1 4 



17- 



ORDER DIPTERA: THE BRACHYCERA 139 



f First and 2nd segments of antennae short = 1 5. 



I First and 2nd segments of antennae long Chrvsops, Meigen. 



("Second segment of abdomen unusually large, spurs of tibis small 

 IS- "! Pronopes, Loew (Cape of Good Hope). 



vSecond segment of abdomen, etc., not as in Pronopes = 16. 



rFace concave in the middle 

 16. A Rhinomyza, Wied. (Cape of Good Hope and Java). 



I Face not concave in the middle =17. 



Wings with ist posterior cell open 



SiLVlUS, Meigen (subgenus Silvius), 

 Wings with 1st posterior cell closed 



Silvius, Meigen (subgenus Esenbeckia, Rond., Brazil). 

 Third segment of antenna with an acute spine 



Gastroxides, Saunders (India). 



Family Leptid^e (XeTTTo'j = slender). The Leptzdce dire a. 

 widely distributed family of dull-coloured flies showing 

 considerable diversity of form. Many have a slender, 

 tapering body, and long, slender legs, and some of these 

 slender species are almost gnat-like in appearance. The 

 form of the antenna is particularly varied ; it may consist of 

 3 simple segments, either with or without a terminal or 

 dorsal bristle ; or of 3 segments with the 3rd com- 

 pound as in TabanidcB ; or it may be coarsely nematocerous. 

 The empodia are expanded. The wings are often blotched, 

 and the venation is commonly like that of the Tabanidcz ; but 

 the squams are small or vestigial. 



Some Leptidae are predatory on other insects, and a few 

 species (European and American) are known to suck blood. 

 The larvae are predaceous and those of one genus ( Vermileo) 

 make pitfalls in sand like the ant-lions. 



Austen cites 4 blood-sucking species of Lepiidce, namely : 

 Symphoromyia in America, Leptis scolopacea and strigosa in 

 France, and Trichopalpus obsciirus in Chili. 



In Symphoromyia the antennae are composed of 3 segments 

 with an arista, the 3rd segment being kidney-shaped ; the 

 proboscis is short ; the front tibiae have no terminal spurs, 

 and the hind tibiae have a single spur ; and the wing venation 

 is like that of TabanidcB, with the anal cell open. 



Leptis differs from Symphoromyia in not having the 3rd 

 antennal segment kidney-shaped, and in having two spurs on 

 the hind tibize. 



In TricJiopalpus the proboscis is elongated. 



