1911] Aldrich — North American Species of Hydrophorus 53 



pleura with long yellowish or whitish hairs and no black bristle; mesopleura with 

 long hairs of the same color on the lower anterior part; metapleui-a just in front of 

 halter with a conspicuous tuft, which blends with a similar but shorter one on the 

 posterior upper part of the sternopleura; hal teres yellow with brown root; all the 

 coxse with dense yellow or whitish hair on front side, the front ones with also a 

 lateral tuft near base and no black bristles; front femur not much thickened, 

 on under side with two irregular rows of stiff bristles, and in the rather wide space 

 between the rows numerous irregularly placed short spinules; fore tibia with a row 

 of short spines of increasing length and erectness towards the tip, where the last 

 and largest spine is on a curved point of the tibia; in addition to this row there is on 

 the outer side from it (laterad) another row of larger, more scattered, slanting 

 spines, some ten in number; middle and hind femora slender, rather long, somewhat 

 bowed. Wings slightly infuscated, unspotted, of medium shape, strikingly dis- 

 tinguished by the shortness of the second longitudinal vein, which ends opposite 

 or a little before the hind crossvein (see figure); veins broadly yellow at base. 

 Abdomen bright green, pruinose on sides below, with thin white hairs all over, 

 longest and conspicuous on the sides of the basal joints; hj'popygium bulky but 

 short, bent under but not extending much forward. Length, 3.6 mm; of wing, 

 3.7 mm. 



Female. Considerably larger and brighter green than the male; third antennal 

 joint not drawn out into a point as in the male, yet all three of the antennal joints 

 may be called elongated; the face and the pale hairs of the body surface are yellow, the 

 the latter quite variable in depth of hue. Length, 5. 1 mm., of wing the same. 



Three males and seven females: Douglas Co., Kans. (Univ. 

 of Kans. Coll.); Brookings, S. D.; Pierre, S. D.; Boulder, Col. 



This species has such a wealth of specific characters that a 

 lengthy description seems almost unnecessary. The male has 

 a very remarkable appearance as it goes skating across the surface 

 of a pond, the long antennae pointing upward like a donkey's 

 ears. I well remember seeing it near Lawrence, Kansas, in June, 

 1893, though the males in my collection are not of my own cap- 

 ture, all being from the University of Kansas collection. The 

 females collected by me in South Dakota and Colorado were not 

 recognized at the time. It was Professor Melander's quick eye 

 that first noticed the peculiarity of the second vein, not men- 

 tioned by Loew. 



Hydrophorus canescens Wheeler (fig. 9). 



Male. Occiput coppery red, with only one pair of post verticals; postorbitals 

 about twelve on a side, ending opposite the neck; beard white, abundant, mixed 

 under the neck with some black bristles, which seem rather large and numerous; 

 cheek very narrow; front whitish pruinose, only in certain lights with a little cop- 

 pery reflection; face wholly white pollinose, palpi concolorous with white hairs, 

 antennae short, of ordinary form. Thorax coppery red or even crimson on most of 

 the dorsum, greenish about the edges, the acrostichals and all the dorsocentrais 



