292 JOURNAL OP ECONOMIC ENTOMOLOGY [Vol. 3 



parasites of the tussock moth always elect to pupate within the co- 

 coons of the host and among these there are some which do not 

 emerge until the following year. Exposed as they are to meteoro- 

 logical conditions, if their nymphal development continued to the 

 stage which it attains in Blephanpa scutellata before hibernation 

 commenced, they would stand small chance of passing the winter 

 successfully. 



The most remarkable example of the entrance of certain individuals 

 into hibernation, while others complete their development much more 

 rapidly, has been found in the case of Compsilura concinnata, which 

 is a several-brooded European parasite of the gipsy moth and other 

 hosts. In experiments which we have conducted with this species 

 and Hyphantria textor we have found that although some of the 

 parasites finished their larval development and emerged from the host 

 caterpillar within a short time, others attempted to hibernate as first 

 stage larvae within the pupa of the webworm. Less frequently, we 

 have found concinnata hibernating in the same stage in the over-win- 

 tering brown-tail moth caterpillars in somewhat the same manner as 

 does Zygohothria nidicola. Pantel, in his fine work, "Recherches 

 sur les Dipteres a larves entomobies, " has noted what is probably the 

 same thing with concinnata as a parasite of Pieris. He says: "In a 

 lot of chrysalids of Pieris collected in autumn, of which some were 

 unparasitized and others infested by Compsilura, there was a division ; 

 some butterflies emerged before the winter, their development follow- 

 ing the aestival type, but the eclosion of others w^as retarded until 

 spring. Now, the parasite behaves in exactly the same manner; some 

 individuals finish their larval development in some days and emerge 

 to pupate, while others will only emerge at the end of the winter or in 

 spring." Although the author does not indicate precisely that the 

 larva of concinnata hibernates in the first stage, there can be little 

 doubt, from remarks which he has made previously in the same paper, 

 that this is what occurs. Pantel attributes the singular behavior of 

 the parasite to seasonal influences, especially those of temperature. 

 It seems that this will scarcely explain the matter satisfactorily. To 

 begin with, it is difficult to imagine that conditions of temperature 

 should affect so markedly the length of the life cycle in certain in- 

 dividuals, without influencing that of others which are in precisely 

 the same conditions. The question also presents itself: what would 

 happen to the parasite should it elect to hibernate in the first larval 

 stage in a caterpillar which invariably developed to the adult stage 

 before the advent of winter? To avoid admitting the possibility of 

 such an occurrence one would be forced to the conclusion that certain, 



