ART. 9 PLIES OF THE GENUS STYLOGASTER ALDEICH 3 



]ar 1. All these bristles are large, contrasting strongly with the 

 insignificant hairs occurring elsewhere on head and thorax. 



Specific characters. — The relative length of the second and third 

 antennal joints ; size of frontal triangle ; color of front ; extent of 

 pale color bordering humerus behind and mesially; extent of pleural 

 dark stripe; color of lateral bristles of first and second abdominal 

 segments and of the area on which they arise; curvature of last 

 section of fourtii vein; direction of hind crossvein; length of 

 second vein ; number of humeral, notopleural, and supraalar bristles. 

 The males show some good genitalic differences, and the female 

 ovipositor has several striking differences in color and length of its 

 joints. In all, these specific characters are very substantial, and 

 good sj^ecimens of either sex are not hard to identify. 



I have considered that the short apparent sixth segment forms the 

 base of the ovipositor, making the organ three jointed; this basal 

 joint is sometimes so closely united with the following or first long 

 joint that the suture can hardly be made out. 



The genitalia of the male are diificult to spread so that they can 

 be described in detail. I have contented myself with such items as 

 can be seen with comparative ease, and in describing the " forceps " 

 have adopted the terms used in muscoids, where the posterior and 

 anterior (or inner and outer) forceps are usually well marked. I 

 find both these structures quite recognizable in Stylogaster^ but of 

 softer consistency and paler than in Tachinidae; the anterior fold 

 diagonally across under the posterior ones in repose. The apparent 

 seventh segment is the last and principal genital segment, the sixth 

 being very narrow, or in rare cases retracted out of sight. 



Distribution. — Two very distinct species occur in the United 

 States, 1 of which extends into Mexico ; 6 previously described species 

 and 12 here described as new range from tropical Mexico to Brazil, 

 Paraguay, and Bolivia; 5 are from tropical and southern Africa; 1 

 from India ; and 1 from the Philippine Islands. No specimens have 

 been seen or reported from the West Indies. 



Hahits. — Bates, in his famous Naturalist on the River Amazons, 

 first edition, 1863 (vol. 2, p. 365), says in discussing several species 

 of the ant genus Eciton, which march in large columns in the Ama- 

 zon region : 



Tlie armies of all Ecitons are accompanied by small swarms of a kind of two- 

 winged fly, the females of vi'hich have a very long ovipositor and which belongs 

 to the genus Stylogaster (family Conopsidae). These swarms hover with rap- 

 idly vibrating wings at a height of a foot or less from the soil over which the 

 Ecitons are moving, and occasionally one of the flies darts with great quickness 

 toward the ground. I found they were not occupied in transfixing ants, al- 

 though they have a long needle-shaped proboscis, which suggests that conclu- 

 sion, but most probably in depositing their eggs in the soft bodies of insects, 

 which the ants were driving away from their Iiiding plac.-es. These eggs would 



