I.APBRIINAE 



ROBBER FLIES OF THE WORLD 



329 



the upper half, the ventral surface plane. The anterior 

 branch of the third vein straight, ending approximately 

 at the wing apex. Length 12 to 24 mm. 



Head, lateral aspect : Head of moderate length, the 

 eye rather short, high and flattened anteriorly. The 

 occiput is developed only on the lower half; the eye 

 is moderately recessive. Face with a low but distinct 

 gibbosity on the ventral half, a smaller one beneath the 

 antenna and concave between. The occipital pile is 

 fine and moderately abundant; the dorsal bristles al- 

 ways slender and deeply placed and restricted to the 

 upper third. The proboscis is unusually long, not very 

 high but strongly compressed laterally and the punc- 

 tured apex blunt. Palpus of two segments, the second 

 cylindrical, with bristles on all sides and the apex. The 

 antenna is attached at the upper fourth of the head, or 

 higher, moderately long, the first segment nearly twice 

 as long as the second, with at least 1 stout, long bristle 

 and both segments with short, bristly pile both above 

 and below. The third segment is a little wider than the 

 second, sometimes attenuate on the basal half, widest 

 beyond the middle and tapering rather rapidly to a 

 blunt point. 



Head, anterior aspect : The head is wide and a little 

 wider than the thorax or at least as wide. The face 

 is not quite one-fourth the head width, with parallel 

 sides. The face is covered with fine, appressed pubes- 

 cence and scalif orm pile laterally ; typically there are 

 3 to 5 pairs of very long, somewhat bent, wiry bristles 

 placed in 2 vertical rows, among which there is a little 

 fine, scattered pile and all of this pile or these bristles 

 situated on the gibbosity of the face. Sometimes, in- 

 stead, the whole gibbosity is densely beset with irregu- 

 lar, long, slender bristles ; and possibly these two types 

 are unrelated. Subepistomal area moderately large, 

 concave, and oblique. Front and vertex distinctly di- 

 vergent, the former very short, pollinose and like the 

 face generally golden or silvery in color; the front 

 has only a few, fine, slender, bristly hairs. The vertex 

 is deeply excavated with sloping sides, the ocellarium 

 low with a pair of very stout bristles. 



Thorax: The mesonotum moderately high and con- 

 vex, the greater part of it usually shining and often 

 with conspicuous spots of bright pollen which are 

 either on or behind the humerus. The abundant, fine, 

 subappressed, setate pile, or the dense curled flat ap- 

 pressed pile is poorly differentiated. There may be a 

 row of fine, scanty, never long or stout dorsocentral 

 elements extending over the entire length of the thorax. 

 Lateral bristles are generally stout and consist of 1 

 notopleural, 3 or 4 supraalar, 2 or 3 postalar and 1 to 

 3 scutellar pairs of bristles. The scutellum is convex, 

 bare, metallic, with a few, fine, bristly hairs. Metano- 

 tal callosity pollinose only. Mesopleuron with a stout 

 bristle and some bristly pile posteriorly and a little pile 

 along the dorsal border. Propleural pile fine and 

 rather scanty with a few slender bristles on the pro- 

 notum. The humerus has bristly pile. The pro- 

 sternum is fused and continuous in a wide band. 

 Metapleuron with a triangular patch of numerous, 



long, slender bristles and bristly pile. Pleuron rather 

 uniformly pollinose. Metasternum pilose; postmeta- 

 coxal area membranous but generally greatly narrowed 

 by medial extensions of the lateral sclerites. Upper 

 sternopleuron with a tuft of pile and pteropleuron with 

 some scattered hairs. 



Legs: The legs are rather bare, shining and metallic; 

 the pile is fine and appressed and setate dorsally and 

 strongly reduced, especially on the tibiae. Ventral 

 surfaces of all femora plane; bristles are few and 

 slender and best developed on the middle tibia. Hind 

 femur with a stout bristle laterally at the outer fifth, 

 another above and dorsomedially, besides some slender 

 bristly hairs dorsally and fine, erect, but scanty hair 

 ventromedially, besides some slender, bristly hairs 

 dorsally and fine, erect, but scanty hair ventromedially ; 

 the corresponding fringe of tibia is also scanty. Middle 

 femur with stouter bristles, 1 posteriorly at the outer 

 fifth, 1 anteroventrally at the outer fourth. Anterior 

 femur with only some long, dorsal, bristly hairs and 

 long, more slender hairs ventrally, similar to that 

 found on the middle femur. Posterior tibia with 3 or 

 4 dorsal bristles; the strongest element is at the outer 

 third and there is a single, distal, dorsolateral bristle 

 and ventrolateral bristle near the apex. Middle tibia 

 with 3 or 4 exceptionally strong, long, attenuate, an- 

 terodorsal bristles and a like number of equally long, 

 posteroventral bristles; also there are slightly shorter 

 posterodorsal bristles of 3 or 4 in a row, and a similar 

 number of more slender, posterior bristles. On the 

 anterior tibia there are 2 groups of rather close-set 

 bristles anterodorsally near the apex, with 2 in each 

 group, all of them long. The apical bristles are set 

 rather far back from the apex. The anterior tibia is 

 sometimes a little bent. Claws sharp, bent at the apex ; 

 pulvilli large ; empodium bladelike. 



Wings : The wings are hyaline or pale grey, or rarely 

 banded ; in some species the wings are rather dark blue- 

 black or brown. The wing is elongate, the marginal 

 cell stalk quite long. The anterior branch of the third 

 vein is nearly straight, ending at the wing tip, the pos- 

 terior branch ends far to the rear. First posterior cell 

 slightly narrowed, the fourth posterior cell closed with 

 a long stalk. The lower end vein of the discal cell is 

 long and pulled towards the base. Alula large ; ambient 

 vein complete. 



Abdomen : The abdomen is robust and often a little 

 widened distally ; it is shining and metallic with dense, 

 fine, appressed pile and a few, scattered, fine, long hairs 

 laterally. Generally at least four tergites have distinct, 

 lateral bristles, usually stout, but sometimes slender. 

 Males with seven tergites, the last well developed and 

 prominent. Females with seven tergites, the seventh 

 about a third to a half as long as the sixth. Eighth 

 tergite short or long, conical and cylindrical and form- 

 ing the base of the ovipositor. Male terminalia rotate 

 one-half. The epandrium is long, shallow and bowllike, 

 the gonopod prominent but narrow, the hypandrium 

 is very short and concealed. Genital cavity widely open. 



