840 



AN INTRODUCTION TO ENTOMOLOGY 



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

 6 mm. in length. They are usually black, and are not clothed with 

 bristles. The thorax is prominent, and the abdo- 

 men is flattened and somewhat bent down, so 

 '^SBto W\ ^^^^ ^^^ body when viewed from the side presents 

 (^^ W% a hump-backed appearance (Fig. 1083). When at 

 '^ mm rest, the wings lie parallel, one over the other, on 



the abdomen; when in this position they are very 

 inconspicuous. There are three ocelli. The an- 

 tennae are three-jointed; the first and second seg- 

 ments ai e short, the third is long and bears neither 

 a style nor an arista (Fig. 1084). 

 The venation of the wings is represented by Figure 1085. The 

 radial sector is three-branched; cells Mi and M3 are both obliterated 

 by the coalescence of the veins that bound them ; the first anal cell is 

 closed at a considerable distance before the margin ; and cell R is much 

 longer than cell 2d M. 



The larvae, which are sometimes found in dwellings under carpets 

 or in furniture, are very slender, and are remarkable for the appar- 

 ently large number of the segments of the body, each of the abdom- 



Fig. 1083.— 



Scenopi- ^. 



nus. Fig- 



1084 



Fig. 1085. — Wing of Scenopinus. 



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

 They are also found in decaying wood, and are supposed to be carniv- 

 orous. 



The family is a very small one. The most common species is 

 Scenopinus Jenestrdlis. 



Family ASILID^ 

 The Robher-Flies 



These t^re mostly large flies, and some of them are very large. The 

 body is usually elongate, with a very long, slender abdomen (Fig. 

 1086); but some species are quite stout, resembling bumblebees in 



