14 DIPTERA OF NORTH AMERICA. 



Meig. (= Messala Curt.), HETEROTRICHA Loew, DIANEPSIA Loew, 

 SCIARA Fabr., and the genus DIOMONUS Walk., which is unknown 

 to me. I have not mentioned the genus SYNAPHA- Meig. , because 

 it seems to have been founded on an individual of a species of Leja, 

 which possessed an irregularly formed neuration ; at least as far 

 as I know, no second specimen of Synapha has been captured 

 since Meigen's time, while a similar anomaly of neuration of the 

 wings has been observed several times in other Diptera. 



Our knowledge of N. A. Mycetophilidceis exceedingly incomplete. 

 I have seen species of the genera MYCETOPHILA, BOLETINA, Scio- 

 PHILA, TETRAGONEURA, PLESIASTINA, DITOMYIA, PLATYURA, MA- 

 CROCERA, BOLITOPHILA, and SCIARA. Besides these, the existence 

 of CEROPLATUS seems to be certain, and the genus DIOMONUS, 

 which I bave never seen, is founded on a N". A. species. 



FAM. YIIL SIMULIDAE. 



Charact. Ocelli none. Thorax without transverse suture. Wings with 

 very short hair only visible under a very high magnifying power ; 

 legs short, tibiae without spurs ; posterior tibire and first joint of 

 the hind tarsi dilated. 



The present family comprises only the genus SIMULIUM Latr., 

 rich in species and which cannot be placed in any other family. It 

 does not seem to be less rich in species in N. A. than in Europe. 



FAM. IX. BIBIONIDAE. 



Charact. Ocelli three. Thorax without transverse suture ; prothorax 

 much developed. Wings without discal cell; coxae not prolonged ; 

 empodium proportionally long, whereas the pulvilli are wanting in 

 some of the genera. 



The family of Bibionidce is divided into two sections sharply 

 separated from each other, and which it would be proper to con- 

 sider as distinct families. In the SCATOPSINA, which form the first 

 section, the palpi are very short, the pulvilli wanting, the tibias 

 without spurs ; the genera belonging to them are : SCATOPSE 

 Geoff}'., ASPISTES Meig., ARTHRIA Kirby. To the second section, 



the BIBIONINA, belong: DILOPHTJS Meig., BIBIO Geoffr., PENTHE- 



