360 INSECTS. 



Of the four families in which the pupse remain within 

 the altered and cocoon-like larva skin, the first is Syr- 

 phidse. 



This is a very large family, consisting of no less than 

 thirty-one genera, and containing many large Flies, 

 rendered conspicuous by their bright and well-marked 

 colouring, their vigorous flight, and their constant pre- 

 sence during spring, summer, and autumn. Not only in 

 fields, lanes, and woods, but in our gardens too, the 

 motion of their bright and glancing wings, their musical 

 hum, and their evident enjoyment of the sunshine and the 

 flowers, are no small ingredients in the general brightness. 



They are, almost without exception, pure flower-lovers 

 in their perfect state. In their earlier stages some of 

 them are useful servants to the gardeners, for while a few, 

 feeding on bulbous roots, &c., are known as injurious to 

 cultivated plants, the larvae of the genus Syrphus and 

 others are highly beneficial to them, living entirely upon 

 Aphides. Some, less praiseworthy, are parasitic in the 

 nests of Humble Bees and of Wasps. Others live in 

 rotten wood, cow-dung, and fungi ; while the larvae in the 

 genera Eristalis and Helophilus are aquatic. 



The "Drone-fly," of which the aquatic larva is described 

 p. 47, is Eristalis tena#(Pl.XV., fig. 3). This, and some 

 other large stout-bodied Flies in this genus and Helophi- 

 lus,* must be familiar to every lover of the garden from their 

 habit of holding revels in the blossoms of the Michaelmas 

 daisy. They make a peculiarly loud and musical hum on 



* These two genera much resemble each other, and may be known by 

 the form of the subapical cell, into the middle of which (see fig. 22, p. 49) 

 the cubital nerve makes a sudden dip. In Eristalis the subcostal and 

 radial nerves meet before reaching the margin ; in Helophilus ending 

 separately in the margin. 



