laboratory notes. A large outbreak of Hemerocampa leucostigma@ occurred around Boston, Mass., in 1910 and 1911. Many collections of material were received at the laboratory and considerable data concerning the parasites were obtained. 7 With a single exception (Compsilura), these tachinids were the same species as those reared by L. O. Howard at Washington, D. C., in 1897 (6) HOST RELATIONS OF COMPSILURA CONCINNATA | 13 _ Later a collection of 171 larve was obtained, but no tachinid parasite other than Compsilura was reared. It was not until a small collec- tion of five last-stage larve was received on September 20 that any of the native tachinids were recovered, two specimens of Phorocera claripennis being bred. The results obtained from the collections secured at Brooklyn, N. Y., and Philadelphia, Pa. (1921-22), are interesting. The tachi- nids recovered from this material were the same species as those bred at the laboratory in 1910 and. 1911. Furthermore, with hardly an exception, the relative importance of each species was similar. The similarity of records is probably due to the conditions existing; that is, a heavy infestation and the absence of Compsilura. It is obvious from the records that in a territory where Comp- silura is established a light infestation of Hemerocampa leucostigma is comparatively free from native tachinid parasites. Such a condi- tion would hardly exist, however, were there not some interference from the exotic parasite. To what extent this interference reaches is problematical, but two things seem assured: (1) There is no excessive parasitism by the native species in localities where the introduced parasite is absent, and (2) the host species must be materially affected by the presence of this additional enemy. LASIOCAMPIDAE — The lasiocampids Malacosoma americana Fab. (the tent caterpil- lar) and Malacosoma disstria Hiibn. (the forest tent caterpillar), although close relatives of the liparids and having some points in common, are among the most unfavorable of hosts. Their appear- ance in the field during May and early June, when there is not an overabundance of insect larve of sufficient growth for the early issuing Compsilura, would lead one to believe them most desirable. Such is not the case, however, for hundreds of larve of both species have given forth but few parasites. i It is difficult to explain why Compsilura so steadfastly ignores these species. In the case of Malacosoma: americana, where the species is of the tent-making kind, some interference might be ex- pected on account of this habit; but when the same species is isolated _and used in laboratory experiments the results are hkewise negative. Reproductive experiments, using the tent-making arctiid Hyphantria _eunea Dru. (the fall webworm) as a host, have proved that far better results can be obtained under laboratory conditions, where the larve _are not allowed to web up, than can be obtained from field collec- tions. The field collections nearly always result in failure as far as -Compsilura is concerned. It seems clear, in the latter case at least, | that the web must offer considerable protection to the larve within /it. WM. disstria, which does not make a tent, has a much better host )value than M. americana. Another species of this family, H'picnaptera americana Harr., | appears in the field at a later period and the larve are frequently ‘found during the last of August. Unlike the species of Malaco- soma, this insect is solitary and is never found in abundance. Its value as a host species is doubtful. 14 BULLETIN 1363, U. S. DEPARTMENT OF AGRICULTURE NYMPHALIDAE The family Nymphalidae offers the greatest number of host in- sects. Species of the genera Polygonia, Eugonia, Charidryas, Kuvanessa, Vanessa, Aglais, and Basilarchia have all given forth Compsilura. With the exception of Basilarchia and Charidryas, which hibernate as larvee, the life history of these hosts is similar. All except Charidryas nycteis are double-brooded, or at least have a partial second generation, and are to be found in the field from early spring until late fall. The larve are, for the most part, gregarious, in the early stages, at least. : In this group are to be found the most constant alternate hosts and in some respects the most favored. In percentage of parasitism the rate here is as high as in any other group. In the future other species of this family will no doubt be found to harbor Compsilura. It is useless to speculate, however, on the host possibilities of any species of a given group, for no matter how closely the hosts are allied, they may be unsuitable. For instance, among the arctiids we find favored hosts, such as DPiacrista virginica and Estigmene acraea, and on the other hand we find species of little or no host value, such as Hyphantria cunea, Phragmatobia fuliginosa, and Isia isabella. In behavior there is some variance. Huvanessa antiopa L. always | remains in a colony until the time of pupation and is usually found high above the ground feeding on willow, elm, poplar, and birch. Eugonia j-album and Polygonia interrogationis do not remain gre- garious for so long a period; otherwise their habits are much the same. One of the most conspicuous examples of competitive parasitism occurs in the spiny elm caterpillar (Huvanessa antiopa L.). Col- lections of this species have been constant and, for one year in par- ticular, abundant (Table 1). Nearly all of the larvee received were in the last stage. It is doubtful whether we have any other species where there are more data available for studying the relationship which Compsilura bears to a single competing tachinid than in this species. Material has been reared in bulk collections and as indi- viduals. ‘The results have been studied from every angle, and yet it is exceedingly difficult to draw any definite conclusions. Facts ascer- tained from one year’s data and corroborated by a second, or in some cases by a third, are contradicted by the results of the fourth. Con- ditions are so entirely different each year that it is useless to attempt to arrive at average results. The two tachinids playing such an im- portant part in the control of this species are the native tachinid, Pelatachina pellucida Coq., and Compsilura. The former has but a single generation and appears to be peculiar to this host alone. Not the least of our difficulties in estimating value of these para- sites is the great amount of superparasitism which occurs among them.* This is still further complicated by a good deal of multiple parasitism.? Nearly one-half of the collections received during the eight years of study is subject to the latter phase of parasitism. It _8The term “superparasitism’”’ is used to indicate that nrore than one parasite of a Single species attacks the individual host. ®The term ‘‘ multiple parasitism ”’ miGicates that two or more different species of primary parasites attack the same individual. HOST RELATIONS OF COMPSILURA CONCINNATA 15 varies in degree from year to year and is shown by the following examples: 1 larva gave 1 Compsilura and 1 Pelatachina; 1 larva gave 3 Compsilura and 1 Pelatachina; 1 larva gave 5 Compsilura and 1 Pelatachina; 1 larva gave 2 Compsilura and 2 Pelatachina; 1 larva gave 1 Compsilura and 2 Pelatachina. From material reared in bulk, 61 larve gave 67 Compsilura and 75 Pelatachina; 100 larve gave 69 Compsilura and 15 Pelatachina; 52 larvee gave 70 Compsilura and 29 Pelatachina; 80 larve gave 7 Compsilura and 107 Pelatachina. The aggregate of superparsitism far exceeds that of multiple parasitism. Individual rearings have shown as many as 4 Pelata- china to a single host and with Compsilura as many as 6 per host. Other collections from