6 DIPTERA OF NORTH AMERICA. 



Diamesa Meig., Corynoneura Winn., and Clunio Hal., which is 

 so remarkable by the habitation of its larva. The species of Cera- 

 topogon exhibit a good deal of varied organization. A division 

 into a number of smaller genera, which is indispensable, has been 

 attempted, but not executed in a satisfactory manner, and the 

 genera Labidomyia Steph., Culiocides Latr., Palpomyia Meig., 

 Sph^eromias Steph., and Prionomyia Steph. can be only consi- 

 dered at present as sub-genera of Ceratopogon. The genus Tha- 

 lassomyia Schin. has been separated from Chironomus. Also the 

 genus Macropeza Meig. must be united with the Chironomidce, 

 and Macquart is right in having done so in his "Dipteres exo- 

 tiques." The genus Orphnephila Hal. (= Thaumalea Ruthe = 

 Chenesia Macq.) differs from all the other Chironomidce by the 

 veins of the wings running without attenuation to, and the costal 

 vein being continued round, the posterior border. If we do not 

 establish a separate family for it, its proper place will be here, but 

 as an anomalous genus. 



The genera Chironomus, Tanypus, and Ceratopogon are largely 

 represented in N. A. ; the most interesting are the species of Cera- 

 topogon. Heteromyia Say belongs here. Of the remaining genera, 

 I have seen only one N. A. species, which belongs to the genus 

 Orphnephila, and does not seem to differ from 0. testacea Ruthe. 



Fam. III. CECIDOMYIDAE. 



Charact. — Ocelli often none. Thorax without transverse suture. Coxae 

 not elongated, femora not thickened, tibia? without spurs. Wings 

 having only few longitudinal veins. 



It is rather difficult to define sharply this most interesting family, 

 and consequently to characterize it exactly. It contains a very 

 large number of extremely delicate and elegant minute species, 

 remarkable by long and easily rubbed off hairs on the wings and 

 the other parts of the body. The limits between the families Ceci- 

 domyidce (Gall-gnats) and Mycetophilidce (Fungus-gnats) are not 

 very easily fixed, since Zygoneura Meig. shows a combination of 

 the characters of both; the coxa? being far less elongated and the 

 spurs of the tibiae far shorter than in any other genus of Myceto- 

 philidce; moreover, the antennae are moniliform with verticillate 

 hairs, as is frequently the case in the Cecidomyidce and never so 



