DIPT ERA 



3°9 



Family Therevid^e 

 The Stiletto-flies 



With the flies of this family the head is transverse, being nearly as 

 wide as the thorax; and the abdomen is long and tapering, suggesting 

 the name stiletto-flies. These flies are small or of medium size; they are 

 hairy or bristly. The antennas are three-jointed; the third segment is 

 simple, and usually bears a terminal style. The legs are slender and 

 bristly; the empodia are wanting. It is a small family. 



The adult flies are predacious; they conceal themselves among the 

 leaves of low bushes or settle on the ground in sandy spots, waiting for 

 other insects, chiefly Diptera, upon which they prey. 



The larvas are long and slender, and the body is apparently composed 

 of nineteen segments. They are found in earth, fungi, and decaying 

 wood. 



Family Scenopinid^e 



The Window-flies 



The window-flies are so-called because the best-known species are 

 found almost exclusively on windows; but the conclusion that these are 

 the most common flies found on windows should not be drawn from this 

 name; for such is not the case. 



These flies are of medium size, our most common species measuring 

 \ of an inch in length. They are usually black, and are not clothed with 

 bristles. The thorax is prominent, and the abdomen is flattened and 

 somewhat bent down, so that the body when viewed from the side 

 presents a humpbacked appearance (Fig. 544). When 

 ^jm^ at rest, the wings lie parallel, one over the other, on the 



(^^ abdomen. The antennas are three- jointed; the first and 



" second segments are short, the third is long and bears 



Fig S44-— neither a style nor an arista (Fig. 54O. 



Scenopwus. J . . r 1 • 1 n ■ Fig de 



1 he larvas, which are sometimes round in dwellings ' i4> ' 

 under carpets or in furniture, are very slender, and are remarkable for the 

 apparently large number of the segments of the body, each of the abdominal 

 segments except the last being divided by a strong constriction. They 

 are also found in decaying wood, and are supposed to be carnivorous. 



547)- 



Family Asilid^e 

 The Robber-flies 



These are mostly large flies, and 

 some of them are very large. The 

 body is usually elongate, with a 

 very long, slender abdomen (Fig. 

 546) ; but some species are quite 

 stout, resembling bumblebees in 

 form and coloring. 



The vertex of the head is hol- 

 lowed out between the eyes (Fig. 

 In this family the proboscis is pointed and does 



Fig. 546. — Erax apica- 

 lis destroying a cotton- 

 worm. (From the Author's 

 Report for 1879.) 



Fig. 547 

 robber-fly. 



— Head of 



