166 DIPTERA OF NORTH AMERICA. [PART IV. 



comparatively narrow. The venation has nothing abnormal, and 

 strikes at once by the straight course and the parallelism of the 

 veins, ending in the apex of the wing, between the latter portion 

 of the first longitudinal vein and the second posterior cell ; hence 

 the rather long first and second submarginal and first posterior 

 cells have parallel sides and are narrow and linear. Discal cell 

 subtriangular ; the great cross-vein a little anterior to it ; the 

 auxiliary vein ends opposite the marginal cross-vein ; the first 

 longitudinal vein some distance beyond it; the origin of the 

 second longitudinal vein is some distance before the middle of 

 the anterior margin ; the prsefurca is straight, and its curvature 

 near its origin is none or almost none ; petiole of the first sub- 

 marginal cell shorter than the great cross-vein ; the marginal 

 cross-vein is a trifle beyond the inner end of the first submarginal 

 cell; the sixth as well as the seventh longitudinal veins are nearly 

 straight. The stigma is almost imperceptible, hardly marked at 

 all. The venation of the European T. pilipes and the North 

 American T. anomala are exactly alike. 



Trimicra forms a natural transition between Erioptera and 

 Chionea on one side and Symplecta on the other. The position 

 of its subcostal cross-vein and of the origin of the second longi- 

 tudinal vein proves its relationship to Erioptera. Symplecta 

 possesses the same characters, somewhat weakened however ; its 

 prsefurca is more distinctly arcuated near its origin, and this 

 origin is somewhat less near the basis of the wing ; moreover it 

 has, like Trimicra, the great cross-vein somewhat anterior to the 

 discal cell. But although the sinuated course of the seventh 

 longitudinal vein, and the structure of the male genitals suffi- 

 ciently distinguishes Symplecta, both genera are very closely 

 allied. The European species, Symplecta stictica and similis, 

 are very like Trimicra in outward appearance, but I have had 

 no opportunity to examine the structure of their forceps. Among 

 the Eriopterae with short hairs along the veins some might per- 

 haps be mistaken for Trimicras. But the pubescence of the 

 wing-veins of this genus is much more minute, hardly per- 

 ceptible ; the seventh longitudinal vein runs straight to the pos- 

 terior margin, the axillary cell being broadest near the margin ; 

 the inner ends of the second and third posterior cells are in one 

 line, making it appear doubtful which of the branches of the 

 fourth longitudinal vein is furcate. The Eriopterae of the section 



