ENTOMOLOGICAL SOc. OF BRITISH COLUMBIA, PROC. ( 1949) , VOL. 46, MAY 15, 1950

SOME PRELIMINARY OBSERVATIONS ON THE LIFE-HISTORY OF CUTEREBRA TENEBROSA COQUILLETI T. K . MOILLlET2 Livestock Insect Laboratory, Kamloops, B. C. On August 23, 1934, E. P. Venables, sufficiently developed it either died or Vernon, B. c., captured a large, dark waited a day or two before emerging. blue oestrid in a cabin at Sugar Lake, By October 31, 43 eggs had hatched, near Vernon, B. C. The writer has about half of these artificially. During since compared this fly with specimens the next two weeks about one-quarter of of warble fli es of various rodents, in the the remaining eggs hatched. Natural reference collection established at Kam­ hatching reached its peak about the sec­ loops by the late Eric H ea rI e, and iden­ ond week of November and practically tified it as a female of Cuterebra tene­ ceased by the middle of D ecember, when brosa Coq. During the next two days about 80 per cent of the eggs had the fly laid over 400 eggs in its card­ hatched. One larva, which emerged board container. and on September 10 naturally on December 3, lived until Mr. Venables sent the two largest egg December 13 at an average room tem­ masses, numbering 395 eggs in all. to perature of 60°F. and a relative humid­ the Kamloops laboratory in the hope ity as low as 15 per cent. that some rearing could be attempted. To determine whether or not the eggs The eggs had been laid in two patches would survive below-freezing tempera­ covering uneve nly about four or fiv e tures, the larger egg mass was placed out square inches . No particular care seems of doors between December 11 and 31, to have been taken in their arrangement during which period temperatures went by the female, except that each was se­ considerably below freezing. The min­ curely cemented, along its entire ventral imum recorded temperature was -5. 5°F. surface, to the cardboard and overlap­ on December 25. On December 31, ping of the eggs had been almost entirely eight of these eggs were opened at room avoided. The colour of eggs and adhe­ temperatures. At first the grubs were sive material is light yellow. As in most inactive, but after exposure to the oestrids, the egg is equipped with a "lid" warmth of a desk lamp for 30 minutes, which the larva forces open like a trap six showed normal activity which was door when ready to emerge. maintained for an hour, when they The eggs were kept in the laboratory were placed on a host. Eggs opened at at 70 a F. and about 25 per cent relative this time from the uncooled mass yield­ humidity, By September 20 no hatch­ ed active larvae. On February 8, 1935, ing had occurred, On September 27 five eggs from the previously cooled several eggs had hatched. Some half­ mass were opened. Two immediately dozen of the tiny maggots, 1 }4 mm. in yielded normal. active larvae, which length, were seen erect upon the card­ lived three days in an incubator at 75 °F. board and egg-shells, waving their and 70 per cent relative humidity. By heads to and fro. The larvae are very February 9, 90 per cent of all the eggs quick to stick to any object with which had hatched and 4 per cent had shriv­ they come in contact, and are able to elled. move about by looping, as both head Infestations: The following is an ac­ and tail appear to be sticky. The larva count of such rearings as have been is transparent except for series of black attempted up to the time of writing spines on each segment. When an egg ( 1935) . To infest an animal. the mag­ was opened with a needle it was ob­ gots were simply lifted with a needle served that the larva usually squirmed and placed on the hair of the back and' out, although in many cases when not sides of rats. Chloroform was used to

1 Contribution No. 2()34. Dhisioll of Entomology. quiet the rats because of the danger of Scienee Senice, Department of Agriculture. Ottawa, infection from rat bites. Canada. 2 Resigned 1936. Rat No. 1 (brown female, h.llf- 2 ENTOMOLOGICAL SOc. OF BRITISH COLUMBIA, PROC. (1949), VOL. 46, MAY 15, 1 950

