932 CHARLES PAUL ALEXANDER 



Genus Trimicra Osten Sacken (Gr. three + small) 



1861 Trimicra O. S. Proc. Acad. Nat. Sci. Phila., p. 290. 



Trimicra is a small genus of crane-flies, including about fifteen described 

 species found in most parts of the world, almost all being forms of moderate 

 size and obscure coloration. These various species bear a close resem- 

 blance to one another and are hard to distinguish specifically. 



Bergroth and other European writers consider the genus Trimicra as 

 being the same as Psiloconopa Zetterstedt, but at this time the writer 

 is not entirely willing to accept this view. 



Beling (1879:48) described what he took to be the larva of one of 

 these flies, and in his key to the larvae of crane-flies (1886:206) he 

 included it in close proximity to the Pediciini. As mentioned elsewhere 

 in this paper, it is highly probable that Beling described a pediciine larva, 

 but by an accident had larvae of Trimicra in his breeding jars, the latter 

 larvae emerging first and confusing the author. 



Gerbig (1913:161-163) describes the real larva of Trimicra pilipes 

 (Fabr.), the best-known species of the genus. It is found along the 

 margins of flowing streams with muddy banks. It is a dark-colored 

 larva, about 15 millimeters in length and about 2 millimeters in 

 diameter. The skin of the body is similar to that of the larvae in the 

 typical subgenus of the genus Limnophila, being covered with chitinous, 

 hairlike projections, which in Trimicra are longest on the dorsal surface of 

 the body. On each segment there are solitary elongate bristles, above and 

 below each of which is a gland. The spiracular disk (Plate LXXIII, 395) 

 is surrounded by five nearly equal lobes, which have the inner faces 

 marked with equal blackened, chitinized areas. On the lateral margins 

 of each lobe, but occupying only the distal part of the lobe and not con- 

 tinuous around the disk, is a fringe of moderately long hairs. At the 

 tip of each ventral lobe are two bristles, and at the tip of each lateral 

 lobe is a single bristle, these being inserted outside the line of hairs and 

 surrounded by a bright circular area. The ventral sensory bristles found 

 in some crane-fly larvae (as Tipula variipennis) are lacking. At the 

 base of the lateral lobes are the spiracles, which are generally similar to 

 those in the subgenus Limnophila. Gerbig discusses in detail the structure 

 of the spiracles, the felt chamber, and the musculation of this region 

 of the body. 



