ROBBER FLIES OF THE WORLD 



475 



laterally. Pile scanty, flat appressed setae with 4 or 5 

 stout, long bristles present on the sides of the first ter- 

 gite. Posterolateral corners of fifth to seventh tergites 

 with 2 or 3 strong, bristly hairs, no distinct bristles. 

 Stemites with appressed setae and no bristles. Eight 

 tergites present in males, the eighth concealed dorsally 

 and quite short laterally. Seven tergites present in the 

 female, the eighth incorporated in ovipositor. Male 

 terminalia rather large and robust but short, the su- 

 perior forceps are convex laterally, extend in at apex to 

 meet medially with only a very small dorsal notch. 

 Proctiger exceptionally large and directed obliquely up- 

 ward. Gonopod prominent laterally and together with 

 claspei-s set at an angle downward and then sharply bent 

 upward so that a space shows between. Hypandrium 

 well developed. Female terminalia are short, especially 

 the terminal segments. In the female the eighth is as 

 long as high and slightly compressed laterally and in 

 consequence not quite cylindrical. The ninth and tenth 

 segments are exceptionally short and rather strongly 

 compressed laterally; tenth sternal element narrow, 

 high, very short and cleft, the two halves tightly ap- 

 posed. 



Distribution : Neotropical : Eicherax eupator Walker 

 (1851) ; favescen-s James (1953) ; macvlaris Wiede- 

 mann (1821) ; nigripes Bellardi (1861) ; nigrimystaceiis 

 Macquart (1847) ; simplex Macquart (1848) ; ncnotes 

 Engel (1930) ; villosus Bellardi (1861). 



Genus Efferia CoquiUett 



FiGUEE 800 



Efferia CoquiUett, Canadian Ent., vol. 25, p. 175, 1893. Type 

 of genus: Efferia candiclus CoquiUett, 1893. Designated 

 by CoquiUett, 1910, the fifth of 5 species. 



Large flies, similar to Nerax, new genus and readily 

 distinguished by the presence of 3 submarginal cells. 

 The spur beyond the crossvein at the base of the anterior 

 branch of the third vein is extended completely back to 

 the second vein without intergrades ; this spur consti- 

 tutes the base of the posterior branch of the second vein, 

 which has become fused with the anterior branch of 

 the third vein. Marginal cell is extremely narrow both 

 at base and at apex and the posterior branch of the third 

 vein ends well above the wing apex. The costa is never 

 dilate. These are pale grey or yellowish white colored 

 flies ; the thorax bears brownish yellow pollen and the 

 abdomen has much silvery grey pollen, so that they 

 tend to match the color of the sandy, arid regions of 

 which they are inhabitants. Length 15 to 30 mm. 



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

 with the gibbosity only moderately developed but more 

 conspicuous because of the gradual, strong, posterior 

 recession of the eye which leaves the eye short and thin 

 below. The cheeks are quite prominent and high. The 

 proboscis is quite stout with a blunt apex. Subepistomal 

 area deeply concave, without medial ridge and in con- 



trast to Nercux its whole surface is coarsely pubescent. 

 The upper occiput bears 7 erect, stout bristles. The 

 face is pubescent, with nimierous, coarse, bristly hairs 

 and with stout bristles confuied to the epistomal mar- 

 gin wliere there is a transverse row of 6 pairs. Antenna 

 as in Nerax, the front and vertex likewise. The small, 

 low ocellarium has 1 pair of stout, long bristles and sev- 

 eral, additional, fine, shorter hairs. 



Thorax : The thorax is similar to Nerax ; the metano- 

 tal callosity also bare and the anterior basalare with 

 slender bristles. Postmetacoxal area membranous and 

 pilose. Prosternmn dissociated. 



Legs : The legs are similar to Nerax but with the 

 femora generally more swollen; all the femora and 

 tibiae bear long, rather dense, delicate fringes of 

 ei-ect pile on their ventral surfaces, more copious 

 on the tibiae. Bristles, where present, are exceptionally 

 stout, long and blunt. Hind femur with 3 lateral, 4 

 ventral on the basal half, and 2 ventrolateral distal 

 bristles; there is a pair of bristles dorsally at the sub- 

 apex but at the apex there is only a medial bristle. 

 Middle femur with 2 anterior bristles, 1 distal antero- 

 ventral, and 6 conspicuous, posterior bristles. Bristles 

 are absent on the anterior femur. Hind tibia with 2 

 anterodorsal, 3 posterdorsal, 1 anterior at the outer 

 third, and 1 anteroventral beyond. The apex bears 5 

 bristles. Middle tibia with 3 posterodorsal, distal 

 bristles and 1 long ventral bristle on the outer fourth; 

 the anterior tibia has 4 dorsal, 2 basal anterior dorsal, 

 and a single, long, distal posterior bristle. Basitarsus 

 throughout short and slightly longer than the next 2 

 segments. Anterior and posterior bristles of the first 4 

 tarsal segments exaggerated. Claws long, stout, a little 

 blunt; the pulvilli and empodium well developed. 



Wings : The wings are much like Nerax except for 

 the presence of 3 complete submarginal cells. The wing 

 is exceptionally slender, the first branch of the medius 

 ends far behind the wing apex. 



Abdomen: The abdomen is elongate, basally stout 

 and strongly tapered, especially in females. The sur- 

 face is pale pollinose, the pile abmidant, subappressed 

 and setate with long, laterally directed tufts on the 

 second and third tergites and radiating tufts on the 

 strongly protuberant margins of the first tergite. Sides 

 of the first tergite with 3 or 4 quite stout bristles, usual- 

 ly pale. The lateral tufts of pile in the male are medial- 

 ly divided and of a fine and crinkled texture. Males 

 with eight tergites. The superior forceps unusually 

 long and strongly compressed, particularly on the basal 

 portion. Female with the eighth segment long and flat- 

 tened, laterally compressed and striate; the ninth seg- 

 ment is shorter and together with the proctiger like- 

 wise greatly compressed. 



Distribution: Nearctic: Ejferia anomalus Bellardi 

 (1861) ; candidus CoquiUett (1893) ; pemicis CoquiUett 

 (1893). 



Neotropical: Efferia lati forceps Bromley (1928); 

 neowillistoni Bromley (1933). 



