I1YDR0PH0RUS. 215 



the fore femora as usual, thickened towards the basis, on their 

 under side with two rows of thorn-like bristles, the inner row of 

 which reaches as far as their tip, while the exterior one stops 

 already on the middle of the femora. Tibiae dark-green, the fore- 

 most uniformly fringed, upon their under side, with very short 

 thorn-like bristles. Tarsi black. Cilia of the teguhe fallowish- 

 yellow. Halteres with a dusky-yellowish peduncle, and with 

 blackened knob. "Wings very long, tinged with gray, not darker 

 towards the anterior margin, with black veins up to the extreme 

 root ; the end of the third longitudinal vein somewhat approaches 

 the fourth, so that these veins converge distinctly towards their 

 ends ; upon the posterior transverse vein and upon the convexity, 

 which the last segment of the fourth longitudinal veins crosses, 

 there is a somewhat more gray spot, which is almost invisible to 

 the naked eye. 



Hob. Pennsylvania, District of Columbia. (Osten-Sacken.) 

 Observation. — It is difficult to determine, whether H. pirata is 

 not one of those four species of Hydrophones which Mr. Walker 

 has described as species of Medeterus. They agree in a good many 

 respects not only among themselves, but also with H. pirata, 

 while each of them exhibits also some distinguishing feature. H. 

 viridifios must be much more green, according to Mr. Walker's 

 statements, than H. pirata; besides, the cilia of the inferior orbit 

 of the former one are white, while those of the latter are yellow; 

 moreover, its abdomen is conical and longer than the thorax, an 

 entirely uncommon character for a female of Hydrophorus, and 

 making it almost doubtful whether it really belongs to this genus ; 

 finally the veins of the wings are said to be brownish-yellow near 

 the root of the wing ; these discrepancies are altogether too great 

 to justify the supposition that H. pirata can be identical with 

 viridifios Walker. The face of Walker's female of H. glaber is 

 said to be covered with golden-yellow dust, the abdomen on the 

 upper side clothed with brownish-yellow hairs, the femora rather 

 stout and the halteres brownish-yellow. These differences are 

 likewise too important to admit the identity of H. pirata with H. 

 glaber. The face of Walker's female of H. chrysologus is said to 

 be also covered with golden-yellow dust ; the wings are said to be 

 brown along the anterior margin, and to measure only three lines 

 in expanse, whereas they measure six lines in H. pirata. Under 

 such circumstances the identity of these species is out of question. 



