ROBBER FLIES OF THE WORLD 



487 



Genus Proctacanthus Macquart 



FiGUEES 391, 721, 1421, 1430, 2291, 2325, 2472, 2478 



Proctacanthus Macquart, Dipt§res exotiques, vol. 1, pt. 2, p. 120, 

 1838. Type of genu.?: Proctacanthus philadelphicus Mac- 

 quart, 1838. Designated by Coquillett, 1910, the seventh 

 of 9 species. 



Acanthodelphia Bigot, Ann. Soc. Ent. France, ser. 3, voL 5, p. 

 545, 1857. No species named. 



Large, conspicuous flies, cliaracterized by the elon- 

 gate, tapered abdomen, wliicli extends beyond the wings 

 and the position of tlie brandies of the third vein, both 

 of which end distinctly above the wing apex. Females 

 bear a conspicuous band or hemicircle of very stout 

 spines at tlie apex of the ovipositor in addition to other 

 dense, small setae ; this is one of the characters which 

 separates them from the Palaearctic flies of the genus 

 Satanas Jacobson, which resemble P roctacanthus. 

 The extension of the abdomen beyond the wings and 

 the more slender forms separate them from Eccritosia 

 Schiner. Length 20 to 45 mm. 



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

 with the eye narrowed below and strongly recessive pos- 

 tero vent rally on the lowest fifth. The face is short 

 beneath the antenna, but on the lower two-thirds and 

 sometimes three-fourths is a very prominent and con- 

 spicuous gibbosity; the cheeks below the eyes are ex- 

 tensive and well developed. The occiput is prominent 

 especially through the middle and below but reaches its 

 greatest thickness submarginally and beginning at or 

 below the middle of the head it bears bristles which 

 sometime extend to the lower third. The upper bristles 

 are stout and there is generally considerable pile on 

 the upper half and vei-y dense, long, fine pile on the 

 lower half of the occiput. Proboscis robust, blimtly 

 pointed, with conspicuous, long, bristly pile on all sides 

 of the apex and dorsally on the apical fourth. Gen- 

 erally thei'e is a prominent, dorsal carina on the basal 

 half and in some species the long, coar.se pile ventrally 

 and laterally is exceptionally abimdant and extends 

 from the base to or beyond the middle. The pale colored 

 species liave a proboscis which approaches that of Ec- 

 critosm in having the large, boatlike swelling ventrally. 

 Palpus prominent, long and robust, with numerous, 

 long, coarse hairs and bristles. The antemia is attached 

 below the upper third of the head and of moderate 

 length. The third segment is long oval and slightly 

 attenuate on the distal half; microsegments are absent 

 and the tliick style is generally shorter or at least no 

 longer than the combined length of all segments. 



Head, anterior aspect: The face below the antenna 

 from a fourth to a fifth the head width and strongly 

 divergent below. Face pubescent, the whole of the gib- 

 bosity beset either with dense, slender, long bristles 

 and coarse pile, or with very stout bristles mixed with 

 slender bristles and bristly hairs. The stout bristles are 

 characteristically continued down the sides of the epis- 

 tomal area; pile is absent on the not gibbous upper 

 portion of the face. Front large, pollinose, simken in 



the middle ; the antenna is set rather far apart ; the sides 

 of the front liave a long, oval patch or band of bristles 

 which may be often of varying length and thickness. 

 On the front the sides are slightly divergent, converg- 

 ing again at the vertex ; the vertex is deeply excavated 

 with steeply sloping sides, the ocellariiun large but low 

 and bearing 3 or -i pairs of vei-y stout bristles between 

 the ocelli and 2 to 4 pairs behind the ocelli. The ocelli 

 are frequently reduced, especially the anterior elements. 

 Medial eye facets enlarged. 



Thorax : TIae mesonotum moderately high, long and 

 pollinose. The pile consists chiefly of short, stubby 

 setae, widely scattered. Acrostical elements are not dif- 

 ferentiated and dorsocentral bristles only at the anterior 

 plane of the postalar, wliere there may be on each side a 

 single row or more often several rows containing 3 to 

 6 long, stout bristles. Humerus with short bristles or 

 very stout setae. The lateral complement of long, stout 

 bristles includes 2 notopleural, 1 supraalar, 1 or 2 supra- 

 postalar, and 2 to 4 postalar ; the scutellar margin con- 

 tains 2 to 6 pairs of stout bristles and there are gen- 

 erally at least 3 otlier transverse rows of stout bristles 

 on the disc, besides other bristly pile. Scutellum very 

 thick and convex, without impressed rim. Pronotum 

 with 8 to 10 paii-s of stout bristles. Upper border of 

 the mesopleuron with short, flat appressed setae or 

 long, bristly liairs. Upper sternopleuron, posterior 

 mesopleuron, and the pteropleuron and posthypopleur- 

 on with scattered pile. Metapleuron with 10 or more 

 quite stout bristles. Metanotal callosity pollinose only. 

 Prosternum dissociated, iletasternmn pilose; post- 

 metacoxal area membranous; anterior basalare with 

 both bristles and setae. 



Legs : The middle and posterior coxae with stout, lat- 

 eral bristles; hind coxa and trochanters with 2 or 3 

 equally stout, postmedial bristles. The femora are quite 

 stout, comparatively elongate and the first 4 distinctly 

 swollen on the basal half and middle. Bristles are con- 

 spicuous, numerous, very stout, and rather sharp. Pile 

 is short, subappressed, and setate and there are no con- 

 spicuous fringes of pile ventrally on either femora or 

 tibiae. Hind femur with 3 or 4 lateral bristles, 8 to 10 

 ventrolateral and a like number of ventromedial bris- 

 tles. Also tliere are a transverse, dorsal, subapical pair 

 and 2 dorsoinedial bristles at apex. The hind tibia bears 

 5 dorsolateral, 4 dorsomedial and typically 3 or 4 ven- 

 trolateral elements, besides 3 ventrolateral bristles. 

 Middle femur with 4 anterior and 5 to 10 posterior 

 bristles, 4 or 5 anteroventral and 8 to 12 posteroventral 

 bristles. Middle tibia often with only a single, long, 

 stout, anterodorsal bristle near or beyond the middle 

 and sometimes a few additional short elements and 

 with 4 or 5 posterodorsal bristles sometimes reduced to 

 2 stout bristles. Anterior femur with a posterodorsal 

 band of 8 to 14 irregularly placed, short, weak bristles 

 and with ventrally 8 to 14 quite stout, long bristles. 

 Bristles are rather better developed on the anterior 

 tibia, stout but short, except posteroventrally where 

 they are longer. There are 8 anterodorsal, 10 postero- 

 dorsal, 4 posterior and 2 to 4 posteroventral bristles. 