which Pelatachina alone was reared furnish striking examples of this sort of parasitism; 5 larve gave 15 Pelata- china; 89 larve gave 90 Pelatachina. There are similar records for Compsilura, some of which are as follows: 8 larve gave 23 Compsilura; 10 larve gave 50 Compsilura; 41 larve gave 108 Compsilura. The presence of a hymenopterous parasite (Hyposoter n. sp.) makes the problem still more intricate. Frequent rearings of this species were obtained during 1915 and again in 1919. In 1921, five cocoons were obtained and from these adults were secured in the spring of 1922. This species hibernating in its cocoon is one of the most difficult to rear to the adult stage. The conclusions drawn from the records of the writers indicate ‘that the presence of Compsilura is not detrimental to any great ex- tent to the native tachinid. It is realized, of course, that there is a considerable amount of duplicate parasitism and that the native tachinid may suffer somewhat through the aggressiveness of Comp- silura. On the other hand, the records show that Pelatachina emerges at least two weeks and, in most instances, three weeks before Compsilura; it is no doubt owing to this fact primarily that it is able to compete successfully with the introduced parasite. It is probable that during this period, while its attack is unhampered, its effectiveness is most pronounced and that by the time Compsilura appears the development of its progeny has progressed to such a de- gree that it is in no way affected by that species. Furthermore, the fact that Pelatachina is single-brooded and has never been recovered from the collections of Huvanessa antiopa made in summer months adds much to the credit of Compsilura. The records show that the most that can be expected from this species (Pelatachina) is its check upon the first generation; and, as the host species may be found in the field up to October, it would therefore be allowed to increase without restraint as far as that species is concerned were it not for Compsilura.? , Polygoma interrogationis Fab. is an excellent host. It is of little economic importance, and is usually found in small numbers on the elm. In New York, it is somewhat injurious to hop vines but is be- lieved to be held in check by the chalcis fly Pteromalus vanessae 10 Collections received from places outside the Compsilura territory, made during a period of two years, aggregate over 1,000 larve. From these collections Pelatachina has frequently been reared, but on two occasions only has any other tachinid been obtained. This species, Phorocera claripennis Macq. (two individuals reared), is of apparently little importance in its relation to FH. antiopa. 16 BULLETIN 1363, U. S. DEPARTMENT OF AGRICULTURE Harris (5, p. 213). The writers have never succeeded in rearing this parasite, but they have obtained records of two Hymenoptera, Am- blyteles caliginosus Cress. and Hoplismenus morulus Say. The species Aglazs milberti, Vanessa atalanta, Vanessa huntera, and Polygonia comma are nearly always found just a few feet above the ground, feeding on nettle and everlasting. The two former usually feed in colonies, the two latter are apparently not so gregari- ous. All are favorable hosts. : In its struggle with the native tachinids, there is little fear that Compsilura may not be fully capable of taking care of itself; but it is less certain that it can successfully compete with certain Hymenoptera. In the collections of Aglais milberti (1917, 1918) there are but two parasites of importance, the hymenopteron Apanteles atalantae Pack. and Compsilura. A. atalantae is gre- ee and is reared more frequently than the tachinid. The latter, owever, breeds freely upon this host, and it is a frequent occur- rence to rear five or six from a single individual. A few rearing records showing the best examples of superparasitism are as follows: From a collection of 143 larve, 34 were killed by Apanteles ata- lantae, and from the remaining larve (109) there were reared 310 Compsilura. No adults of Aglais milberti were secured. From a collection of 101 larve, 74 were killed by Apanteles atalantae and from the remaining larve (27) there were reared 41 Compsilura. A single adult Aglais milberti issued. From 19 larvee, there were reared 53 Compsilura. No host adults issued. From 26 larvze there were reared 40 Compsilura. No host adults issued. Of the two parasites, Compsilura and Apanteles atalantae, the latter has much the advantage, because of its ability to attack the host in an earlier stage. It is probable that, if any parasite which is capable of attacking the early-stage caterpillars should compete with Compsilura, the latter species would be the loser. This is the case as regards A. atalantae, for here there is a considerable number of progeny already well advanced in development before the host is subject to the attack of Compsilura. It is assumed that if the host already parasitized by A. atalantae was in turn attacked by Comp- -silura there would be but little chance for its development, since the parasites would crowd it out. This opinion is strengthened by the absence of multiple parasitism in this species. A. atalantae attacks the larva in the first and second stages only. This habit, as pre- viously noted, has its advantages; and yet, because of it, those indi- viduals which have reached the third stage and have escaped the attack of that parasite are free to develop without apparent check." It is from the third stage on that Compsilura proves its worth; and, although it probably wastes many of its progeny in futile attempts at parasitism on some already parasitized host, it nevertheless ac- complishes its purpose and must be credited with a considerable amount of parasitism. Vanessa atalanta L., a species closely allied to Aglais milbertz and similar in habits and behavior, is at times heavily parasitized by Compsilura. For example, a collection of 25 last-stage larve This fact, and also taking into consideration the rearing of a few specimens of (Ezorista) Zenillia futilis O. S. and Winthemia quadripustulata Fab., would perhaps indicate some interference from Compsilura. ’ HOST RELATIONS OF COMPSILURA CONCINNATA 17 was received from Deering, N. H., July 30, 1915, and from them 20 Compsilura were obtained. No other parasites were reared; and, since this was the only collection obtained during 1915, there are very few data concerning the species for that year. No material was collected in 1916, and only 9 specimens received during 1917. The species was plentiful during 1918, 1919, and 1920, being espe- cially abundant in 1919. The position occupied by Compsilura in its relation to this species is about the same as in A. mélberti, except that it is still more complicated by the presence of two native tachinids (frontina archippivora Will. and [FE «xorista] Zenillia futilis O. S.). The hymenopteron Apanteles atalantae Pack. is pres- ent in considerable numbers, but the true struggle lies between the tachinids themselves. There is little to guide us in determining the status of /’. archippivora. From 25 collections, this species was bred from but 4, and, except in the case of 1 collection, only 5 specimens were recovered. The exception, however, proves some- what confusing, as in this instance 17 flies were reared from 16 larvee. Biologically, the species is distinct from the other two, its method of reproduction being that of oviposition on host. The writers’ records indicate Anosia plexippus as its primary host, although Coquillett (2 p. 15) lists it from seven others, among which are two species of the genus Vanessa... Eliminating Frontina, the contest narrows to (Hworista) Zenillia futilis and Compsilura; and, although