50 NORTH AMERICAN DIPTERA. 



upper facets larger than the lower ones ; in life usually with 

 green and purple markings. Ocelli absent or present. Pro- 

 boscis projecting, sometimes much elongated; palpi two- 

 jointed, the second joint elongate or thickened. Thorax not 

 very convex above ; scutellum never with tubercles or spines 

 on its border. Abdomen broad, moderately elongate or short, 

 never slender or constricted ; composed of seven segments ; 

 genitalia never prominent. Legs moderately stout, the 

 tibiae sometimes much dilated ; middle tibiae always with 

 spurs at the tip ; tarsi with three membranous pads at the 

 tip (the empodia developed pulvilliform). Tegulse always 

 of considerable size. The marginal vein encompasses the 

 entire wing; two submarginal and five posterior cells present ; 

 basal cells all elongate, the anal cell closed at or near the 

 margin of the wing. Species never very small, often among 

 the largest of the order, never thickly pilose, and wholly 

 without bristles on body or legs. 



This family includes the flies commonly known as horse- 

 flies, and is widely distributed over the world. About four- 

 teen hundred species are known, of which more than one 

 hundred and fifty are from North America. Many of the 

 species are conspicuous for their large size, though the greater 

 number are of moderate size, but none are small. Most of 

 them love the bright sunshine, though the smaller forms are 

 more usually found about shady places near the border of 

 woods, appearing on sunshiny days. The female alone is 

 blood-sucking in habit ; the males are much more rarely met 

 with, and will be caught usually in sweepings of meadow- 

 lands, on flowers, etc. Their power of flight is remarkable, 

 moving as rapidly as can a horse. Their bites, though pain- 

 ful enough, do not seem to cause the same irritation as those 

 of the mosquitoes and midges. When no better food offers, 

 the females will, like the males, seek the juices of plants and 

 flowers. 



The spindle-shaped brown or black eggs of the Tabanidee 



