ORDER DIPTERA. 



129 



often prolonged to a point. Front on each side with two 

 bristles, one of which i> situated more above and in front, the otber 

 below and exteriorly. Border ol the moutb with n<> 

 Clypeua none or rudimentary. Pro never thickened. <>nl\ 



the middle tibia; with spurs; all the tibiae without an erect bristle 

 on the outer Bide before the lip. Ovipositor horny, consistin 

 three elongated retractile segments like the drawers of a telescope, 

 the last of which ends in a simple point. Trypeta Jtoreacentia Linn. 

 Europe and North America. 



Family Ortalidae. — Venation of the \\ ings complete; auxiliary vein 

 separated from the first longitudinal vein, and running to the border 

 of the wing in the usual way, under an acute angle, and remaining 

 perfectly distinct in its whole length; third longitudinal vein 

 erally with coarse hairs; two posterior basal cells large, and the 

 ward one frequently prolonged in an acute angle. Front with 

 bristles on the upper part only; do vibrissas at the border of the 

 mouth; clypeus commonly ven much developed, and proh< 

 often very much thickened. .Middle tibiae alone witb spurs; 

 tibiae with an erect bristle on the exterior side before the tip. 

 Ovipositor of the female rather flattened and horny, consisting of 

 three elongated segments, forming three drawers like the 

 telescope, and ending in a simple point. , ' data \\ 



ZWfc \\i. d. 



Fio. 151.— Tritoxaflexa, onion fly, an. I ra . 



Family Micropezida?. Body long and slender; legs short; front 

 with bristles near the crown. Cahbata antennij Say. 



Family Psilidx. Body slender, face receding, mouth small. 

 Psila bicolor Meig. Europe and North America. 



Family Soiomysida front with two bristles, one behind the 

 other, on the side lief.. re the vertical bristles; middle tibia 

 greater number of bristles at the tip. fi 



Europe and North America. 



Familj HelomyiicUB.— Front bristly on the upper half onlj . all the 

 tibiae spurred. Helomym tapiealis Loew. 



Family Cordylnrids. — Venation of the wings con 

 terior basal cells of considerable si/e: auxiliary v< in v si pa: 



from the first longitudinal vein, which is hare." El ' the 