grown). - This rat was infested on was re-infested on December 3 with six September 28 with 12 larvae from eggs artificiall y hatched maggots. It was mechanically opened. The animal was examined under chloroform on Decem­ very uneasy and scratched herself inces­ ber 20 and found to have two grubs, santly the same day. By October 5 the one behind each front leg. The rat was rat was hiccoughing continually and chloroformed on January 7 and the was little interested in food (oats). grub removed from under the left front Weakness and distress increased and by leg. That under the right shoulder October 14 the animal had gnawed half dropped on January 11, but wlas lost its tail away and was paralyzed in one and perished. In this case the grub, hind leg. On October 15 the rat was in unable because of a hard scab to leave its a coma all day and died about 5 p.m. host through the breathing hole, bored Necropsy was made at 11 p.m. Ema­ its way out head first about half an inch ciation was extreme; several matted in front of the original hole. patches of hair when pulled off revealed Rat No.5 (brown and white male). holes in the skin one mm. in diameter. -This rat was infested on December 4 Skinning revealed ten such holes, and with six grubs. By December 20, five eight grubs, varying in length from one­ grubs Were embedded, four in the back quarter to one-half of an inch, were and one on the right side of the breast. removed from the muscles of the legs, The rat died on December 31. and three back, and diaphragm. In some cases well-grown grubs were removed from they had pierced into the coelom. These the body, which was already badly de­ grubs do not form true cysts, as do ox composed in the areas of infestation. w:arbles, but lie between the layers of One grub was found in the tray, as well muscle. as the remains of another which had Rat No.2 (brown female. mature). been bitten out by the rat. The live -This rat was infested on October 16 grubs were placed in a jar of damp sand with four artificially hatched grubs. On for pupation. October 21 she was scratching herself Rat No.6 (white female. mature).­ and seemed in pain. On October 23 it This rat was infested on December 4 was apparent that one grub had estab­ with five grubs which hatched from eggs lished itself on the neck. just in front of opened the previous day. The rat was the left shoulder. On November 16 the examined under chloroform on Decem­ grub was nearly full-grown. and in an­ ber 20 and no infestation was found. ticipation of it's dropping the rat was Rat No. 7 (brown male, half­ isolated. The rat was found dead on grown). - This rat was infested on November J7 and the grub was cut out January 8 with four grubs artificially from under the skin and placed in a jar hatched. It was examined under chlor­ of damp earth. in which it immediately oform on January 20 and only a small buried itself. black spot was noted on the back. By Rat No.3 (white female. mature).­ January 30 it was noticeable that two This rat was infested on October 16 well-grown grubs were established in with four grubs, two naturally and two the back; these were nearly mature by artificially hatched. When the rat was February 8. examined under chloroform on October Rat No. 8 (brown female. mature). 31. no grubs were found. ' Three very -This rat was infested on January 8 small scabs on the neck may have been with three grubs artificially hatched caused either by fighting or by ineffec­ from the egg mass which had been sub­ tual entry of the maggots. jected to below-freezing temperatures. Rat No. 4 (white female. half­ The rat was examined under chloroform grown) .-This rat was infested on Oc­ on January 20; there was no sign of tober 18 with six grubs, three naturally infestation. and three artificially hatched. It was From these rearings no information examined u~der chloroform on October was secured on the duration of the pupal 31 and no grubs were found. The rat stage. One of several fairly well matured ENTOMOLOGICAL SOc. OF BRITISH C OLUMBIA. PROC. ( 1949). V OL. 4 6. MAY 15 , 1950 3 larvae taken by the writer at Nicola, months. A two-year cycle, however. August 25 , 1932, in a pack rat, was does not seem impossible when the via­ allowed to pupate in earth in the out­ bility of the eggs, even in cold weather. of-doors insectary at Kamioops, and is considered. It may have been because emerged in mid-August. 1933. of room temperatures, about 70 a F. , that Conclusions: Some of the foregoing so many eggs hatched within three observations suggest the following de­ months, although the humidity of the ductions regarding the habits of C. tene­ room, about 20 per cent, may have been brosa. an adverse factor. According to our It is usually assumed that the female records of grubs taken from rodents, fl y lays her eggs on the hair of the host flies of this group thrive best in localities animal. The extreme viability of the such as Nicola, Salmon Arm, and Ver­ egg and the longevity and motility of non, which have a relatively heavy the unfed maggot are specializations snowfall. They are rare at Kamloops. which would seem unnecessary were the The mortality of rats in the foregoing above assumption true. It seems, there­ experiments suggests that this fly may fore, more probable to suppose that the cause the death of small mammals in eggs are laid among the rocks, logs, nature in certain localities, although a nests, or burrows frequented by pack general infection may be induced by the rats, chipmunks, and ground squirrels, grubs less easily in mountain rats than the commonest hosts. In support of in those used in the laboratory. If they this, H . B. Leech has told the writer do constitute a factor in reducing popu­ that he captured in 1929 a female of lations of wild rodents, then they be­ this species in the mouth of a burrow come a factor in the control of wood of a ground squirrel or groundhog at ticks, and deserve further study. Vernon, B. C Acknowledgments. - The writer is The growth in the host is amazingl y indebted to E. P . Venables, Vernon, rapid, little over a month being required B. C, for the material for these experi­ for larval development. The pupal stage, on the other hand, is extraordi­ ments. Thanks are also due to H. B. narily long and may last a year, but in Leech, California Academy of Science, order for the life-cycle to be completed San Francisco, for his record, and to in a year, the average duration of this George J . Spencer, University of British stage cannot be more than 10 or 11 Columbia, for reading this manuscript.

ADDITIONAL NOTES ON THE LIFE-H ISTORY OF CUTEREBRA TENEBROSA COQUILLETI J. D. GREGSON Livestock Insec t Laboratory, Kamloops, B. C. At the 1935 meetings of the E ntomo­ of the remaining unhatched eggs yielded logical Society of British Columbia, T. active larvae when mechanically opened K. M oiIIiet read a paper entitled "Notes in February. Numbers of these larvae on the life- history of Cuterebra tene­ were used to infest rats, in which they brosa Coquillet." In that paper, which matured in about a month. Since none is being published concurrently with of these were foIIowed through their this one, he reported his observations on pupal period to emergence of adults, the some 400 eggs laid by a fly captured on following notes may prove of value in August 23, 1934. Larvae commenced further studies of this parasite. hatching from these eggs on September The material for these subsequent 27, reaching a peak in November. Some observations was provided by a batch of 1 Contribution No. 2n:i;;, Dhision of E1ltomology, 850 eggs deposited by a fly on July 26, Science S el'Yi c::e, Department of Agricult. ure. Ottawa, Canada. 1943. The first of these hatched on