PSYCHOBIDjB. 27 



and hairy ; composed of four joints of nearly equal length. 

 Thorax not very convex, without transverse suture; scu- 

 tellum rounded. Abdomen cylindrical, composed of from 

 six to eight joints; male genitalia prominent. Legs very 

 short, densely hairy ; claws small ; pulvilli rudimentary. 

 Wings large, ovate in shape ; when at rest lying roof-shaped 

 over the abdomen; densely covered with long hairs or tomen- 

 tum, which also forms a fringe around their margin ; the 

 costal vein continuous around the wing; veins strong, for 

 the most part concealed beneath the hair ; neuration 

 formed almost wholly by longitudinal veins; the anterior 

 cross-vein is very short, and lies very near the root of the 

 wing ; auxiliary vein weak or indistinct ; first longitudinal 

 vein very near the costa ; second longitudinal vein arises very 

 near the origin of the first, and is usually twice forked, that 

 is, the upper branch of the furcation is again furcate ; third 

 vein simple, terminating at or beyond the tip of the wing ; 

 fourth vein furcate ; fifth and sixth terminating in the border 

 of the wing ; seventh vein usually distinct, reaching to the 

 margin of the wing, sometimes wanting. 



The members of this family are often very minute, rarely 

 exceeding the length of four millimeters ; they occur in shady 

 places, on windows, about outhouses, and will be readily recog- 

 nized from their peculiar moth-like appearance ; they run 

 about nimbly, but their flight is weak. The larvae live in 

 rotting vegetable material, or in water, especially stagnant 

 water; they are cylindrical, with the posterior end termi- 

 nating in a short, usually firmly chitinized, stigmatic tube ; 

 the maxillae are imperfectly developed, there are eye-spots on 

 the head, and the segment behind the head are without feet. 

 The pupae are inactive, with two long tube-like, anterior 

 stigmata. 



But two genera are known to occur in North America; 

 Psychoda and Pericoma, which may be distinguished from 

 each other by the termination of the third vein of the wing, 



