INTRODUCTION 



ROBBER FLIES OF THE WORLD 



structures appear in some but not all members of this 

 subfamily and are of considerable phylogenetic 

 significance. 



The first of these structures is the modification of the 

 female ninth tergite into a pair of lateral, adjacent 

 plates, the acanthophorites, together with their accom- 

 panying hemicircle of spines ; this results in a character- 

 istic type of ovipositor, which is restricted to the higher 

 tribes of this subfamily only. Strictly analogous struc- 

 tures have appeared two or more times in the Asilinae, 



of asilids. If so they are differently constructed and of 

 independent origin. If these structures are not anal- 

 ogous, then these several families are closely related. 

 However, while these spines, when present in ther- 

 evids and mydaids, certainly do seem remarkably 

 similar to those of the Dasypogonini, I do not believe 

 them to be homologous. For so clearly are they absent 

 in some divisions of all three of these families that it 

 does not seem that such groups represent a loss of such 

 structures. 



Text-Figure 1. — The prosternum in 

 asilids and in Coenomyia Latreille; 

 stippled areas indicate membrane: A, 

 Coenomyia ferruginea Scopoli. B, Om- 

 matius sp. c, Andrenosoma xantho- 

 cnema Wiedemann, d, Nerax concin- 

 natus Williston. 



as in Proctacanthus Macquart, Philodicus Loew, but 

 located on the tenth segment. Certainly the spiny out- 

 growths on the ninth tergite of the Phellini and also in 

 some species of Chrysopogonini, both tribes of the lower 

 Dasypogoninae, seem to be analogous rather than 

 homologous, although there is a definite splitting of 

 this tergite in Psilozona Eicardo into distinct acan- 

 thophorites. 



These spines on the acanthophorites are a character 

 of special interest. There are similar structures on most 

 if not all female Therevidae, on many Mydaidae, and 

 on female Apioceratidae. Malloch (1928) has noted 

 such structures present in some species of the an- 

 thomyid Hylemya Desvoidy and in the bombyliid 

 genus Comptosia Macquart and the Anthracinae. Such 

 structures in these families may be analogous to those 



Also these spines and acanthophorites are lacking in 

 the lower Dasypogoninae, the Laphriinae, the Mega- 

 podinae, the Leptogastrinae, and all the Asilinae, and 

 in consequence I can not regard them as generalized 

 structures. Eather they have the appearance of being 

 adaptive specializations for the purpose of egg deposi- 

 tion and have appeared more than once in the Diptera. 

 I do not believe that they have arisen more than once 

 in the Dasypogoninae, except as crudely analogous 

 types in the lower groups as above cited. Melin 

 (1923) comments on the insertion of the egg in sand 

 by the asilid Lasiopogon Loew and Cyrtopogon Loew. 

 In common with several persons, I have followed the 

 steps in oviposition in this family. In western Arkan- 

 sas I have watched the asilid Diogmites Loew drill the 

 egg hole in hard soil, insert the abdomen, deposit the 



