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one parasite in eacii iiost larva attains to full development. 

 The larva of Steiniella callida Meig develops quite in the 

 same way in the larva of fJna populi. The parasite gene- 

 rally bores its way out of the host larva, but sometimes 

 the latter pupates before the parasite is fullgrown. Carcelia 

 gnava B. & B. deposits its eggs in July and August on 

 fullgrown larvæ of Malacosoma castrensis L. The host larva 

 always pupates before the parasite is fullgrown. The parasites 

 pupate in the pupa of the host and hibernate in this. From 

 2 to 5 parasites develop in each host, Tachina larvarum L. 

 has several generations during the year. A summer gene- 

 ration deposited its larvæ in July on fullgrown larvæ of 

 Malacosoma castrensis L. The host larva pupated with the 

 parasites in its body and the parasite larvæ pupated in the 

 lepidopterous pupa. The developed flies appeared in August. 

 An autumn generation was parasitic in both older and 

 younger larvæ of Spilosoma lubricipeda L. The parasite larvæ 

 all went out of the host larvæ and pupated in the ground; 

 most of the pupæ hibernated, but from a few the fly appea- 

 red iu October. I have found 2 to 7 larvæ in each host 

 larva; when a larger number of larvæ occur some of the 

 iniagos are generally dwarf-specimens, and the pupæ of 

 these differ from the pupæ of the normal specimens in several 

 respects (different colour, shape and sculpture). 



The larvæ of this species and that of the foregoing 

 may occur together in one ^fl/ocowwo-larva, and they may 

 develop side by side without difficulty. 



Of flies parasitic on imagines I have examined two 

 species. Viviana cinerea Zett. occurs in species of Carabus 

 and in Procrustes coriaceus. The larvæ are attached to a 

 trachea by a contraction of its chitin, which part forms a 

 funnel, enclosing the posterior end of the parasite larva (Fig. 

 8,9 k). On the outside of the chitinous funnel there is a 

 cell-coating which has grown out from the epithelium of the 



