ROBBER FLIES OF THE WORLD 



479 



mann (1828) ; quadrimaculatm Bellardi (1861) ; rapax 

 Osten Sacken (1887) ; rubldivenfr!,s Macqiiart (1849) ; 

 ruflmis "Wiedemann (1819) ; ru/lpes Macquart (1838) ; 

 rufithorax Macquart (1846) ; nifitibia Macquart 

 (1848) [ = fortis Walker (1855)] sagax Williston 

 (1901); schadei Bromley (1951); senilis Wiedemann 

 (1828); dcyon Walker (1849); singularis Macquart 

 (1838) ; splendem Williston (1901) ; stigmosus Carrera 

 and d'Andretta (1950) ; stimicon Walker (1851) ; stri- 

 ola Fabricius (1805) ; styUtm Fabricins (1775) i = cavr- 

 dex Walker (1849), haitensis Macquart (1848), in- 

 varivs Walker (1851)]; suhappendicuJatus Macquart 

 (1838) ; subchalyheus Bromley (1928) ; titan Bromley 

 (1934); tortola Curran (1928); triton Osten Sacken 

 (1887) ; unicolor Bellardi (1861) ; vauriei Curran 

 (1953) ; velox Wiedemann (1828) ; zetterstedtii Jaen- 

 nicke (1867). 



Country unlmown : Nerax asper Walker (1851) ; con- 

 color Walker (1851) ; inappendiculatus Macquart 

 (1838); leon Walker (1849); malis Walker (1849); 

 marcinus Walker (1849) ; nervosus Macquart (1838) ; 

 nitidus Wiedemann (1828); rohustus Walker (1855). 



This genus is one of the largest and most character- 

 istic elements in the New World to ■which it is confined. 



The species of this genus fall into two distinct groups 

 according to their habitat. There are those which, like 

 Nerax intert'uptus, are almost always found on the 

 ground surface and often on sand banks, mud flats or 

 hard baked fields. Tlie other group dwells on twigs 

 and trees. Nerax is a dominant genus in the semi- 

 arid lands of western America but is also plentiful in 

 eastern parts with higher rainfall and in much of South 

 America. Nerax interruptus shows certain anatomical 

 features which ally it to the Chilean LochtnorhyncJius 

 Engel. 



Malloch (1917) gives figures for immature stages of 

 two species of this genus, Nerax aestuans and inter- 

 ruptus, and Riley (1870) figures larva of Nerax fe- 

 inoratus Macquart. 



Genus Diplosynapsis Enderlein 



FiGTJBES 315, 698, 1436, 1445, 2436, 2480 



Diplosynapsis Enderlein, Zool. Anzeiger, vol. 44, p. 259, 1914. 

 Type of genus : Diplosynapsis argentifascia Enderlein, 1914, 

 by original designation. 



Large flies, immediately recognized by the closure of 

 both the marginal and submarginal cells ; the latter has 

 a short stalk. A few American species of Nerax, new 

 genus may have the submarginal cell virtually closed 

 or closed at the margin. The face is exceptionally 

 gibbous and abrupt above; the metanotal callosity is 

 creased behind and micropubescent only. Females 

 with greatly compressed ovipositor. Length 25 mm. 



Head, lateral aspect : The head is rather long, its 

 length augmented by the greatly produced facial gib- 

 bosity ; the eye posteroventrally recessive below. The 

 occiput behind the upper eye facet has 5 stout bristles. 

 The proboscis is without the strong, basal carina present 



in Nerax, new genus. Palpus large, with numerous 

 bristles. Antenna as in Nerax. 



Head, anterior aspect: The face is pubescent, ex- 

 tending on to the prominent cheeks and with a few, 

 scattered, lateral hairs on the gibbosity, including the 

 upper ledge; it bears numerous, exceptionally stout, 

 long bristles, continued down the sides of the deeply 

 concave pubescent, subepistomal area. Front small, ele- 

 vated, the vertex narrow and deeply excavated, 

 especially behind. The ocellarium is low, with 2 pairs 

 of long, slender bristles. Sides of front with ocular and 

 subocular rows of bristles. 



Thorax: The thorax is similar to that of Nerax, 

 with more scanty setae. The scutellum is convex, thick, 

 pollinose, with 3 pairs of scutellar bristles; the surface 

 beai-s erect, bristly hairs and the scutellum is thick, 

 convex, without impressed rim. Pronotum with only 

 dense, fine hairs, except at fartlierest lateral corners 

 where there are 2 stout bristles. Metanotal callosity 

 bullose and micropubescent only. Postmetacoxal area 

 with a complete chitinized arch behind the postcoxa 

 and with medial seam. Between this anterior band of 

 chitin and the posterior portion of the metasternmn is 

 a broad, transverse band of membrane. Prosternum 

 fully dissociated. Anterior basalare and posterior sec- 

 tion of pteropleuron each with several bristles; the 

 latter has longer but more slender elements. 



Legs : The legs are similar to Nerax. The anterior 

 four are only slightly swollen. Bristles are stout, long 

 and prominent. Claws are strongly bent at the apex 

 and comparatively blunt. Pulvilli and empodium well 

 developed. The hind femur has 2 lateral bristles, a 

 dorsal pair at the subapex and a medial bristle at the 

 apex, also with 6 ventrolateral bristles of which the 

 basal two are paired; in addition there are 6 ventro- 

 medial bristles, the basal element is paired, and also 2 

 medial basal bristles. Trochanters with 4 bristles, The 

 hind coxa has a strong, anterior, mammiform lobe bear- 

 ing 4 bristles below. 



Wings: The wings are tinged with pale brown ; there 

 are two submarginal cells only. The anterior branch of 

 the third vein arises as a rectangular crossvein with a 

 basal spur; the anterior branch ends at the wing apex, 

 the posterior branch ends far to the rear. The first 

 posterior cell is naiTow in the middle. Fourth posterior 

 cell closed and petiolate. Fork of the third vein oppo- 

 site or barely beyond the base of the second posterior 

 cell. 



Abdomen: The abdomen is attenuate, with scanty, 

 suberect setae, w'hich are slightly longer laterally. The 

 sides of the fii-st and second and basal comers of the 

 third tergite each bear fine, erect pile. Sternites with 

 quite long, fine, scanty pile. Sides of first tergite with 

 tliree stout bristles. Females with seven tergites, those 

 beyond incorporated into a quite long, high, greatly 

 compressed ovipositor; the ninth segment and the proc- 

 tiger is short. No males seen. 



Distribution: Neotropical: Diplosynapsis argenti- 

 fascia Enderlein (1914) ; halterata Enderlein (1914). 



