DASrrOGONINAE 



ROBBER FLIES OF THE WORLD 



S3 



Head, lateral aspect : The head is of medium length, 

 increased by the prominent occiput. The face is very 

 short above and almost even with the eye margin, be- 

 coming moderately prominent and rounded on a little 

 more than the ventral half. The eye is convex anteriorly 

 and nearly plane posteriorly ; the occiput is prominent 

 both above and below but slopes gradually away from 

 the eye margin towards the center of the head. It is 

 densely covered with long, coarse pile, which dorsally 

 changes to weak, bristly, proclinate pile. The probos- 

 cis is unusually short, scarcely extending beyond the 

 face, cylindrical, with truncate apex and numerous, 

 long, fine hairs ventrally upon the basal half. Dorsal 

 carina absent. Palpus exceptionally long and slender, 

 of two segments, extending almost the length of the 

 face. The basal segment is short, the pile scanty. The 

 antenna is attached at the upper third of the head ; it 

 is as long or longer than the head and the third seg- 

 ment a little longer than the first 2 segments combined. 

 The third segment is slender, of nearly uniform width 

 or a little narrowed subbasally and a little dilated sub- 

 apically. It has a short, comparatively wide, apically 

 rounded microsegment which may be dorsally open 

 with enclosed spine. 



Head, anterior aspect: The head is exceptionally 

 and unusually wide and the face a little less than one- 

 third the head width. The gibbous, or protuberant, 

 portion of the face is densely beset with long, slender 

 bristles and there are 7 or 8 shorter, bristly hairs on 

 each side of the upper face. The front is quite short, 

 considerably wider than the face, and with a conspicu- 

 ous tuft of numerous, long, stiff hairs along each eye 

 margin. The ocellarium is prominent with vertical 

 sides and several, long, bristly hairs. Vertex moder- 

 ately excavated, the sides with many long, stiff hairs. 

 Anterior eye facets strongly enlarged. 



Thorax: The mesonotum is quite low, thickly cov- 

 ered with conspicuous, flat appressed, curled pile 

 among which there are considerable number of fine, 

 long, erect hairs; bristles extremely weak. There are 

 2 or 3 notopleural, 2 supraalar, 3 or 4 postalar, and no 

 scutellar bristles. The whole scutellum is covered with 

 scattered, exceptionally long, fine hairs which on the 

 margin become a little stiffened and a little longer. 

 The scutellum is convex. Propleuron with stiff bristly 

 pile only. The presternum is fused in the middle be- 

 low and narrowly above. The lateral propleuron and 

 dorsal mesopleuron bear dense tufts of stiff pile. 

 Pteropleuron bare. Metapleuron with dense, long, 

 bristly pile. Metanotal callosity without pile. Post- 

 metacoxal area short but membranous. 



Legs : The hind femur is gradually dilated from the 

 base to the apex and densely beset on the dorsal, lateral, 

 and ventral surfaces with long, stiff, bristly pile; 

 medial surface with abundant, appressed, short pile. 

 Hind tibia stout, like the femur, with numerous, bristly 

 hairs on all sides except the medial, and many of these 

 hairs developed into slender bristles, of which there are 

 at least 5 rows, each containing 6 to 8 elements. Hind 

 basitarsus short and stout, the next 3 segments bead- 



like, their dorsolateral bristles long, stout and finely 

 attenuate. Anterior and middle femora and their 

 respective tibia moderately stout and their pile and 

 bristle components similar to that of the hind legs, 

 their tarsi also similar. The tarsi end in well de- 

 veloped pulvilli, a basally swollen empodium and sharp 

 claws. 



Wings : The wings are broad, the marginal cell dis- 

 tinctly open, the first posterior cell only slightly nar- 

 rowed, the fourth posterior and anal cells closed with 

 a long stalk. Upper and lower end vein of the discal 

 cell of equal length, the base of the second submarginal 

 cell strongly arched. Ambient vein complete, alula 

 well developed. Wing almost wholly villous. 



Abdomen: The abdomen is wider than the thorax, 

 rather strongly flattened and shining, with compara- 

 tively sparse, line, appressed pile in the middle of the 

 tergites ; this pile becomes longer and denser along the 

 lateral margin giving it a somewhat shaggy appear- 

 ance. There are six tergites present in thefemale with 

 an exceptionally narrow, linear trace of the seventh 

 tergite and hidden beneath the seventh a trace of the 

 eighth tergite may be seen. Female terminalia is 

 small, short, inconspicuous, without spines, the proc- 

 tiger protrudes a short distance beyond the last tergite. 

 No males were seen. 



Distribution: Neotropical: Hexameritia micans 

 Philippi (1865); splendens Philippi (1865); tricolor 

 Schiner (1868). 



Genus Gerrolasius Hermann 



Figures 34, 414, 917, 926, 1678 



Gerrolasius Hermann, Zool. Jahrb., vol. 43, p. 189, 1920. Type 

 of genus: Gerrolasius meridionalis Hermann, 1920, by 

 original designation. 



Small, compact, robust flies characterized by the 

 very short, curled, appressed, setate pile, the open pos- 

 terior cell, sigmoid anterior branch of the third vein, 

 the ambient vein complete to the anal cell, and the com- 

 paratively elongate, slender antenna. The hind femur 

 is distinctly but moderately swollen. Only the first 2 

 tergites bear lateral bristles, those of the second tergite 

 barely distinguishable from pile. Length 8 or 9 mm. 



Head, lateral aspect: Length of the head is two- 

 thirds the height. The eye is comparatively long and 

 very strongly convex anteriorly, plane through the 

 middle third posteriorly but strongly convex dorsally 

 and also recessive anteriorly on the lower third. The 

 occiput is quite short ventrally and obliterated on the 

 upper three-fifths. The pile of the occiput consists of 

 some short, scanty, stiff hairs extending along the mid- 

 dle and becoming a little longer ventrally ; this pile is 

 subappressed, more or less curled and directed outward, 

 and arises close to the eye margin. Set more deeply 

 within the occiput are 7 slender bristles on the ventral 

 half, 2 in the middle, a little more stout, and on the up- 

 per occiput, though deeply removed from the eye mar- 

 gin, are 5 or 6 quite stout pairs of nearly straight 