there were many more Zenillia reared in 1919 17, the results of the year previous were much in favor of Compsilura. Parasite summaries of 1918 show five times as many Compsilura as Z. futilis. The 1920 results resembled those of 1919, showing but one record of Compsilura. Apparently Compsilura has the worst of the argument and the explanation may lie in its biology. Z. futilis belongs to the masiceratine series (species whose repro- ductive habit is leaf oviposition of microtype eggs), whereas the method of Compsilura is larviposition. The latter species is double- brooded and has a number of hosts. In the species belonging to the first series the capacity for reproduction is enormous, the uterus usually containing hundreds of eggs, whereas Compsilura is far less fecund. Considering the method of reproduction of the former parasite, 1t is not surprising that it is able to work advantageously, particularly in this instance, where the host is gregarious, the larve clustered together on a limited patch of nettle. Superparasitism is obvious in a few of the collections but multiple parasitism is rare, only one instance being recorded (Z. futtiis and A. atalantae). Charidryas nycteis D. and H. passes the winter as a larva and at- tains its full growth by the middle of June. Adults issue shortly thereafter and their offspring may be found from late July until the ensuing spring. The food plants are chiefly aster and goldenrod. All of the collections have been small and infrequently received. The species is probably of little host value, since most of the larve attain their full development so early in the spring, at about the time when Compsilura emerges. 14 From 22 collections of this species, Zenillia was reared from 17 and a total of 249 | puparia was obtained; Compsilura was present in 6 collections only and only 20 puparia | Were recovered. 18 BULLETIN 1363, U. S. DEPARTMENT OF AGRICULTURE _ Species of Basilarchia are distinct from any of the above both in larval appearance and in behavior. The species archippus Cramer is most commonly received, there being only a few collections of astyanax Fab. The food plants of the former are numerous, with poplar and willow most in favor. Like Charidryas nycteis, it passes — the winter in the second or third larval stage, but not gregariously. The collections of the early-stage larve are exceedingly limited, but — there are enough data to indicate considerable parasitism by Apan- — teles limenitidis Riley. There is at least a partial second generation, — and it is not uncommon to find full-grown larvae up to frost. | Although of a solitary nature, B. archippus is constant in its appear- | ance and is often found in large numbers. Since the larve in the last stages seem to be peculiarly free from insect enemies (there — are no rearing records other than Compsilura), few species are better hosts; and, from the records, it is apparent that Compsilura has made the most of its opportunity. From a total of 81 collections, this parasite has been obtained from 35. Free from competition as — it is in this case, it its not at all surprising to find a high degree of | parasitism. Some rearing results suggestive of this are as follows: 19 larvee gave 48 Compsilura and 5 B. archippus; 17 larve gave 34 | Compsilura and no B. archippus; 10 larve gave 17 Compsilura and | _ no B. archippus,; 3 larve gave 9 Compsilura and no B. archippus; 12 larvee gave 21 Compsilura and 2 B. archippus,; 16 larve gave 26 | Compsilura and no B. archippus. Obviously there is much superparasitism, and individual rearings | have often registered from three to seven parasites per host. NOTODONTIDAE Insects of still another group, the Notodontidae, are to be classed ‘with the favored hosts. These insects commonly appear in the field in late summer and specimens can be found until cold weather puts -a stop to all insect activity. Species of the genus Datana (integerrima G. and R., ministra_ Dru., major G. and R., perspicua G. and R., and angusiz G. and R.) are gregarious and have a variety of food plants. One species or another is usually abundant in restricted localities; and, although Compsilura is commonly reared during the fall, it has never been reared from overwintering pupsx.*® For some reason, there is great. difficulty in rearing some of the Datanas and successfully overwinter- ing the pupe. This is particularly true of the walnut caterpillar (D. integerrima), a species common on black walnut. Because of its great abundance it is of especial interest as a host possibility, but owing to the heavy mortality of the larva when reared under artificial conditions, there are few data for judging its status. About all that can be said is that it has given one or more Compsilura for three years in five. It was from this host, too, that several Compsilura were reared in 1921, establishing a new dispersion record for that ‘parasite. 18 Since the above was written, Compsilura has been reared on two occasions from overwintering pupe. 4A collection of 200 fourth-stage larve collected at the gipsy-moth infestation at ‘Greenport, L. I., August 16, 1921, gave five Compsilura in September, 1921. HOST RELATIONS OF COMPSILURA CONCINNATA 19 Heterocampa guttwitta Walk. and /Zeterocampa umbrata Walk. pass the winter as pupe. ‘The former is periodic in abundance, the latter never so. It is, in fact, rather rare, only a few specimens reaching the laboratory during the entire period in which collections were made. The food plants of both are chiefly maple and beech. Neither of the species is nearly so favorable as the Datanas. Melalopha inclusa Hiibn. is a tent-making species and hibernates as a pupa. The species feeds on willow and poplar and has been re- ceived in abundance during the last three years. Frontina frenchii, Eulimnerium validum Cress., and Apanteles sarrothripae Weed seem to be its chief parasites. The species has given Compsilura several times but it can not be considered highly as a host. Pheosia rimosa Pack. is solitary; its food plants are willow and poplar. It is uncommon and only during the last year have there been received any good-sized collections. It has about the same status as the species of Heterocampa. Larve of the red-humped caterpillar (Schizura concinna 8S. and A.) are found in the field from July to October. This species hiber- nates in the prepupal stage under leaves and rubbish. Its food plants are varied, apple, birch, willow, and bayberry being much favored. It is common in many localities and is one of the insects most con- stantly received. It is at times much favored by Compsilura as a summer host, but is of little consequence as a winter one. It has on -one occasion, however, given Compsilura in the spring. In Schizura concinna, Compsilura meets with considerable com- petition from Wenthemia quadripustulata, Phorocera claripennis, Phorocera erecta, and Gymnophthalma americana Town. The last named, however, attacks the larve in an earlier stage than the rest, and its growth is so far advanced by the time the host larva is attacked by the others that it probably has no trouble in maturing. At any rate, a very good percentage of parasitism is maintained each year by G. americana. A summary of the tachinid parasites shows that the combined efforts of the native species (G. americana excepted) are less effective than that of the exotic. Such may not always be the case, however, for in its relationship to this host Comp- silura is most variable. Certain years have given but a negligible amount of parasitism, whereas others have given a parasitism as high as the most favorable host. The principal hymenopterous para- sites seem to be Hyposoter fugitivus Say and L'ulimnerium validum