70 NORTH AMERICAN DIl'TERA. 



27. DOLICHOPODID.E. 



ISY I'HOF. J. M. ALDRICHU^--^ ' 



Small flies, never exceedinijf rniiu. in length, almost always 

 green in ground color, usually shining, more rarely dusted 

 with gray or brown, sometimes pure yellow or almost black. 

 As a family they are distinguished from their nearest allies 

 by the absence of the cross-vein between the discal and second 

 basal cells, these uniting to form a single cell. 



Head about as wide as the thorax (much wider only in 

 Psilopiuce), usually a little wider than high; the face bare, 

 very wide to very narrow, or the eyes contiguous below the 

 antennte ; , front generally widening rapidly above (in D'm- 

 phorus the eyes sometimes contiguous above), with bristles 

 on the vertex only. Posterior orbit with a well delined row 

 of short, erect bristles (toward the mouth indistinct in Hydro- 

 I)horinai and some other genera); ])roboscis fleshy, short, 

 retracted, rarely a little protruding ; antennne three-jointed, 

 inserted more or less above tlie middle of the eyes, the first 

 two joints never much elongated, the third commonly oval, 

 but in several genera lengthened ; arista dorsal, subapical, or 

 completely apical. Thorax hig h e r an ^r4en^ei"tlmTr-wtdej-w4th 

 regLiliudy arranged bristles on the do^rsum ; in some genera a 

 well-nuirked flattened or concave area before the scutcllum. 

 Abdomen tapejritng^ conical or a little compressed (in Hiidm- 

 j)lior\is and SceJlvs sometimes peculiarly small and retracted), 

 without noticeable bristles in most genera ; the -fiiale hypopy- 

 gium usually prominent, varying greatly in form, and in the 

 degree in which it is concealed in the abdomen. Coxif gen- 

 erally short, legs in most genera of medium length, sometimes 

 elongated, those of the male frequently developed into some 

 ornamental structure ; the front femora arg.thickened in a few 

 genera. Wings usually hyaline, yet often with dark mark- 

 ings, which may take the form of a definite pattern, or may 

 follow the veins indistinctlv. or mav be evenlv diffused ; in 



