354 PROCEEDINGS OF THE AMERICAN ACADEMY. 



within the abdomen of its host before the latter hibernates, and living 

 there through the winter. The females, owing to their parasitic life, 

 retain the larval form, while the free males are winged, not leading in 

 the adult stage a parasitic life, though passing their larval and pupal 

 stages in the body of their host, and are so unlike ordinary beetles as 

 to be referred by good authorities to a distinct order (Strepsiptera). 



The triungulin stage of these insects corresponds in general to the 

 form of the larval Staphylinidae and allied families, such as the Tene- 

 brionida?, which are active in their habits, running about and obtain- 

 ing their food in a haphazard way, often necessarily suffering long 

 fasts. In these external-feeding, less active coleopterous larva?, like 

 the phytophagous species, which have an uninterrupted supply of 

 nutritious food, we see that the body is thick and fleshy. So also in 

 the larvae of the Scarabaeidas, Ptinida?, and the wood-boring groups. 

 In internal feeders, like the larval weevils and Scolytid;c, which live 

 nearly motionless in seeds, fruits, and the sap-wood of plants and trees, 

 with a coustant supply of nourishing, often rich food, the eruciform 

 body is soft, thick, and more or less oval-cylindrieal. So it is with the 

 larva? of Hymenoptera, especially in the parasitic forms, and in the 

 ants, wasps, and bees, which are nearly if not quite motionless, at 

 least not walking about after their food. 



Now the change from the active triungulin stage to the series of secon- 

 dary nearly legless, sedentary, inactive stages is plainly enough due to 

 the change of station and to the change of food. From being an 

 independent, active, roving triungulin, the young insect becomes a 

 lodger or boarder, fed at the expense of its host, and the lack of 

 bodily exertion, coupled with the presence of more liquid food than 

 is actually needed for its bare existence, at once induces rotundity 

 of body and a loss of power in the limbs, followed by their partial or 

 total atrophy. 



That this process of degeneration may even occur in one and the 

 same stage of larval existence is very well illustrated by what we 

 know of the life history of the wasp parasite of Europe, Rhipiphorus 

 paradoxus. Thanks to the very careful and patient observations of 

 Dr. T. A. Chapman, we have a nearly complete life history of this 

 beetle, the representative of a family in many respects connecting the 

 Meloidoe and Stylopidae.* Where Rhipiphorus lays her eggs is un- 

 file larva, contrary to the suggestion of Mr. Kelly." Class. Insects, II. 297. 

 This is all we know about the supernumerary larval stages. 



* Some Fncts towards a Life History of Rhipiphorus paradoxus. Annals and 

 Magazine of Natural History for October, 1870. 