Cress. These species attack the host in the second and third stages, the former usually issuing from the fourth and fifth stages and the latter from the cocoons. Schizura unicornis 8. and A. is apparently a solitary species and has always been received in small numbers, usually during Septem- ber. The larvee feed upon a great variety of food plants. There is but one record of rearing Compsilura from it and that was from a full-grown larva collected in the fall, the parasite issuing the follow- ing spring. Cerura occidentalis Lint. also appears to be solitary and the col- lections of it are always small. The larve are found chiefly on wil- low and poplar. Compsilura has been reared only once, the adult issuing during August from a larva collected in July. 20 BULLETIN 1363, U. S. DEPARTMENT OF AGRICULTURE ARCTIIDAE Differing but slightly from the liparids in behavior and in ex- ternal appearance are the arctiids. Compsilura shows marked par- tiality for the species noted below. The yellow-bear caterpillar (Dzacrisia virginica Fab.) and the salt-marsh caterpillar (Hstigmene acraea Dru.) are both common species and, although solitary, are often found in abundance. They have a long period in the field, from June until November, and a great variety of food plants. ‘Both are favorable to Compsilura, particularly the former, it being without doubt one of the most acceptable winter hosts. The tussock caterpillars Halisidota caryae Harr. and Halisidota tessellaris S. and A.?° are gregarious. They are general feeders and are occasionally reported as injurious. There is but one generation, the insects pupating in the fall and passing the winter in that stage. Several of the collections have given hymenopterous parasites, especi- ally those of ¢essellaris, but there are few records of Compsilura. Of the two species, caryae is the most favorable. Euchaetias egle Dru. is also gregarious but, unlike the species of Halisidota referred to above, its food plants are limited and it has never been found by the writers on anything but milkweed. In New England it is apparently single brooded; the larve are usually found in August and September, pupating “during the latter month and hibernating in that stage. There are a number of parasites both hymenopterous and tachinid, the latter perhaps being the more common. Not only does this species serve as an admirable alternate, but it is also an excellent hibernating host. Four of the five tachinids often bred from /’ egle are the same species as those secured from Hemerocampa leucostigma,; that is, Compsilura, Tachina mella, Phorocera claripennis, and Frontina french. Several other species of this family, solitary in nature, and as yet undetermined, have yielded the parasite. On the other hand, certain species previously cited are for some reason or other seemingly un- suitable. NOCTUIDAE, AGARISTIDAE, AND PYRALIDAE In the family Noctuidae are found the most divergent forms both in behavior and in external appearance. Species belonging to the genera Apatela, Arsilonche, Mamestra, Catocala, Nadata, EKuthisa- notia, Calpe, Pyrophila, Plathypena, Scoliopteryx, Autographa, Cirphis, Plusiodonta, and Rhodophora have all yielded Compsilura. Only one of these, however, Autographa brassicae, has been at all constant in its abundance; and, although Compsilura has been oc- casionally reared from it, there is little to be said in its favor. In the collections, it is always closely associated with Pontia rapae and, like that species, has but few parasites. Apatela americana Harris is rather a common species, but it is never received in large numbers. It is usually found late in the fall feeding upon maple, oak, and other growth. It is solitary and passes the winter as a pupa. Compsilura and JZachina mella have been 15 Halisidota tesseliaris is perhaps found more often, in the last stages, as a solitary rva. HOST RELATIONS OF COMPSILURA CONCINNATA 21 reared from overwintering material. Rogas stigmator Say has also been bred, five adults issuing in September from a larva collected during that month. Collections of Apatela furcifera Guen. extend over a period of seven years. The larve are found in the field from the middle of June until the latter part of September. The food plants of this species seem restricted to the various varieties of cherry.. It is not considered uncommon, although it has never been received in abund- ance. From these collections (83 individuals) there has never been reared any other tachinid than Compsilura. On three occasions only have any hymenopterous parasites appeared, species belonging to the genera Apanteles, Meteorus, and Rogas being bred. A. furcifera is of first importance as a summer and winter host of Compsilura. Apatela brumosa Guen. and another species of Apatela as yet undetermined are never found in abundance but are received in small numbers each year. The insects are usually found in the woodlands, principally on willow, birch, cherry, and oak. Larve of these species may be found in the field from the middle of June until September and, although never abundant, are among the most sought of the host insects. | | Calpe canadensis Beth. appears early in June; it is common and sometimes plentiful. ‘There seems to be but a single generation, the adults issuing during July. The larve feed principally upon meadowrue (Thalictrum) and are somewhat difficult to find because of their protective coloration. Perhaps because of this, only a limited number of Compsilura has been bred. | Scoliopteryx libatria L. is either double-brooded or else has a very remarkable larval stage. It is a rather rare species in the writer’s collections, only 12 specimens having been received in eight years. It is said to hibernate as an adult, the food plants being listed as willow, poplar, and cherry. Unlike many of the noctuids it does not enter the soil to pupate but transforms within its cocoon attached to the twigs of the host plant. Like Calpe canadensis, the species is well protected by its coloration and has given a few Compsilura. _ The zebra caterpillar (Mamestra picta Grote), Mamestra legitima Grote, I. adjuncta Boisd., and Pyrophila pyramidoides Guen. are all acceptable as hosts to Compsilura. They are, as a rule, garden- crop insects, and the two former are at times very abundant. All of them hibernate as pupe beneath the soil. Arsilonche albovenosa is ordinarily found on marshland. Cat- tail (Typha latifolia L.) and the various marsh grasses are, its chief food plants. It ranges in the field from June until October, hiber- nates as a pupa, and is considered a favorable host. Besides Comp- silura, another tachinid, Mfasicera sp., overwinters in this host. There have also been two hymenopterous parasites bred, Rogas stig- mator Say and Microplitis quadridentatus Prov. Euthisanotia grata Fab. is rather uncommon. It appears in the field during the latter part of July and feeds principally on grape and Virginia creeper. It is an acceptable host, but the collections have been small and the data give little idea of its true status. Nadata gibbosa S. and A. is a species not uncommon, appearing in the field during July and August and overwintering as a pupa. 16 William Reiff, Forest Hills, Mass., 1913. 22 BULLETIN 1363, U. S. DEPARTMENT OF AGRICULTURE Food plants are given as maple, beech, and birch. It is a favorable host for Compsilura. The green clover worm (Plathypena scabra Fab.) was abundant for one year only. Several good-sized collections were obtained and from them were reared Compsilura, Winthemia quadripustulata,,. and Archytas aterrima Desv. -The speciés feeds chiefly on clover but at times causes considerable injury to the pea and bean crops. Hibernation takes place in the adult and pupal stages. Plusiodonta compressipalpis Guen. and Rhodophora florida Guen. are present in the locality, but they have never appeared in the: laboratory collections. Both of the records are from Reiff ?