418 ENTOMOLOGICAL SOCIETY 



some of the facts that furnish the strongest direct proof thereof. 

 There is, as already stated, every gradation of parasitism in 

 insects, from the purely predaceous or inquilinous habit through 

 partial to complete parasitism. 



The Hymenoptera furnish no parasites upon warm-blooded 

 animals, while the Coleoptera furnish only the abnormal Plat- 

 ypsyllidce and Leptinidas, comprising but three mono-specific 

 genera. The affinities of the former with the Hydrobiini or 

 with Trichopterygidae, through such forms as Limulodes, have 

 been recognized by authorities ; while those of the latter with 

 some of the more abnormal Staphylinids, especially in the larva 

 state, is sufficiently apparent In the Diptera, however, the 

 QEstridas are strictly parasitic on such animals in the larva state, 

 with the adult state free. Now, the QEstridae are most nearly 

 related to the Muscidas, among which (Compsomyia, Lucilia, 

 Sarcophaga) a number of species have the habit of depositing 

 eggs or living larvas in some of the parts of the body of warm 

 blooded animals, either in wounds or natural openings. It is but 

 another step for such larvae to enter these cavities and become es 

 tablished there without producing immediate pathogenic condi 

 tions, and for this habit to become fixed and induce larval modi 

 fications more adapted to a parasitic life, and which affect chiefly 

 the dermal appendages, such as the hooks or anal spiracles, the 

 chief modifications being in the dermal spines, which are present 

 in an unspecialized form in all Muscid larvae. Doubtless the 

 more primitive or earliest developed of these GEstrid parasites are 

 those which infest the alimentary canal or nasal passages, since 

 they occur in localities most easily invaded, and in their arval 

 structure retain more nearly the normal Dipterous characters. 

 The species which invade the sub-cutaneous tissue exhibit a fur 

 ther step in the differentiation, while those larvae which live in 

 the walls of the stomach illustrate the highest differentiation, with 

 an accompanying greater modification in the character of the egg. 

 That this has been the actual method is supported by the onto- 

 genic facts, and the recent discoveries which I have called your 

 attention to. regarding the early larval history and structure of 

 Hypoderma lineata, acquire profound significance in this light, 

 for they point unmistakably to the common origin of Gastrophilus, 

 Hypoderma, etc., from an ancestral form which first acquired the 



