26O W. WESCHE. 



is characterized by a comparatively large head, flat thorax and 

 broad, flat abdomen; this includes the Rhyphidae, Simulidee, 

 Tabanidae and the Cyclorrhapha. The other section has a 

 small head, humped thorax, and a narrow, depressed abdomen; 

 this includes the Tipulidae, and the Brachycera, except the 

 Tabanidae, Leptidae, Therevidae and Bombylidae. The persist- 

 ence of these two well-marked forms is good evidence of my 

 argument, and, though it weakens the status of Williston's fifth 

 phylum it establishes even more strongly his first and second. 



ON THE CLASSIFICATION OF THE NEMOCERA. 



If the table of the mouthparts of the older families is examined 

 it will be seen that in only one family, the Cecidomyidae, is the 

 pharyngeal pump absent, but my specimens of this family are so 

 few in number that probably this observation has no value. I 

 feel confident that, with sufficient material, it will be demonstrated 

 in some genera, even though vestigial. But, I am sure that 

 Bibio, Dilophus and Chironomus do not have it, though it is 

 present in Scatopse and some Ceratopogones. Not only are the 

 Bibionidae singular in this respect, but the eye structure, the 

 limbs and bristle structure are all highly specialized. The usual 

 coloration of certain species is singular and as remarkable as 

 anything among Diptera, while the simpified venation and 

 modified mouthparts mark them off as the most specialized 

 family among the Nemocera. The only archaic characters re- 

 maining are the ocelli, the four-jointed palpi, and the long, 

 membranous labium of Dilophus, with the palpi inserted near its 

 end. In comparing the Chironomidae with the Bibionidse it will 

 be seen that the mouth is less specialized, since the stipites and 

 cardines are obvious and the mandibles are not fused, though 

 embedded in the ventral side, as in Bibio and Tipula; the eyes 

 are quite archaic in type, as is also the bristle and hair structure. 

 Though the Culicinse are highly specialized, the Corethrinse are 

 obviously older, and they possibly represent the continuance of 

 an ancestral form of the Chironomidae, as the venation is archaic 

 and the mouth retains the pharyngeal pump. 



These points show that the present arrangement of the families 

 of the Nemocera, though convenient, is not founded on a true 



