204 



UNITED STATES NATIONAL MUSEUM BULLETIN 224 



PART 1 



Head, anterior aspect : The face below the antenna is 

 rather narrow and divergent below, the vertex less ex- 

 panded. Subepistomal area short, nearly horizontal, 

 deeply concave and bare. The face is pubescent with 

 dense, matted pile and bristles which begin at the an- 

 tenna; the bristles are concentrated below and extended 

 down along the lateral margin to the epistoma but in 

 some species they may be confined to a single transverse 

 row of very stout bristles. The front is long, vertical 

 and plane, pubescent, almost without pile. Vertex but 

 little excavated, the ocellarium large and broad, rather 

 high, with steep sides and bearing across the middle 6 

 pairs of slender bristly hairs or a dense tuft of similar 

 hair, with a pair of slender bristles and 1 or 2 additional 

 pairs between the posterior ocelli. The anterior ocel- 

 lus is exceptionally large; lateral margins of the vertex 

 with a tuft of dense pile in many species, perhaps in all. 

 Anterior eye facets exceptionally strongly enlarged. 



Thorax : The thorax is pollinose ; the pile of the meso- 

 notum is scanty but rather long, suberect, and slightly 

 bristly; there is a row of acrostical pile which is quite 

 distinct, a row of long, slender, dorsocentral bristles, 

 which opposite the humerus tends to expand into a 

 cluster; posteriorly these are sometimes reduced to very 

 short hairs, but may continue in their same length. 

 Humerus with 2 or 3 distinct bristles and with the fol- 

 lowing complement of quite long and rather stout, lat- 

 eral bristles : 2 to 3 humeral, 2 posthumeral bristles set 

 far from the lateral margin and sometimes absent, 3 

 notopleural in an oblique row, reduced to 2 sometimes, 1 

 to 3 supraalar, 2 postalar, with at least 6 to 8 pairs of 

 long, stout, scutellar bristles. Scutellum flattened 

 towards the base, gently convex distally densely pu- 

 bescent, without pile. Propleuron with exceptionally 

 dense tufts of long, coarse pile ventrally and on the 

 posterolateral pronotum; the dorsal pronotum has a 

 band of less numerous fine hairs ; bristles absent. Meso- 

 pleuron without pile or bristles. The sternopleuron has 

 a few scattered hairs 2 or 3 in the middle dorsally 

 and a tuft anteriorly. Pteropleuron and hypopleuron 

 apilose, the latter with a patch of pubescence. Meta- 

 pleuron with a wide band of long, slender bristles and 

 bristly hairs closely adjacent. Lateral slopes of the 

 metanotum micropubescent only, the posterior border 

 of the lateral metasternum and the chitinized ventral 

 metasternum with abundant, long pile. Postmetacoxal 

 area membranous; tegula pubescent only. Prosternum 

 dissociated. 



Legs: The femora are stout but only moderately 

 thickened or swollen; the hind pair is considerably 

 longer than the middle pair. Pile of the femora long, 

 coarse, and more or less appressed. The following 

 complement of bristles present in the type of genus: 

 15 dorsolateral, part of which represent doubled ele- 

 ments and those on the outer half are more conspicuous 

 and there are also 5 or 6 less conspicuous lateral bristles 

 and a ventromedial fringe of 8 to 10 bristly hairs. 

 There are also 2 slender, subapical bristles dorsomedi- 



ally with other shorter ones at the apex. Hind tibia 

 show 5 or 6 dorsomedial, a like number of dorsolateral 

 bristles, 4 or 5 lateral, and 5 stout, conspicuous ven- 

 trolateral bristles, besides 4 equally conspicuous ven- 

 tromedial bristles. Middle femur with 4 or 5 anterior 

 bristles, most of them slender and short, with a like 

 number of ventral bristles, of which 2 found near the 

 middle are comparatively stout. This tibia shows con- 

 spicuous bristles, long, oblique, stout, pale and slightly 

 attenuate. There are 6 anterodorsal, a like number of 

 slender posterodorsal, and 7 long posterior bristles, and 

 at least 5 posteroventral bristles. Anterior femur with 

 a band of long, shaggy, bristly hair posteriorly ; this 

 tibia has 4 short, anterodorsal, a like number of 

 slightly long, posterodorsal, 4 long posterior bristles 

 and the same number of ventral bristles. The anterior 

 tibia ends without spine; all the tarsi slender; all the 

 anterior tarsal segments elongate, their bristles promi- 

 nent. Tarsi end in long, slender, sharp, slightly curved 

 claws, no pulvilli, and with a long, slender, empodium. 



Wings: The wings are hyaline; marginal cell widely 

 open, the first and second posterior cells open in their 

 maximal width, the fourth slightly narrowed, the anal 

 cell narrowly open or closed in the margin. The upper 

 end vein of the discal cell is shorter than the oblique, 

 lower vein ; the anterior crossvein enters the discal cell 

 beyond the middle; the middle end vein of the second 

 basal cell is a third the length of the upper vein ; the 

 alula is quite as wide as the costal cell, the ambient 

 vein complete. 



Abdomen: The abdomen is broad basally, as wide 

 as the mesonotum, comparatively short and strongly 

 tapered with a tendency to be flattened on the basal 

 tergites. Pile of the abdomen scanty, coarse, compara- 

 tively short but longer on the sides of the first three 

 tergites and in the females directed backward on the 

 terminal segments. Males with eight tergites, the 

 eighth from a third to half as long as the seventh and 

 the seventh slightly shorter than the sixth, all tergites 

 progressively shortened beyond the first. Females with 

 eight tergites, the eighth is two-thirds as long as the 

 seventh and sometimes much shorter. Male termi- 

 nal ia rotate a fourth to the left, short, with the epan- 

 drium cleft to base, but apposed on the basal half 

 leaving the distal portion flared outwardly as flat, 

 rounded lobes. Gonopod small, cylindrical but dis- 

 tinct. Hypandrium present and short, leaving the 

 cavity open and exposed below. Female terminalia 

 with 4 or 5 pairs of short, slender, apically rounded 

 spines; accessory spines appear to be absent. 



Distribution : Nearctic : Ablautus californicus Wilcox 

 (1935) ; coquilletti Wilcox (1935) ; fiavipes Coquillett 

 (1904) ; mcgregori Bromley (1934) ; mimus Osten Sac- 

 ken (1877); nigronotwm Wilcox (1935); rubens Co- 

 quillett (1904); rufotibMis Back (1909); squamipes 

 Cole (1924) ; trifarius Loew (1866) ; vanduzeei Wil- 

 cox (1935). 