* rear-- ings. The species probably hibernate as pupe. The army worm (C7rphis unipuncta Haw.) is a favorable host for Compsilura. It is found throughout the entire season from. May until frost. Hibernation is in the caterpillar stage usually, although the insect is said to overwinter sometimes as an adult. It is of national importance, and serious outbreaks, either locally or over a wide area, are not uncommon. ‘Tachinid flies play an important part in the natural control of this species and their success: has probably increased since the advent of Compsilura. During the last eight years only a few collections of C. unipuncta were received at the laboratory, but in 1914 several good-sized collections. were secured. From these collections there was obtained a very good percentage of parasitism by Compsilura. In the various host and parasite lists where this species appears there are many tachi- nids recorded but only five of them have been reared at the labora- tory. Of these native parasites, Winthemia quadripustulata Fab. is the only one of consequence and the recoveries of this species, although many times greater than all of the rest combined, are not comparable to Compsilura. For example: Six collections, totaling nearly 1,000 larvee (from six localities) gave nearly twice as many Compsilura as Winthemia. The eight-spotted forester (Alypia octomaculata Fab.) is received. commonly in small numbers and was once obtamed in abundance. The species feeds on grape and woodbine. It hibernates as a pupa and is of little host value. The records show three native tachi- nid parasites, (Haorista) Zenillia eudryae Town., Chaetophlepsis tarsalis Town., and Winthemia quadripustulata Fab., and a few Compsilura. A summary of the parasite records would indicate the superiority of the native species. Evergestis straminalis Hiibn. is of little or no host value at the | - present time. It is constant in its appearance, however, and might, should there be an absence of favorable hosts, prove more worthy. The insect is found in gardens feeding mostly on radish and turnip. It hibernates as a pupa beneath the soil. | Catocala sp.: The great difficulty experienced in separating the | larvee of this genus necessitated their treatment as a single group. There are at least five species represented in the collections. In most cases the larve have been received in small numbers during” May and June, sometimes in July. Compsilura was recovered from two larve collected in June, 1922. Catocala is of doubtful host value. HOST RELATIONS OF COMPSILURA CONCINNATA yr. “ GEOMETRIDAE Phigalia titea Cram. was very abundant for several years but is. now scarcely to be found. It has a variety of food plants, chiefly oak, elm, and chestnut. It appears in the field early in June and hibernates as a pupa. It is not a satisfactory host for Compsilura. Hydria undulata L. is a somewhat common, gregarious species, the larvee of which web together the leaves of wild black cherry. AlI- though a great number of collections have been received at the laboratory, it was not until 1922 that Compsilura was recovered. The recovery of 2 adults from 6 larvee in one case and 11 adults from 200 in another would ordinarily be considered a fair host record, were it not for the fact that all the past collections have resulted in failure. In all probability this host was abundant at a time when there was a shortage of favored ones. Ennomos subsignarius Htibn. is a gregarious species and was found in great abundance for three or four years, less abundantly the fifth, difficult to find the sixth, and entirely absent the seventh and eighth years. Larve appear in the field early in May, com- plete their larval stages in June, and issue as adults in July. The species feeds on red maple principally and hibernates in the egg stage. It has never been a much favored host. Cingilia catenaria Dru. has been received in abundance only dur- ing the last four years. It appears in the field during late June and has a great variety of food plants, including false indigo, birch, huckleberry, and cherry. The species hibernates in the egg stage. It has given a considerable number of Compsilura and has a better host value than any other of the geometrids. Lycia cognataria Guen. and an unidentified geometrid are solitary and are never found in abundance; the former feeds on willow and hibernates as a pupa. As host insects their value is small. LYMNADIDAE Anosia plexippus LL. was received in abundance in 1918 and in smaller numbers the two preceding years. During 1919 to 1921, inclusive, there were no collections received. In 1922, the insect was found in small numbers and the 14 collections received represent only a few individuals. The species is still scarce. Without exception, its food plant is given as milkweed. The species is migratory and winters as an adult in the Southwest. Three native parasites are recorded from it and one of these, Prontina archippivora Will., 1s of prime importance. The two remaining species (Wénthemia ob- scura Coq. and [E'xorista] Zenillia vulgaris Fall.) are apparently of little consequence. Frontina appears to meet but little opposition from Compsilura and the sum total of its parasitism is much greater. Over 50 per cent of the collections have given Frontina, whereas Compsilura was recovered from only 11 collections. Superparasi- tism is common with both species but particularly with Frontina, where the average from one collection of 22 larve was 4.86 per individual. The best records found for Compsilura are three adults per individual. Multiple parasitism is uncommon, there being no instance noted by the writers. In a general way, Anosia can be considered a favorable host for Compsilura. 24 BULLETIN 1363, U. S. DEPARTMENT OF AGRICULTURE PAPILIONIDAE The species. Papilio polyxenes Fab. and Papilio troilus L. have been discussed elsewhere in this bulletin. Papilio turnus L., a species similar in habit to the others of its genus, has given Comp- silura frequently. It is very probable that the future will show this species to be of the same host value as its relatives. PIERIDAE The cabbage worm (Pontia rapae L.) is nearly always to be found in abundance in some locality or other. It hibernates in the chry- salid stage. It is an acceptable host and, because of its abundance and wide distribution, possesses a certain attractiveness. In 1910, Tothill (7, p. 223) succeeded in rearing a great many flies and, in © some instances, a total of 40 per cent parasitism was obtained. Some years later, Culver,’ who had received large collections of this ma- terial for life-history work, recorded a fair amount of parasitism, but in no case did he equal the record of the former investigator. In contrast to these records, however, the data obtained by the — writers show but little parasitism. . SATURNITIDAE Callosamia promethea Dru., Telea polyphemus Cramer, Samia | cecropia L., Automeris io Fab., and Hemileuca maia Dru. are five | species of doubtful host value. From the last-named Compsilura has | been reared occasionally, but considering the hundreds of larve of © all stages used in the experiments, the host value of this insect is © insignificant. : As has been previously stated, the value of Callosamia promethea Dru. as a winter host for Compsilura appears to be negligible. Its status as a summer host is apparently much more important. Since | Culver 1 found, while experimenting with this species and Comp- | silura, that he could readily obtain