94 OUTLINES OF ENTOMOLOGY. 



The Eobber-flies (AsiLiD^)have long, slender bodies and wings, and 

 spiny, long, stout legs. The beak is short bnt strong, and the under 

 lip well developed. The eyes are almost globular, and the antennae 

 short, often tipped with a bristle. The body is usually hairy, varying 

 in length from one to two inches, and tapers toward the tip. The colors 

 are mostly black and white, though some species have the thorax 

 clothed with yellow hairs. In their perfect state, the Robber-flies are 

 fierce and greedy cannibals, especially destructive to the honey-bee, of 

 which one species has been known to kill and suck the vital juices of 

 more than one hundred and forty in a day, according to Dr. Packard. 

 They sometimes make amends, however, by preying on the Cabbage 

 butterfly, though I fear this has not yet become a very general habit. 

 The larvfe live in the ground, and those that have been studied have 

 fed upon roots. 



The Bee-flies (Bombylid^) resemble small Humble bees in their 

 thick, hairy bodies. They are very swift on the wing, and are often 

 found on flowers, from which they extract nectar with the long pro- 

 boscis. The larviie are parasitic on bees and on the eggs of locusts 

 (grasshoppers). 



In the Sub-Order Cyclorapha we find a large number of 

 families of flies whose larvae are parasites or scavengers and a few 

 that feed on vegetation, among which are some common gall-makers 

 also some that live in water. The transformations take place either 

 underground or on the surfaces upon which the larvse fed — the larval 

 skin thickening and hardening into an oblong case, within which the 

 soft, white pupa is formed. The flies always come out through around 

 hole on the top. They usually have rather short, thick bodies, broad 

 heads and short antennsB, ending in a bristle. The following families 

 contain the species that are most directly beneficial or injurious to man : 

 Syrphus flies (Syrphid^). See Plate of Orders.) This is a group of 

 handsome flies, ranging in size from small to medium (having a body 

 length of from one-fifth to one-half inch). The colors are often arranged 

 in bright bands, giving the insects quite a wasp-like appearance. The 

 front of the face has no groove for the reception of the antenna?, which 

 have the last joint much thickened just back of the bristle. The 

 larvae are legless and headless, leech-like creatures, which do us great 

 service in destroying all kinds of plant-lice ( AphididceJ, and may almost 

 always be found in the colonies of the latter, which they very rapidly 

 exterminate. The great majority of the beneficial species are found in 

 the genus Syrphus. Their transformations are very easily observed, as 

 they are hardy and develop rapidly. 



