REARINGS AND DISSECTIONS OF TACHlNIDiE. Ill 



In our large outdoor cages we have been greatly struck with the 

 extreme docility of the ovipositing female tachinids. They can be 

 handled and caused to oviposit quite at the will of the operator in 

 most cases. 



AN IMPROVEMENT IN THE METHOD OF COLONIZING TACHINIDS. 



The extreme ease with which oviposition was secured in the cases 

 of T ncholyga grandiH and the Japanese and Eurojiean Tachinas in 

 the outdoor cages suggested the feasibility of an improvement in the 

 method of colonization hitherto ]:)racticed. lentil this season only the 

 flies themselves had been liberated, but recently the plan has been 

 adopted of colonizing caterpillars upon which the tachinids have been 

 induced to oviposit, in conjunction Avith the liberation of the flies. 

 Egg colonization, or the colonization of the caterpillars with the eggs 

 on them, is a step in advance of fly colonization, and thus gives 

 greater assurance of success in the establishment of the species. It 

 has proved very easy of accomplishment. Over 1,000 webworms 

 were colonized in July with eggs of the Japanese Tachinas on them. 

 Oviposition was secured in an outdoor cage by one assistant at the 

 rate of 200 to ;>00 eggs per day during favoral)le weather, these being 

 furnished by but little over a dozen ovipositing females. These flies 

 were afterwards liberated. The cage used is shown in figure 2(S. 



Early in August a new lot of Japanese Tachinas had become ready 

 for ()vii)osition in this cage, and one assistant in one day, working six 

 hours, secured 885 eggs from them on young caterpillars of Euproctis 

 rhri/s<))-i'h<ra from cold storage, one egg on a caterpillar. This lot of 

 eggs came from not over 20 ovipositing females. This is a very high 

 record of oviposition — almost an egg a minute — for it nuistbe remem- 

 bered that the cateri)illars had to be exposed, one at a time, to the flies. 

 These eggs, with others secured on other days, Avere colonized by 

 placing the caterpillars on new oak growth near the laboratory, 

 where defoliation by Porthetria d'n^ixw had occurred early in the 

 season. This second lot of Japanese flies was afterwards liberated, 

 over a thousan.d eggs having been secured from them on young 

 (finjsorrhoia^ and colonized. Some of the advantages of Qg^g col- 

 onization before liberation of the flies are the provision in the 

 outdoor cages of food and caterpillars for oviposition, and pro- 

 tection from enemies preceding and during a part of the ovipositing 

 period. Eurthermore, after fly colonization, if we find eggs of the 

 flies in question on caterpillars in the vicinity, we naturally consider 

 the establishment of the species to be more or less assured. If, how- 

 ever, we colonize the caterpillars themselves with the eggs of the flies 

 already on them, we have this assurance at the moment of coloniza- 

 tion, \Ahich nnist be considered a verv great advantage. 



