. Bulletin - United States National Museum. Science. 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 Asili
. Bulletin - United States National Museum. Science. 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 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 Hyl
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