larviposition and successfully © rear adults when using early-stage caterpillars, there seems little © doubt that were large collections of early-stage larve received, a fair amount of parasitism would be recorded. | The collections of Telea poly phemus Cram. have nearly always been made in the pupal stage and no Compsilura were recovered from them. It is sufficient to say that, in three separate collections of one larva each, there were obtained two Compsilura from one of them. Samia cecropia Li. seems to have about the same host status as 7. polyphemus. ‘The material when collected as cocoons has never given Compsilura. Larval collections, however, show better results. A — single instance of the rearing of four flies from nine third-stage and fourth-stage larve is recorded. Automeris io Fab. has a greater host value than any of the satur- niids mentioned. Although none of the collections received prior to 1922 has given Compsilura, the recoveries made that year were grati- fying. Furthermore, all of the material was from New York, at points well outside the gipsy-moth area. From these records there 17 Gipsy Moth Laboratory Records, 1917-18. HOST RELATIONS OF COMPSILURA CONCINNATA | 25 was established a new dispersion line for Compsilura. (Phorocera claripennis Macq. was the only other tachinid reared.) SPHINGIDAE Deilephila gallu Rott. and Deidamia inscriptum Harr. have both been taken abundantly near lights, but they appear only occasionally in collections received by the writers. The larve of both species appear in the field from July until October. The former. feed on Galium and primrose, the latter on grape and Virginia creeper. Both species hibernate as pupx. Their host status is favorable. Deilephila lineata Fab. was received intermittently over a period of eight years. The larve are usually found feeding on Portulaca. There are probably two generations, the later one hibernating as pup. Most of the collections were received during September and October. An exception to this was the receipt of one last-stage larva collected July 21, from which two Compsilura emerged August 14, 1922. The host status is favorable. The northern tobacco hornworm or tomato worm (PAlegethontius uinguemaculata Haw.) is constant in its appearance and is in the Feld from July until October. It feeds on tomato and hibernates in the earth as a pupa. Asa summer host it has occasionally given Compsilura, and in all probability would be one of the most favored were it not for Apanteles congregatus Say. In this hymenopteron P. quinquemaculata finds its worst enemy, and it is with difficulty that specimens of mature larve are obtained free of this parasite. Possibly on account of its great size a number of the larve harbor both Apanteles and Compsilura. As many as three adult Compsi- lura per larva have been obtained from material previously para- sitized by Apanteles. The species should be a good host for overwin- tering Compsilura, but since it is difficult to handle in confinement during hibernation there are few data on its fitness. Hemaris thysbe Fab. has been received but three times in eight years. It has about the same life history as Phlegethontius quinque- eee and feeds chiefly on Viburnum. It is a very acceptable ost. HESPERIIDAE AND CERATOCAMPIDAE Epargyreus tityrus Fab. has been received in good-sized collec- tions only once in eight years. The species feeds on a variety of — food plants, principally locust (Robinia pseudoacacia L.) and groundnut (Apios tuberosa Moench). It appears in the field during July, and specimens are to be found until late October. It hiber- nates as a pupa and is of fair value as a host. The parasitism by _ the Hymenoptera is negligible, as is also the case with the tachinids _ other than Compsilura. This fly alone has been reared in consider- _ able numbers, especially during 1921. _ The orange-striped oak worm (Anisota senatoria S. and A.) 1s _ abundant at times and has been received in particularly large num- | bers during the last two years. The species feeds principally on oak and hibernates as a pupa. A few of the collections have given Compsilura, but the native parasites predominate. Among the || tachinids, Frontina frenchii Will., Winthemia quadripustulata Fab., (Euorista) Zenillia ceratomiae Coq., and Stwrmia sp. were reared. 26 BULLETIN 1363, U. S. DEPARTMENT OF AGRICULTURE The principal Hymenoptera were Hyposoter fugitivus Say and Apanteles anisotae Mues. A number of collections of the green-striped maple worm (Ani- sota rubicunda Fab.) were received during 1919 and 1921, most of them coming from Western Massachusetts and New Hampshire. Usually A. rubicunda is to be found in company with Heterocampa guttivitta. The species feeds principally upon maple and hibernates as a pupa. Several specimens of Prontina frenchi: Will. and a species of Sturmia have been bred. There is but one rearing record credited to Compsilura. COCHLIDIIDAE Native species of the family Cochlidiidae are rarely sent to the laboratory and none have ever given Compsilura. Collections of the exotic oriental moth Cnzdocampa flavescens Walk. were received in large numbers during 1917 and 1922. The species has but a single generation, the winter being passed in the prepupal stage. During 1922 weekly collections of the larve were received, aggregating nearly 1,200 individuals. From this material a single Compsilura was reared, the adult issuing in September. ‘The host value of the species is apparently slight. TENTHREDINOIDEA - The large elm and willow sawfly (Cimbex americana Leach) is constant in its appearance and is in the field from July until Sep- tember. Only once during a period of eight years has it been abun- dant and then the infestation was confined to a small area. Willow and elm seem the most favored food plants. There is but one gen- eration, the last-stage larva burrowing in the ground and forming its cocoon, where it passes the winter as a larva, pupating in the spring. It offers little attraction to Compsilura. Croesus latitarsus Nort. is a very common species found abun- dantly each year on gray birch. It has at least a partial second generation and larve of this species are in the field from the middle of June until October. The larva passes the winter within its co- coon and pupates in the spring. It is possible that Compsilura at- | tacks this species more than is recognized, for the examination of — cocoons has revealed a certain amount of unlooked-for parasitism — that may be of considerable importance. Dissections have shown that | in some instances the cocoons contained adult Compsilura which were — ‘ unable to work their way out. Culver (gipsy-moth laboratory rec- ords) made a similar finding in his experiments with the last-stage | larve of Bombyx mori, the larve being freely attacked, the parasite maturing within the host pupa and being unable to emerge because | of the tough cocoon. | Neurotoma fasciata Nort. is a gregarious species commonly re- | ceived each year in fair abundance. The larve feed upon cherry, | webbing the leaves together and leaving their nest only when they | seek the earth for hibernation. The period of hibernation in New | England usually extends over two seasons. (Larve collected in Sep- | tember, 1920, gave adults in May and June, 1922.) Owing to the extreme difficulty in overwintering the prepupe, very few. adults — have been obtained. At most, the parasitism of this species by © Compsilura is negligible. | HOST RELATIONS OF COMPSILURA CONGINNATA Ot Pteronidea coryla Cress., a rather uncommon species, has been re- ceived at the laboratory but twice, in June and September, 1921. Evidently there are two generations, individuals of the later one passing the winter