112 MISCELLANEOUS PAPERS. 



NEW ALTERNATE HOSTS FOR INTRODUCED TACHINID FLIES. 



An important problem in the process of establishment of imported 

 summer-issning species of tachinicls is that new alternate hosts must be 

 found for them in this country. The caterpillars of PoHhetr'm dispar 

 and of Euprocth (■liryHorrlia'a have mostly pupated by midsunnner, 

 both here and abroad, and are thus not available as hosts after that 

 time. Therefore the late summer generations of these tachinids 

 develop in certain alternate hosts which occur in their native coun- 

 try. Those alternates are not present here, and new alternates 

 must be provided for them from our native species. Fortunately 

 tachinids are quite amenable to a change of host, (xratifying 

 results have been obtained in this direction. Tussock caterpillars 

 {Hemerocampa leucostigma S. & A.), have proved very acceptable 

 to Dexodes nigripes^ Conij^silura concinnata^ Tricholyga grand Is, 

 and other species, but they are not sufficiently abundant after mid- 

 summer to be of use for egg colonization on a large scale. Cater- 

 pillars of Datana^ BaK'darchia^ Euvanessa, Anis-of((, /Schisura, Melalo- 

 pha, and others have been found acceptable to the flies in most in- 

 stances, but likewise none of these is sufficiently abundant at the right 

 time. AVe were at first very much at a loss for suitable alternate host 

 caterj)illars in sufficitMit number. It was therefore most gratifying to 

 find that the newly hatched fall webworms {Ilyphaiitna ninea Dru.) 

 just coming on, a\ hich were abundant and easily obtained, were admir- 

 ably suited to the })urj)()se. Profuse oviposition was secured on these 

 from the Japanese Tachinas, and also from Tridudyga gr((ndiK, Tach- 

 hia l<ii-r(iriiiti , and others. The webworms, as soon as they had been 

 ovi})Osited on, wcnv put back in the webs in large colonies to insure 

 their prosperity. The fenuiles of Eupeletei'hi iTKupvicornh indus- 

 triously deposited their maggots on webworm-infested shoots, placed 

 with the flies inside the wire-screen receptacle shown in figure 29. 



To make success more certain in the ^g^^ colonization of the Japa- 

 nese and European Tachinas, oviposition was also secured on young 

 chrysorrhoea caterpillars that had been kept in cold storage until 

 about the 1st of August. Had it not been for the fact that a great 

 amount of new and tender oak foliage was available, where complete 

 defoliation by dispar had occurred during the early summer, these 

 chrysorrluva caterpillars could not have been used. The old and 

 matured leaves are not suited to the young caterpillars just out of the 

 nests, but the latter flourish on the new oak growth. 



Thus the question of alternate hosts in this country was satisfac- 

 torily answered, not only for purposes of ^^^ colonization, but also 

 for the needs of the liberated flies. The flies of Tricholyga grand is 

 and the first lot of flies of Japanese Tachina. all of which had, so to 

 speak, been trained to webworms through much oviposition on them, 

 were colonized in separate webworm localities. Thus it was certain 



