880 MAUD D. HAVILAND 



the host, always failed. The more prohable explanation seems 

 to be that the intention of the second hyperparasite is to ovi- 

 posit upon tlie A phi di us, but if by chance her ovipositor 

 comes in contact with the larva of the first, she is unable to 

 distinguish between it and the proper host, and places her egg 

 upon it. Certain observations support this view. For instance, 

 young larvae were never found thus parasitized, possibly 

 because they escaped discovery owing to their small size ; 

 and the mature larva of Lygocerus was never found to be 

 infected. There is very marked increase in the size in this 

 species between the early and late stages, and the latter is of 

 peculiar form with a dorsal conical appendage to the last 

 segment. The full-grown larva and the pupa are capable of 

 active movement, and jerk the abdomen violently when irritated. 

 It is possible that this action warns off the ovipositor of another 

 hyperparasite. I have observed only three instances where 

 Lygocerus was parasitized, and then always by its own 

 species. In two cases, larvae were observed on newly-trans- 

 formed pupae, and here, contrary to the usual rule, the egg 

 must have been placed on the larva when nearly full grown. 

 In the third case, an egg was found upon a younger larva, 

 whose power of movement was not yet developed. 



The Chalcid larvae, which are sluggish at all stages, are 

 more frequently attacked in their later instars by Lygocerus 

 and l\v other Chalcids. 



The incidence of mortality from epiparasitism is high in 

 the Cynipidae, since they invariably perish within the host 

 when the latter is attacked by an ectoparasite. Exceptionally, 

 a full-grown larva of C ha rips may be found epiparasitized 

 by a Chalcid or by Lygocerus, and in such cases it is 

 proba])le that the oviposition of the second hyperparasite 

 coincided with the emergence of the Cynipid from the host, 

 and before it had demolished the remains of the latter.^ 



' It should be pointed out that other forms not dealt with here are 

 involved in this bionomical complex. Thus Silvestri (" Contribuzioni alia 

 conoscenza biologica degli Imenotteri Parassiti ", '-Boll. Lab. Scuola 

 Agric. Portici ', vol. iii, 1909) has described the development of a Chalcid, 



