DASTPOGOSINAB 



ROBBER FLIES OF THE WORLD 



223 



anterior tibia may be polyphyletic, since it is evident 

 that there are at least two subdivisions, the one having 

 a small, slender, twisted or bent spine, without any 

 accompanying basal protuberance, and composed of 

 many genera of small flies; and another division of 

 medium or large flies with a stout, straight spine, with 

 or without a basal protuberance, and often with an 

 accompanying swelling and denticles on the base of the 

 corresponding basitarsus. While it seems likely that 

 these tibial spines have arisen more than once, it is 

 scarcely tenable to hold that they have arisen on any 

 multitudinous basis. I regard them as a specialization 



and as an adaptive structure useful to the insect for 

 raptorial purposes. It should be noted that the aux- 

 iliary denticles and plate augment the value of the 

 spine; the denticles arise earlier than the plate of the 

 basitarsus, and the plate itself has arisen independently 

 as in the Megapodinae. 



The tribe Stenopogonini contains some genera which 

 bear a striking resemblance to certain other genera 

 among those of the spined front tibia of the Dasypo- 

 gonini. I refer to ArchUestris Loew and Dlogmites 

 Loew ; to Cyrtopogon Loew and Lestomyia Coquillett ; 

 and to Eueyrtopogon Curran and Comantella Curran. 



KEY TO GENERA OF DASYPOGONINI 



1. Anterior tibia always with spine, or with protuberance and 



spine at the apex ; the spine is either fine or stout, sharp or 

 blunt, straight or twisted and bent. Marginal cell always 

 open. Female terminalia always with acanthophorites 

 and spines. Male terminalia always rotate. Lateral 

 slopes of metasternum with pile. Presternum dissoci- 

 ated 2 



Anterior tibia never with protuberance or spine at apex; 

 marginal cell always open. Female terminalia always 

 with acanthophorites and spines. Male terminalia with 

 or without rotation. Lateral slopes of the metasternum 

 always with pile. Prosternum characteristically dissoci- 

 ated Stenopogonini 



2. Anterior tibia at apex with protuberance bearing doubled 



spine, the outer element longer and twisted. Large, 

 densely, short pilose flies. 



Questopogon Dakin and Fordham 

 Anterior tibia always with a single spine at apex, straight 

 or bent, slender or stout, and with or without protuber- 

 ance 3 



3. Third antennal segment with small, dorsal or sublateral 



spine, usually more or less concealed by a dorsal depression 

 near the apex ; spine sometimes free and with accompany- 

 ing excision. Pulvilli always present and well devel- 

 oped 4 



No dorsal or sublateral, subapical spine present on third 

 antennal segment or if present, the pulviUi are wanting. 

 Ordinary bristles present or absent 6 



4. Subfacial sclerites (area beneath mystax) much shorter 



than the face. Antenna elongate and slender, without 

 dorsal bristles; antennal spine often free, with well 

 marked, dorsal incision and spine, basitarsal protuberance 

 and basitarsal modifications absent ; fourth posterior cell 

 open. Small flies ; abdomen never elongate or constricted. 



Taracticus Loew 

 Subfacial sclerites as long as the face. Third antennal 

 segment with several, stout bristles dorsally ; anterior 

 tibia with spine and basitarsus with prominent, swollen 

 flange. Fourth posterior cell closed and petiolate. Slender 

 flies, exceptionally bare, scantily setate, with the abdomen 

 lengthened and more or less narrowed basally ... 5 



5. Third antennal segment robust, rather short, with apical pit 



and spine and poorly differentiated, lateral spine beyond 

 the middle; its length from 1 to 1% times that of the 

 combined length of the first two segments. Second ab- 

 dominal segment with low, broad, distinct bullae anteriorly 



and posteriorly Mirolestes Curran 



Third segment long and slender, with middorsal incision and 

 spine, its length more than 2 times the combined length 

 of the first two segments Ctetopheys Loew 



6. Fourth posterior cell closed and stalked 7 



Fourth posterior cell open and usually widely open . . 22 



535914 — 62 — pt. 1 16 



7. Third antennal segment without microsegmeut ; apex with 



a minute spine, or spine absent 8 



Third antennal segment with a distinct and well developed 

 apical microsegment 20 



8. Scutellum with stout bristles 9 



Margin of scutellum without bristles 18 



9. Pulvilli of hind legs and sometimes the middle pair reduced 



to a third the claw length . . . Caenabolia Thomson 

 Pulvilli of normal length 10 



10. Width of face greater than a third the head width; face 



usually with some fine pile . . . Allopogon Schiner 

 Width of face less than a third the head width ... 11 



11. Third antennal segment elongate, cylindroid, with apical pit 



and approximately twice the combined length of first two 

 segments. Bare, black flies of greatly reduced pile and 

 few bristles. Form short and robust. Fourth posterior 

 cell closed with very short stalk or very narrowly open. 



Apothechtxa, new genus 



Third antennal segment shorter, spindle-shaped, or dilated 



throughout the middle ; apex with spine 12 



12. Face usually completely apilose and mystax confined to 



1 or 2 rows of stout, long bristles. Elongate flies, usually 

 with narrow abdomen, cylindroid or slightly tapering, 

 rarely subclavate. Pile greatly reduced, presenting a bare 



appearance 13 



Face often densely pilose; mystax forming a cluster of 

 ventral bristles. Shorter, more robust species, densely 

 pilose 15 



13. Middle of front with abundant, bristly pile. Ocellarium 



with several pairs of bristles. Sides of abdomen basally 

 with abundant, fine pile. Large or very large flies. 



Neodiogmites Carrera 



Middle of front usually apilose. Abdomen without dense, 



basal and lateral pile 14 



14. Ocellarium with 5 pairs of bristles. Third antennal seg- 



ment without bristles. Front without bristles. 



Chtlophaga, new genus 

 Ocellarium usually with 1 pair of bristles. Third antennal 

 segment usually with several, stout bristles. Front gen- 

 erally without bristles Dioomites Loew 



15. Face entirely convex throughout and densely beset with 



stiff pile or weak bristles .... Lastatjrtna Curran 



Face with at least the upper fourth bare ; all of face usually 



bare, except the supraepistomal gibbosity; face gently 



concave 1" 



16. Pile or bristles of face restricted to a supraepistomal 



band 17 



More elongate flies, the pile fine, silky and dense and extends 

 over the lower three-fourths of the face ; no bristles above 

 epistoma Lastaubopsis Carrera 



17. Palpal segments continuous .... Lastatjbax Carrera 

 Palpal segments discontinuous (including Lastauroides Car- 

 rera) Lastaubus Loew 



