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UNITED STATES NATIONAL MUSEUM BULLETIN 224 



ends well above the wing apex and the base of the sec- 

 ond submarginal cell characteristically has a well de- 

 veloped spur vein. All posterior cells open, including 

 the second. Ambient vein complete as far as the anal 

 cell, or may be wholly absent. 



Abdomen: The abdomen is broad, robust and flat- 

 tened, wider than the thorax, very gently and only 

 slightly convex across the middle. The first tergite is 

 two-thirds as long as the second. Sides of all the ter- 

 gites with brownish yellow pile in appressed tufts; 

 that which is on the first tergite is slightly more stiff 

 and more erect. Middles of tergites with microscopi- 

 cally short, appressed pile; the surfaces are granulate 

 and shining. Postmargins of the tergites narrowly 

 bordered with flat, appressed, opaque, brownish white 

 pile. Some species have distinct patches of 5 or 6 ter- 

 gal bristles laterally on the first 6 tergites ; other species 

 have only shelflike fringes of dense, long pile. In the 

 males there are seven tergites, the seventh is one-third 

 as long as the sixth. In the female seven tergites are 

 visible, the last very short indeed but visible from above 

 and about one-fifth as long as the sixth which in turn 

 is only two-thirds as long as the fifth. Male terminalia 

 short and apparently not rotate, with a pair of slender, 

 sharp, downturned hooks from the gonopod. Female 

 terminalia very short, bearing 4 pairs of short, spatu- 

 late, apically rounded spines; accessory bristles absent. 

 Distribution : Palaearctic : Acnephalum ollvieri Mac- 

 quart (1838). 



Ethiopian: Acnephalum andrenoides Wiedemann 



(1828) ; cockeretti Curran (1934) ; decula Walker 



(1849) ; dorsale Macquart (1838) ; futile Wulp (1899) ; 

 platygaster Loew (1858); quadratum Wiedemann 



(1828). 

 Australian: Acnephalum punctipenne Macquart 



(1855). 

 Country unknown : Acnephalum coon Walker (1849) . 



C«nus Heteropogon Loew 



Figubes 109, 120, 522, 1035, 1041, 1992 



Heteropogon Loew, Linnaea Entomologica, vol. 2, p. 488, 1S47. 

 Type of genus : Dasypogon manieatus Meigen, 1820. Desig- 

 nated by Back, 1909, the first of 3 species. 



Heteropogon has 1 subgenus, Anisopogon Loew. 



Medium size to rather small flies, rarely large. They 

 are characterized by reduced pile, which is quite short 

 on the thorax and abdomen and the long, exceptionally 

 slender, third antennal segment, which carries with it 

 a style as long as the third segment. In the male there 

 is a further character of some interest in the large, 

 downwardly curved, smooth, convex epandrium, which 

 is at most only notched apically. In this condition they 

 are similar to Pycnopogon Loew and from that genus 

 they seem most readily differentiated by the scanty pile 

 and the usually longer, more slender antennal style. In 

 Pycnopogon the vertex and lower face are both dis- 

 tinctly wider than the face at the antenna. Also, many 

 of the species of Heteropogon tend to have a rather 



high mesonotum with the head held somewhat down- 

 ward, the abdomen often drooping and thereby accentu- 

 ating a hump-backed appearance. Length 7 to 23 mm. 



Head, lateral aspect: The face is short, scarcely 

 visible in profile and slightly convex; occasionally it 

 is a little more produced ventrally; the face profile 

 is often plane. Eye of moderate length, strongly con- 

 vex both anteriorly and posteriorly; usually without 

 posteroventral recession ventrally but moderately re- 

 cessed in a few Palaearctic species. The occiput is 

 well developed, tapering gradually near the vertex to 

 the eye margin; throughout the middle and below it 

 is quite prominent. The eye is sometimes short, very 

 strongly flattened in front and equally developed above 

 and below. The proboscis is plane below, gently 

 tapered at the apex dorsally, with a prominent, medial 

 ridge ; the apex is obtusely rounded, chiefly from above, 

 and bears a number of fine hairs. The proboscis is 

 distinctly compressed laterally and only very slightly 

 swollen towards the base; there is a ventral, medial 

 fissure in the middle ; base below with numerous, long, 

 fine hairs. Proboscis usually directed downward and 

 slightly forward. Palpus with the first segment short, 

 excavated, and distinct. Second segment elongate, 

 cylindrical, or a little swollen in the middle, tending 

 to be attenuate apically with an apical pore and a mod- 

 erate number of slender, bristly hairs on the middle 

 dorsally and laterally but for the most part not apical. 

 However, there are one or more apical bristles in several 

 species, and it may be covered with bushy pile, the 

 whole segment swollen. 



The antenna is attached at the upper third of the 

 head and unusually slender; first two segments rather 

 short, of equal length. The third segment is elongate, 

 attenuate apically ; at its widest it is scarcely as wide 

 as the second segment; it carries apically two micro- 

 segments which are held at a slight angle or in some 

 instances no angle at all. The first microsegment is 

 quite short; the second microsegment is fine and attenu- 

 ate and often as long as the third segment itself; in 

 other cases as little as two-thirds the length of the 

 third segment; it has a minute, apical spine. Pile of 

 the first two segments usually consists of several long, 

 slender bristles ventrally with shorter bristles dorsally ; 

 pile of second segment similar but from the middle 

 below there is characteristically a single veiy long, 

 stiff bristle, usually as long or longer than the two 

 first segments combined. 



Head, anterior aspect: The face below antenna is 

 about two-fifths of head width, the sides parallel and 

 therefore not divergent below. Subepistomal area 

 rather small and nearly horizontal, concave and bare. 

 Face pubescent, with a mystax above the epistoma rang- 

 ing from 3 or 4 pairs of weak, fine bristles to 5 or 6 

 pairs of quite stout, long bristles or with still more 

 bristles arranged in several rows. Rarely the bristles 

 may be obscured by dense, fine pile which extends in 

 somewhat diminished density up to the antenna. Front 

 of moderate length, nearly plane with the eye, dis- 

 tinctly divergent; the divergence of the front is con- 



