II. FAMILY PSYCHODID^E. 



Thickly haired, minute flies, in appearance moth-like. 

 Head small; ocelli wanting. Antennae as long as the 

 head and thorax together, bead-like ; thickly haired ; 

 composed of from twelve to sixteen joints; the two basal 

 joints shorter and short-cylindric. Proboscis usually 

 short; or more or less elongated (Ph Ic boto m u s) and 

 rigid; palpi incurved and hairy; composed of four joints 

 of nearly equal length. Thorax not very convex, with- 

 out transverse suture; scutelluni rounded. Abdomen 

 cylindrical, composed of from six to eight segments; 

 male genitalia prominent. Legs short, densely hairy; 

 claw r s small. Wings large, ovate or lanceolate in shape; 

 when at rest lying roof-like over the abdomen ; densely 

 covered with hair or tomentum, which also forms a fringe 

 around their margin ; the costal vein continuous about 

 the wing; veins strong, for the most part concealed be- 

 neath the hair ; venation formed almost wholly by longi- 

 tudinal veins; the anterior cross-vein is short and lies 

 near the root of the wing and is often difficult of discern- 

 ment ; the second longitudinal vein arises near the origin 

 of the first and is furcate. Fourth vein furcate; between 

 these two furcations there are usually two longitudinal 

 veins, the precise homologies of which are uncertain ; the 

 front one is often supposed to be an additional furcation 

 of the second ; or it may be a furcation of the third occur- 

 ring before the anterior cross-vein, a peculiar structure 

 found elsewhere in diptera only among the Tipulidae 

 (Ptychopterinee) . The vein just before the posterior furca- 

 tion terminates near the tip of the wing. Fifth and sixth 

 veins terminate in the border of the wing, as does also 



the seventh, which is, sometimes, very short. 



92 



