NORTH AMERICAN DIPTERA. 101 



proniineiit, about three-tenths width of head in S , of equal width, 

 face widening to half again as broad ; frontal bristles in two rows, 

 the outer row shorter and weaker, the two inner rows closely ap- 

 proximated and decussate, not descending below base of anteunte, 

 all about equal except two vertical bristles, which are much stronger 

 and directed backward ; no orbital bristles in % . Face nearly per- 

 pendicular, epistonia somewhat prominent ; facial depression short, 

 about two-fifths width of face, more or less oval in outline ; rather 

 shallow; facial ridges bare, except a few bristles above vibrissas not 

 entending halfway up, constricted well above oral margin ; sides of 

 face wide, bare ; cheeks less than one-fourth eye-hight, bare except 

 bristles on lower border and some hairs posteriorly ; vibrissie rather 

 short, but moderately stout, decussate, inserted high above oral mar- 

 gin. Eyes bare, descending below vibrissse, almost on a level with 

 oral margin. Antennae short, reaching little more than half way to 

 epistoma, inserted about on line drawn through middle of eyes, first 

 joint short, second elongate and bristly, third not much longer than 

 second ; arista not long, bare, thickened on basal third or more, o- 

 jointed, the second joint not elongate. Proboscis from one-fourth 

 shorter than to nearly as long as hight of head, rather slim, labella 

 developed; pal{)i slender, nearly filiform, curved. Thorax not wider 

 than head ; scutellum with a decussate apical pair of macrochjetse 

 reaching to base of second abdominal segment, a posterior lateral 

 pair reaching as far, and a shorter anterior lateral pair. Abdomen 

 elongate-oval, hardly as wide as thorax, first segment not shortened, 

 raacrochsetse moderately strong, only marginal, hypopygium of % 

 more or less exserted. Legs moderately long, not stout, not veiT 

 bristly; pulvilli and claws of S elongate. Wings longer than ab- 

 domen, without costal spine, third vein bristly at base; apical cell 

 opened well before tip of wing; fourth vein bent at nearly a right 

 angle, with a well-defined wrinkle at bend, apical cross-vein bent in; 

 hind cross-vein more or less sinuate, very oblique, nearer to bend of 

 fourth. Type, S. unica n. sp. 



^(arcoiiiaci'Oiiycliiu unica n. sp. %. — Eyes hrown, front silvery cine- 

 reous, frontal vitta appearinf; as a narrow black line, which widens behind en- 

 closing the ocelli; face, sides of face and cheeks silvery, with a dark reflection 

 in some lights; antennse and arista black, second antennal joint very bristly 

 and with a long bristle on front edge; proboscis black or brownish ; palpi riifons. 

 apical portion blackish, with some fine bristles on underside; occiput cinereous, 

 except black area below vertex, clothed with black liairs, fringed with short 

 black bristles. Thorax silvery, with three broad, quite well defined, black vittie 



TR.4.NS. AM. ENT. SOC. XIX. MAY, 189:2. 



