262 W. WESCHE. 



difficult to say whether the Culicidae or the Chironomidae should 

 have the precedence. The former are entitled to it on the 

 venation (an obviously old form, possibly ancestral) and on the 

 mouth, though I have a Ceratopogon in my cabinet with pharyn- 

 geal pump and broad-bladed maxillae and mandibles, which is 

 more primitive in type than the armature of Culex. But this 

 is exceptional, the majority of the Ceratopogones being without 

 mandibles and having the laciniae of the maxillae of a simpler 

 type. The archaic type of eye structure is matched by Corethra 

 and the absence of a pharyngeal pump in so many genera, whereas 

 it is always present in the Culicidae, decides in their favor. 



The Blepharoceridae follow, and the Chironomidae after. I 

 have already given my reasons for placing the Bibionidae last. 



Williston, in the true spirit of a paleontologist, has speculated 

 on the primitive dipteron, and has given in words a reconstruction 

 of a hypothetical form (p. 331, 2), as follows: "The primitive 

 dipteron must have had eight fully developed longitudinal 

 veins (including the auxiliary vein) with the second, third, 

 fourth and fifth furcate, and a complete discal cell. The head 

 was rather small, with the compound eyes separated equally by 

 the front in both sexes. The ocelli were functional, and the 

 maxillary palpi had four freely articulated joints; the labial 

 palpi had probably already disappeared, though Wesche thinks 

 differently- There were at least thirty-nine antennal joints 

 in the male. The prothorax, mesothorax and metathorax 

 were imperfectly fused, and the metanotum was visible from 

 above. The abdomen had nine functional segments; the body 

 was without differentiated bristles; and the tarsi had membranous 

 pulvilli and empodia. The primitive flies were of moderate or 

 small size, and probably crepuscular in habit, or at least denizens 

 of shady forests." 



Williston goes on to say that of modern Diptera the Tipulidae 

 approach most closely this hypothetical ancestor, principally 

 in the venation, and remarks that they have become specialized 

 by the almost complete loss of the ocelli, increase in size, and the 

 loss of the pulvil-H. He places the Rhyphidae next in rank to the 

 Tipulidae. It seems to me, however, by his own diagnosis, that 

 the Rhyphidae are more primitive than the Tipulidae. They 



