The Two-winged Flies 327 



found the counts averaged fifteen Bibios per square foot; and there were 

 here in one place forty acres of such Bibio territory." 



Two families of nematocerous flies are not included in the key, and have 

 not heretofore been referred to. They are the Orphnephilidae, of which but 

 a single species is known in this country, viz., Orphnephila testacea, a small 

 reddish-yellow fly without hairs or bristles on its body, and with short antennas 

 apparently composed of two segments, but really of ten, the apparent first 

 segment being made up of three closely 

 opposed segments, and the second of seven. 

 The fly itself is found along stream banks, 

 but nothing is known of its immature stages. 



The other family, Rhyphidae, or false crane- . 



,,. , , . ,,. , FIG. 456. Diagram of wing of 



flies, is represented in this country by two Rhyphus sp. 



genera containing several species. The flies 



are small and slender, with broad spotted wings veined in a character- 

 istic way (Fig. 456). The larvae of Rhyphus are worm-like, legless, naked, 

 more or less transparent, with snake-like movements. They live in water, 

 brooks, pools, or puddles, or in rotting wood, hollow trees, or manure. 



SECTION BRACHYCERA. 



The Brachycera, or flies with "short horns," i.e., short thick antennas 

 composed of few segments, in contrast with the many-segmented antennae, 

 usually slender and long, of the Nematocera, are separable into three groups 

 of families, as indicated in the key on page 303, based on a further analysis 

 of the structural character of the antennae. These groups are, first, one includ- 

 ing flies in which the antennae are composed of more than five segments but 

 with all those beyond the second coalesced to form a single compound 

 segment, bearing more or less distinct annulations indicating the component 

 subsegments; second, one including flies having antennae made of four or 

 five distinct segments; and third, and by far the largest, one including flies 

 with but three segments in the antennae. 



In the first group are two families and part of a third; this division of a 

 family indicating plainly the artificial character of the subdivision into 

 groups, the subdivision being merely convenient. The three families may be 

 distinguished as follows: 



The branches of the radial vein (see Fig. 460) crowded together near the costal (front) 



margin of the wing (Soldier-flies.) STRATIOMYID^E. 



Venation normal. 



Alulets, i.e., little whitish wing-like membranous flaps at the base of the true wings, 



large (Horse-flies.) TABANID^E. 



Alulets small (Snipe-flies.) LEPTID.E (in part). 



