williston: apioceridvE. 107 



the variation does not offer even specific differences. This means, if it 

 means anything, that the family is comparatively recent geologically ; 

 the type is not in its decadence. On the other hand, let one compare 

 the wings of the four species of Apiocera figured herewith. Every 

 one would be placed in a different subfamily were they normal types 

 of the Asilidae ! One of the species (sp. ^.) even violates a promi- 

 nent family character ! That the absence of the anterior branch of 

 the third vein is not an accident, is evident from the fact that there 

 are two specimens before me quite alike. That such a remarkable 

 neurational character is not even generic in its value is shown by the 

 figure of another species (sp. c.'), likewise from Australia. In both 

 of these species the veins of the outer wing are very thin and weak. 

 The characters otherwise clearly prove that the two species are dis- 

 tinct. Here we have as a specific character a constant family charac- 

 ter of the Asilidae ! It is possible that these two species, differing as 

 they do from the stronger-veined forms, may eventually require generic 

 separation, but it is quite certain that the generic division cannot be 

 placed between the two species. 



What conclusions are we to deduce from such variations ? Quite 

 clearly to me they seem to show, as Brauer and I have already said, 

 that the Apioceridae represent a geologically decaying type, — a con-, 

 elusion borne out by their geographical distribution. I would repeat 

 the statement, with some changes, previously made by me, to which 

 Osten Sacken takes exception. The Apioceridae are most nearly re- 

 lated, genetically, to the Mydaidae and Nemistrinidae, less intimately 

 to the Asilidae and Therevidae. 



Mik has pointed out (13) that in none of the Apioceridae do we 

 find enlarged facets on the anterior portion of the eyes, so common 

 in the Asilidae. Osten Sacken will not admit that this character is of 

 much, if any, importance (23), but it seems to me to be entitled to 

 consideration, even though of minor value. Again, another character 

 that seems never to have been noticed, is the difference in the width 

 of the front in the two sexes, which is very marked in Apiocera, but is 

 not found in the Asilidae. It must mean that, genetically, Apiocera 

 is less remote from the holoptic type of male than are the Asilidae. 

 It is possible that there are true bristles on the front of some 

 species of Apiocera, but such are not present in the four species 

 known to me, and do not occur in the Chilian species, according to 

 Philippi; I believe that Osten Sacken is in error concerning this. 



Upon the whole, it seems plain to me, that to unite the Apioceridae 

 with the Asilidae is to do violence to real and distinctive structural 

 characters, which, carried but a little further, would require the union 

 of family after family, — that the step is retrogressive rather than 

 progressive. 



