238 DIPTERA OF NORTH AMERICA. [PART IV. 



Section V. ANISOMEEINA. 



Two submarginal cells (only one in Cladolipes') ; three, four, or five posterior 

 cells ; discal cell closed or open ; subcostal cross-vein near the tip of the 

 auxiliary vein, posterior to the origin of the second vein. Eyes glabrous. 

 The normal number of the antennal joints is six in the male and not more than 

 ten in the female. Tibiae with spurs at the tip ; empodia distinct ; ungues 

 generally smooth. 



This section is easily distinguished by the aberrant number of 

 antenna! joints. In other respects, the most numerous genus of 

 the family, Eriocera is exceedingly like the Limnophilina in its 

 venation and the structure of its male forceps. The species of 

 Eriocera and Penthoptera, have either five or four posterior 

 cells, a character which, in this section, seems to have no higher 

 importance than for the distinction of species. In Anisomera 

 and Cladolipes the posterior cells are reduced to the unusual 

 number of three ; to which, in the latter genus, is added the dis- 

 appearance of the first submarginal cell. 



These differences in the venation notwithstanding, strong links 

 of affinity unite these genera. The male has six-jointed antennae, 

 which, in some species, are much longer than those of the female, 

 sometimes more than twice the length of the body; while in other- 

 wise closely allied species the antennae of both sexes are short 

 and nearly of the same length. These modifications in the rela- 

 tive length of the antennae occur in the three principal genera of 

 this section, Anisomera, Penthoptera, and Eriocera. The female 

 antennae are short, and the structure of their apical portion is 

 such as to leave the number of the joints, composing it, some- 

 what uncertain, especially in dry specimens. On living female 

 specimens of Eriocera and Penthoptera I have distinctly counted 

 ten joints. 



The ovipositor of Anisomera has a peculiar structure ; the 

 valves are short and blunt, the upper ones much shorter than the 



