MANUAL OF NATURAL HISTORY. 251 



duals the Flies muster in very great force. They 

 surround us, in some form or other, all the year 

 throughout ; and, during the hot weather the whole 

 atmosphere seems filled with the humming sound of 

 their wings. The Flies, in their perfect state, hover 

 over flowers, and sip honey, like the Bees ; but in 

 their larval condition, their habits are very varied. 

 Some among them prefer a vegetable diet, like the 

 Mycetophilce, which are found on fungi ; some, like 

 the Syrphidce, feed upon the plant-lice, and help to 

 keep those injurious hordes in wholesome check. 

 The Volucellce deposit their eggs in the nests of 

 the Humble-Bees, that their young may take advan- 

 tage of the food there stored up ; others, as the Gad- 

 Flies, lay their eggs in the skins of Ruminating ani- 

 mals, on which the larvae subsist ; while some devour 

 putrescent bodies dissolved in water, as the Gnat 

 and Mosquito. Some Flies are carnivorous and pre- 

 datory in their perfect state, as the Asilidce, which 

 seize other insects, and suck their blood ; others feed 

 on decaying timber; others on bulbs, as the Eristalis 

 Narcissi and the Scatophaga Ceparum. The pupi- 

 parous Forest-Flies nourish their offspring in a kind 

 of marsupial pouch, and the Flesh-Flies lay their eggs 

 on dead bodies, which their larvae, when hatched, 

 very soon consume. 



XI. ORDER,.— Flies (Diptera). 



Mouth suctorial, with a fleshy proboscis enclosing 

 several lancet-like organs (formed by the tongue 

 jaws and mandibles) ; labial palpi obsolete or none ; 



M 5 