in their cocoons, the adults issuing the following spring. The larve are gregarious and feed in colonies on hazel nut (Corylus americana Walt.). The collections, aggregating about 100 larvee, gave mostly adults, there being but one parasite, Compsilura, a female fly issuing in July, 1921. The imported currant worm (Pteronidea ribesi Scop.) has been abundantly received over a period of eight years. There are two or at least a partial second generation, cocoons ** of either generation overwintering in soil. It is of very little, if any, importance as a host, for Compsilura has been reared from it on only one occasion. COLEOPTERA So accustomed have we grown to the ever-increasing host list of Compsilura that a new record obtained from some lepidopteron causes but little comment. There have been but few collections of coleopterous larve, however, and none has ever given the parasite. A rearing attended by peculiar circumstances was reported to the writers by C. W. Johnson, of the Boston Society of Natural History, who in 1914 recovered the parasite from the white-pine weevil (P%s- sodes strobi Peck). In September of that year he was looking over some of the mounted specimens of various insects in the Libby Museum at Wolfboro, N. H. One mount containing a terminal shoot of white pine, illustrating the work of the weevil, contained a fly which seemed out of place. Upon inquiry it was found that the mount had been made up as usual and that the fly must obviously have issued after the mount was completed. At Johnson’s request the fly was given him, and he identified it as Compsilura concinnata. Since there was no puparium in sight, the maggot evidently pupated ‘within the burrow of the host. RECORDS OF COMPSILURA REARINGS OTHER THAN THOSE RECORDED AT THE GIPSY MOTH LABORATORY The writers are indebted to D. W. Jones, of the European Corn Borer Laboratory, Arlington, Mass., for the following notes on ‘Compsilura : Compsilura concinnata Meig. has been bred from the European corn borer {Pyrausta nubilalis Hiibn.) several times during the last few years. We con- sider it of little importance as a parasite of that species. To C. W. Johnson, the writers are indebted for the following: Thanaos brizo B. and L. April 19, 1920. Symmerista albifrons S. and A. (Rearings by E. T, Learned, Fall River, Mass.) Diprion simile Hartig. April 15, 1921. (Rearing record of M. P. Zappe, New Haven, Conn. ) EFFECT UPON NATIVE PARASITES What the final outcome of the introduction of Compsilura will be is for the future to decide. What has been accomplished by the *8 The species probably hibernates as a larva within its cocoon. 28 BULLETIN 1363, U. S. DEPARTMENT OF AGRICULTURE establishment of Compsilura, by its subsequent parasitism. upon native species, and by its present relation to the native parasites, is more obvious. | | ; As regards the majority of native parasites there is little to indi- cate anything detrimental to their welfare in the introduction of Compsilura, except an occasional scarcity of host material brought about by the successful attack of this insect. That this absence of host material is in itself of importance, inasmuch as it might.materi- ally change or upset the natural balance already existing, does not seem to be borne out by the records of the writers. It is true that there were no systematic collections of native larve prior to 1915 against which to check the larval collections of the last few years; there is, however, first-hand knowledge concerning serious outbreaks of native insects in this locality since 1907. The abundance of any insects for which the introduction of Compsilura might be held re- sponsible, because of its interference with the native parasites of the species in question, has not been recorded. On the other hand, infestations of insects which are due for their periodic outbreaks are, so far as known, not on the increase. That there is a consider- able amount of duplicate parasitism, there can be no doubt; and that this would be detrimental to one species or another, must also be true. Such an occurrence would take place in any case, however; and, although the presence of Compsilura probably adds to it, the results are not necessarily serious. It is possible that, because of the rapid larval development of Compsilura, it would crowd out forms which develop more slowly. This probably happens where | Compsilura and a native tachinid attack the host simultaneously. If, however, the native tachinid were in a stage of development more © advanced than that of Compsilura, the latter would in all probability — be the loser. There are few positive data on the rapidity of develop- © ment of many of the competing species, but it is believed that in © some of them the development is much slower than in Compsilura. What appears best to illustrate an occasion where there is a likeli- hood of Compsilura usurping the position of a native tachinid is | found in its relation to Tachina mella Walk. Here is a species far © less specialized than Compsilura, its reproductive habit being host- oviposition of a flat macrotype egg. Not only have the two species apparently similar hosts, but in nearly every instance where there © is competition the native tachinid is the one that suffers most. ‘That there has been a marked decrease in the number of 7. mella in the _gipsy-moth area since the establishment of Compsilura is probable. The parasite records of the writers show this, and there is corrobo- rative evidence as well. Forbush and Fernald, in 1896 (4, p. 388), | cited several instances of rearing mel/a from the gipsy moth. It is © rare that any mella are reared to-day, however, and in their aggre- © gate the larval collections of the gipsy moth are far greater than in the past. Forbush and Fernald (4, p. 385) call attention to the great number of tachinid eggs deposited upon gipsy-moth larve. It is possible, of course, that these eggs were not all laid by one species; but it is probable that a large percentage of them belonged to 7. medlla, as the records of rearing will show. During the past few years thousands of gipsy-moth larve have been sent to the laboratory and less than 1 per cent have tachinid eggs on them. Evidently one of HOST RELATIONS OF COMPSILURA CONCINNATA 29 two things has happened; éither me//a has found a host more favor- able than the gipsy moth or it has suffered a marked decrease in numbers. The latter view is the more logical. Compsilura is not entirely responsible for this condition, however, for there must be considered the prodigious waste of eggs by mella upon the gipsy moth. In the studies of Forbush and Fernald (4, p. 386) made dur- ing July, 1895, it was found that, whereas about 29 per cent of the gipsy-moth larve had tachinid eggs on them, these were in nearly every case moulted off before hatching. It is obvious that, if this futile attack by mel/a continued at the same rate for several years, there would necessarily be a great scarcity of the species. There are other instances besides that of Zachina mella in which the native tachinids meet with great competition, and a certain amount of duplicate parasitism results, in which the native species appear to be at a disadvantage. The tachinids Phorocera claripennis, Frontina frenchii, and Win- themia quadripustulata have a great variety of hosts, nearly all of which are also acceptable to Compsilura. Like Tachina mella they deposit eggs on the host larva and so are handicapped by the subcu- taneous larviposition of Compsilura. Probably P. claripennis fares the worst of these species, for with a single exception—Lophyrus lecontet Fitch—the host spectes are mutual. ‘There is evidence to indicate that not only does this species