32 



UNITED STATES NATIONAL MUSEUM BULLETIN 2 24 



bare and with medial carina. Front short, due to the 

 position of the antenna attached at the upper seventh 

 of the head. Front nonpubescent with long bristly 

 hairs laterally, the vertex is scarcely excavated, the 

 ocellar protuberance quite low with vertical sides and 

 all the ocelli enlarged. Between the ocelli there are 

 long stiff hairs. 



Thorax: Mesonotum comparatively low and uni- 

 formly convex anteriorly and posteriorly, shining, 

 without pubescence but with dense, coarse, rather long, 

 subappressed pile. Bristles absent. Scutellum con- 

 vex with long coarse erect, discal and marginal pile. 

 Propleuron and collar densely long pilose, without 

 bristles. Mesopleuron with long pile dorsally and 

 similar but less abundant pile present on the posterior 

 hypopleuron, anterior and posterior sternopleuron. 

 The swollen metapleuron with abundant pile and a 

 number of long bristly hairs. Much of the pleuron 

 is polished and bare, its pubescence chiefly restricted 

 to the metapleuron and posterior hypopleuron with 

 small patches elsewhere. Metanotal callosity with a 

 patch of coarse pile in addition to pubescence. Squa- 

 mae with a long fringe, slopes of the metasternum 

 pilose, postmetacoxal area membranous. 



Legs: All the femora moderately stout, especially 

 the middle and hind pairs and densely covered with 

 long, fine pile on all surfaces. Bristles absent. On the 

 tibiae there are on all surfaces rows of quite long, very 

 slender, bristly hairs. On the tarsi there are some dis- 

 tinct though slender bristles which become stouter on 

 the lateral and medial margins. Claws sharp, curved 

 from the base; pulvillus well developed. Empodium 

 reduced and strongly swollen at the base. The tarsal 

 segments are unusually short, the three intermediate 

 segments monilliform, the basal segments not quite as 

 long as the two succeeding segments. 



Wings : Marginal, all the posterior cells and the anal 

 cell widely open. Fourth posterior cell slightly nar- 

 rowed, the middle end vein of the second basal cell pres- 

 ent. Alula short. Ambient vein complete. 



Abdomen: Broad, nearly or quite as wide as the 

 thorax in the females. Slightly less wide in the males. 

 Seven tergites present in the male with a linear trace 

 of the eighth. In the female eight tergites present, 

 with the seventh half as long as the sixth. Abdominal 

 pile abundant, coarse, erect and brushlike laterally, 

 appressed dorsally. Male terminalia not or only 

 slightly rotate to the left. The epandrium wide, thin, 

 uncleft and at most very shallowly excavated, and bear- 

 ing long, flat, apically rounded, sharp-edged, lateral 

 protuberances. Gonopod largely concealed but with 

 two prominent, acutely pointed, narrow protuberances. 

 Hypandrium short, narrow, broad at base. Female 

 terminalia short, without terminal spines, the basal 

 plate laterally with a stout, blunt, downward turned 

 protuberance. There is considerable similarity of both 

 the male and female terminalia to those of Myelaphus 

 Bigot. 



Distribution: Nearctic. Dicolonus simplex Loew 

 (1866) ; sparsipilosum Back (1909). 



Palaearctic. Dicolonus argentatus Matsumura 

 (1916). 



Genus Myelaphus Bigot 



Fioubes 29a, 29b, 398, 844, 853, 1677, 1887, 1948 



Myelaphus Bigot, Bull. Soc. Ent. France, ser. 6, vol. 2, p. xci, 

 1882. Type of genus: Myelaphus melas Bigot, 1SS2, by 

 monotypy. 



Myielaphus Kert^sz, Catalogus dipteroruin . . ., vol. 4, p. 96, 

 1909. Emendation. 



Peculiar flies, characterized by the subglobular head, 

 the dorsal protuberance of the face and front on which 

 the extremely long antenna is set. The third antennal 

 segment bears 2 peculiar microsegments, the first short 

 but with 2 divergent, apical, lappetlike extensions, 

 the third longer and attached between these lappets. 

 Mesonotum rather humpbacked and convex, densely ap- 

 pressed pilose and without lateral bristles except for 2 

 weak, rather short, notopleural bristles. The head is 

 set rather low on the thorax and the abdomen is droop- 

 ing and these features tend to emphasize the hump- 

 backed appearance. Length including antenna 12 to 

 14 mm. 



Head, lateral aspect: The face is rather prominent, 

 especially on the upper half; this extension involves 

 the front also and constitutes a rounded, domelike pro- 

 tuberance bearing the antennae; these structures are 

 directed strongly upward. The face just below the 

 middle has a rounded, protuberant, transverse exten- 

 sion leaving the intervening area concave and the low- 

 ermost face strongly receding. The eye is unusually 

 long, a little more narrow above and quite convex ante- 

 riorly ; it is nearly plane on the upper half of the poste- 

 rior profile, the lower half strongly convex due to a 

 gradual anteroventral recession. The occiput is excep- 

 tionally thick in the middle and ventrally, and particu- 

 larly toward the medial portion ; it slopes rather grad- 

 ually down to the eyes and is receding and obliterated 

 dorsally. Pile of occiput moderately abundant, coarse 

 and almost bristly in the middle though rather fine, 

 scanty and not very long ventrally. Dorsally are a 

 few, slender, proclinate, bristly hairs. The proboscis is 

 swollen towards the base both in lateral and dorsal as- 

 pect ; it is subcylindrical distally with a bluntly rounded 

 apex; it carries a number of short, stiff hairs placed 

 apically and in a ventrolateral row which extends over 

 the entire outer third of its length. The subbasal 

 ventral portion bears numerous fine, long hairs; dorso- 

 medial ridge absent. The proboscis is directed hori- 

 zontally forward and extends a short distance beyond 

 the face. Palpus of 2 segments, the first segment exca- 

 vated, the second not porate and set at a slight angle, 

 short, more slender with apical bristles and with some 

 stiff, dorsal lateral and medial hairs. 



The antenna is attached on the swollen and rather 

 protuberant upper face and front almost on a plane 

 with the vertex; it is attached about one-fifth way 

 down below the upper eye margin. The antenna is 

 extraordinarily long and peculiar. The first segment 



