278 DirXERA OF NORTH AMERICA. [PART IV. 



darker at both ends than in the middle. In other respects the 

 resemblance between this specimen and U. paupera is very great. 



Gen. XXXVIII. DICRAIVOTA. 



Two snbmarginal cells ; four or five posterior cells ; discal cell open 

 (adventitiously closed in abnormal specimens) ; there are two marginal 

 cross-veins between the first and the second longitudinal veins ; the sub- 

 costal cross-vein is a considerable distance before the oi-igin of the second 

 longitudinalvdn (Tab. II, fig. 16). Tibiae with small but distinct spurs 

 at the tip ; empodia distinct. Eyes pubescent ; distinct gibbosity on the 

 front, behind the antenuse ; the latter 13-jointed. 



The eyes are remote, being separated on the upper side of the 

 head by a rather broad front ; the latter shows in fresh specimens 

 a distinct gibbosity behind the antennae,* which seems to shrink 

 in dry specimens. Rostrum and proboscis short ; palpi short. 

 Antennae 13-jointed ; the structure of those of the European 

 species is thus characterized by Mr. Haliday (Walker, Ins. Brit. 

 Diptera, Yol. Ill, p. 307) : " Male : Antennte a little longer than 

 the thorax ; third and following joints oval. Fern : Antennae 

 submoniliform, a little shorter than the thorax." In the North 

 American D. rivularis the antennaj of both sexes are very similar 

 in structure ; if bent backwards, they would not reach much beyond 

 the collare ; first joint subcylindrical, the second short, cyathiform, 

 the third obconical, attenuated at the basis ; the following joints 

 subglobular, gradually becoming narrovi^er towards the tip ; the 

 flagellum is clothed with some short, scattered hairs, which can 

 hardly be called verticils, and I do not perceive the delicate 

 pubescence, often occurring in males of Tipulidse. 



The antennae of the male of D. eucera are of an entirely differ- 

 ent structure ; tjicy are twice the length of head and thorax taken 

 together; the flagellum is clothed with a dense, delicate pubes- 

 cence, without any verticils ; the joints are cylindrical, elongated, 

 of nearly equal length, except the last, which is shorter. The 

 head is rather closely applied to the well-developed collare ; the 

 thoracic suture is well marked. The feet are long, moderately 

 strong ; the spurs at the tip of the tibire, although short, are very 

 distinct. The wings have four posterior cells in two European 



' This statement is repeated from Proc. Acad. Nat. Sci. Philad. 1859, 

 p. 249, as I have not had any opportunity of seeing fresh specimens since. 