overwinter as a larva within its host pupa, but that it often successfully hibernates in the pu- parium. This habit is of the greatest importance, for it should be borne in mind that Compsilura depends upon certain lepidopterous pups for hibernation and that the number of overwintering indi- viduals is to that extent limited. The hibernating quarters of claripennis, on the other hand, are unlimited, and it can depend upon its abundance in the spring for successful competition. Frontina frenchu and Winthemia quadripustulata seem to be the least affected by the presence of Compsilura. As has been previously mentioned, frewchi finds an excellent overwintering host in the saturniids and meets there with little competition from Compsilura. There are many examples of the value of Samia cecropia as a winter host for frenchii. Fiske and Thompson (2) reared it in large num- bers and mention an instance in which 90 adults were reared from a single cocoon by C. H. T. Townsend. No other species met in the writer’s studies proves itself so generous a host. Of these native tachinids which possess the same general hosts as Compsilura, Winthemia quadripustulata seems best fitted for the contest. Not only does it more nearly approach Compsilura in the number of its hosts, but it also has a variety of others from which _ Compsilura has never been reared. It has, too, a decided advantage | over Compsilura, inasmuch as it, like Frontina frenchii, has several _ hosts which are capable of supporting a large number of individuals. _ Finally, it also has the advantage of hibernation as a full-grown _ larva or in the pupal state. Taken as a whole, the native larval collections reveal but few cases _ of tachinids peculiar to a single host. Among the species attacked by _Compsilura, there were found but 10 where there is a single compet- / ing tachinid with apparently no other host. Of these, the majority are of no particular host value to Compsilura. In one case only, that of Luvanessa antiopa L., is there any serious competition, and here 30 BULLETIN 1363, U. S. DEPARTMENT OF AGRICULTURE the native tachinid—Pelatachina pellucida Coq.—is well able to hold its own against Compsilura. A spring emergence at least two weeks in advance of Compsilura and an ability to hibernate in a puparium sufficiently guarantee its survival. EFFECT UPON HOST SPECIES Data concerning the relation of the native tachinids to their hosts prior to the introduction of Compsilura have been obtained through miscellaneous host records and published accounts of the insect. Data have also been obtained from two years of systematic collecting of native larve outside the Compsilura area, together with a few collections of larva made in a territory where Compsilura was hardly established. From comparative data thus obtained and from what can be sur- mised, it seems very clear that the addition of Compsilura to our fauna has been of great benefit. Not only has it accomplished the purpose for which it was introduced, namely, to act as a primary parasite on the larvee of the gipsy and brown-tail moths, but the rapidity of its dispersion has exceeded all expectations and it is now found established in an area independent of its primary hosts. It is in this area and especially along the outskirts of the moth infesta- tion that the presence of Compsilura means so much. The reasons are twofold: (1) Its attack upon a hght infestation of gipsy-moth larvee, such as would be found along the border of the infested area, would be, or at least has always been, attended with maximum re- sults, and the check exerted here is of the greatest importance; (2) possible dispersion of the gipsy-moth larve by the wind or otherwise in an unscouted area, and subsequent infestation, would result per- haps in complete annihilation by Compsilura. The establishment of Compsilura in this area is, of course, due to the alternate hosts upon which its existence is dependent. Of the many native hosts from which Compsilura has been reared, at least one-half are decidedly favorable for its development. The fact that Compsilura has, since its introduction into New England in. 1906, made its presence felt in no less than 92 species of native in- sects is in itself a manifestation of its efficiency. So thoroughly has this tachinid established itself in this region that it is now able to act as automatically as any native species whose mission is that of a con- trolling agent. Surely no better example of its ability to cope with the unexpected can be asked than its encounter with the satin moth (Stilpnotia salicis). Here an injurious insect, recently imported from Europe, in a single year appeared in astonishing numbers with- out the least semblance of control by native tachinids. It is ex- tremely doubtful if any of the native parasites would have proved effective had they had the field to themselves. Fortunately, however, | Compsilura had become acclimated, and the control exercised by it was remarkable. From certain last-stage larval collections, there have been obtained as high as 78 per cent parasitism. In their ag- gregate (last-stage larval collections) they will average at least 50 per cent parasitism. On the other hand, the sum total of.the native tachinids obtained from 20 collections is but 19 individuals, less than 2 per cent parasitism. Although this is perhaps one of the most spec- tacular instances of Compsilura’s potency, it is by no means excep- HOST RELATIONS OF COMPSILURA CONCINNATA Bil tional. The accidental introduction of other dangerous insect pests into the United States is probable, and it is possible that Compsilura may again serve as efficiently as in the case just cited. LITERATURE CITED (1) CoQqurmILLeTT, D. W. 1897. Revision of the Tachinidse of America north of Mexico. U. S. Dept. Agr., Div. Ent. Tech. Bul. 7, 156 pp. (2) CuLver, J. J. 1919. A study of Compsilura concinnata, an imported tachinid para- site of the gipsy moth and the brown-tail moth. U. S. Dept. Agr. Bul. 766, 27 pp., illus. (3) Fiske, W. F., and W. R. THOMPSON. 1909. Notes on the parasites of the Saturniidae. In Jour. Econ. Ent., vol. 2, pp. 450-460. (4) ForBusH, EH. H., and C. H. FERNALD. 1896. The gypsy moth. Porthetria dispar (ULinn.). 495 pp., illus. Boston. (Mass. Bd. Agr.) (5) HAwtey, I. M. 1918. Insects injurious to the hop in New York with special reference to the hop grub and the hop redbug. N. Y. Cornell Agr. Exp. Sta. Mem. 15, pp. 148-224, illus. (6) Howarp, L. O. 1897. A study in insect parasitism. U. S. Dept. Agr., Div. Ent. Tech. Bul. 5, 57 pp., illus. and W. F. FISKE. 1911. The importation into the United States of the parasites of the - gipsy moth and the brown-tail moth. U. S. Dept. Agr., Bur. Ent. Bul. 91, 344 pp., illus. (8) SmirH, H. HE. 1917. Notes on New England Tachinids, with the description of one new genus and two new species. In Psyche, vol. 24, pp. 54-58. (9) ToTrHiIty, J. D. 1922. The natural control of the fall webworm (Hyphantria cunea Drury) in Canada. Canada Dept. Agr. Bul. 3, n. s. (Ent. Bul. 19), 107 pp., illus. (7) ORGANIZATION OF THE UNITED STATES DEPARTMENT OF AGRICULTURE January 16, 1926 Secretary of Agriculture__..-...---------- W. M. JARDINE. Aissestant Secretatysctess 8 ee R. W. Dunuap. Director. of Screntific Works = <5 2-22 es Director of Regulatory Work ~_------------ WALTER G. CAMPBELL. PCCLOT Of Ti LLENS1ON W OTe "C. W. WARBURTON. Director ofl njonmation=—. x22 a ee NELSON ANTRIM CRAWFORD. Director of Personnel and Business Adminis- EV ALLOT it ee ee EE a Ro W. W. StocKBERGER. SOEGAIT ot Cee ee Sa Den eBar ame mes Samer UE R. W. WILLIAMS. PDT IEE a ET 2 a ne Re ee EIR ERE TER Cuarutes F,. Marvin, Chief. 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