492 



case of Dinocampus terminatus. By irritating a Coccinellid, 

 the natural host of Dinocampus so that it exuded fluid from 

 its joints and applying this juice to Collops he was able to 

 secure oviposition in Collops but without securing development 

 within that host. I have been able to secure a similar result 

 in another case in which the ncM' host was suitable for the 

 development of the parasite. 



In April, 1915, while in Capetown, I found an undeter- 

 mined species of the Ichneumonid genus Alloiypa breeding in 

 a Sarcopliaga the larva of which feeds in human excrement. In 

 extensive breedings of Diptera there I did not secure it under 

 natural conditions from any other host. The adult female lies 

 in wait for the larva when it emerges full-grown to enter the 

 soil for pupation and attacks it with great fury and oviposits 

 in its body, the adult parasite emerging from the puparium 

 which is normally developed. On studying the species in 

 captivity, I found that, while Sarcopliaga larvae introduced into 

 a tube containing the parasites stirred them up into a state of 

 the greatest excitement in which they would attack them with 

 great fury, charging them with the abdomen projected forward 

 between their legs, climbing upon the body of the larvae and 

 stinging them indiscriminately on the first part encountered 

 and even attempted to sting the glass of the tube, any other 

 muscid larvae such as that of Miisca lusoria living in cow dung 

 would be received with complete indifference, hardly moving 

 away to avoid them as they wandered about in the tube. But 

 if to such a tube containing the Allotypa parasites and the 

 Musca lusoria larva even a single larva of Sarcopliaga (of 

 any of the species) was introduced the parasites would be 

 almost as excited as if all the larvae were those of Sarcopliaga 

 and in this way the parasite was induced to oviposit in the 

 Musca lusoria larva and from these larvae adults of the para- 

 site were obtained, from a host which could never be utilized 

 in nature since the olfactory stimulus from the Sarcopliaga 

 could hardly in nature ever be associated with the Musca lu- 

 soria larva. This limitation by an olfactory factor causes a 



