472 THE STUDY OF INSECTS, 



often mistaken for it. This is the Drone-fly, Eristalis tenax 

 (E-ris'ta-lis te'nax). It is common about flowers. The 

 larva lives in foul water, where it feeds on decaying vegeta- 

 ble matter ; it is of the form known as ** rat-tailed," which is 

 described below. 



The larvae of the genus Volucella (Vol-u-ceria) are pre- 

 daceous, living in the nests of bumblebees and of wasps 

 {Vespd), and feeding upon their larvae. Some of the species 



in the adult state very closely re- 

 semble bumblebees. 



The larvae of the genus Micro- 

 „^. , , , , ^^/^(Mic'ro-don) are hemispherical, 



Fig. 575. — Microdon^ adult and ^ ^ ^ 



^arva. slug -like creatures (Fig. 575), 



which resemble mollusks more than ordinary maggots ; they 

 are common in ants' nests. 



The larvae of several species that live in water as well as 

 some that live in rotten wood are known as rat-tailed mag- 

 gots on account of a long, tail-like appendage, with which 

 the hind end of the body is furnished. This is a tube, like 

 that of a diver, which enables the insect to obtain air when 

 its body is submerged beneath several inches of water or de- 

 caying matter. This tube being telescopic can be lengthened 

 or shortened as the insect may need it ; and at its tip there 

 is a rosette of hairs, which, floating on the surface of the 

 water, keeps the tip from being submerged. The larva has 

 on the ventral side of its body several pairs of tubercles 

 armed with spines, which serve as prolegs. 



Among the more common members of this family are 

 the yellow-banded species belonging to the 

 genus Syrphus (Syr'phus) (Fig. 576). The larvae 

 of these live in colonies of Aphids, and do much 

 good by destroying these pests. 



This family is a very large one ; nearly or 

 quite two thousand species being known. In P^us, 

 his monograph of the species of America north of Mexico, 



