320 Professor Aldricli on the 



crooked near the middle. Hind metatarsi three-fourths the length 

 of the following joint, with a small but distinct bristle on the 

 underside. Wings a little smoky ; venation much as in Tachy 

 trechus (Loew, Mon. N. A. Dol., PI. III., 6) ; the third vein, how- 

 ever, is bent backward by a very gentle curve, beginning before 

 the middle of the wing ; the fourth vein runs in a straight line 

 past the cross-vein for a distance about equal to the length of that 

 vein, then bends forward in a gentle curve and is almost straight 

 for the rest of its course, but with a slight convexity forward. It 

 ends some distance before the apex, near the third vein. Costa 

 scarcely swollen before the end of the first vein. Fifth veia 

 attenuated near the end, obsolete before the border, 



9 . Face white poUinose of about the same width as in the 

 male, ending in a point below, which reaches fully to the lower edge 

 of the eyes. Palpi and proboscis rather small, brownish. First 

 joint of the antennae shorter than in the male, all the joints 

 blackened along the upper border. Middle tarsi simple ; hind 

 metatarsi but little shorter than the following joint. General 

 colour of thorax and abdomen deep blue, verging into green, 

 shining. 



Length 4-4-75 mm. ; of wing, 4*2 mm. 



Eleven males and eiglit females ; one label reads, 

 "Eichmond Valley, Forest. 1800 feet, December 31. On 

 stones along stream ; ^' another, " This species lights on 

 rocks in the beds of mountain streams above 1000 feet. 

 Very wary.^^ 



The green, blue, and silver colours of this species are 

 so changeable in dijfferent lights that they are difficult to 

 describe. There will be no difficulty in recognizing the- 

 insect. 



DiAPHOEUS. 



Meigen, Syst. Beschr., iv., 1824. 

 1. Diajphoriis opacus, Loew. 



This species was based by Loew on a single male 

 specimen from New York, and a female from Pennsyl- 

 vania was doubtfully referred to it. The length of these 

 specimens is 3 mm. I have numerous representatives 



