16 INSECTS INJURIOUS TO VEGETATION. 



viviparous flesh-flies {SarcophagcB and Cynomi/icE), whose maggots 

 live in flesh, the cheese-fly {Piophila), the parent of the well-known 

 skippers, and a few others that in the larva state attack our household 

 stores. Some flies are entirely harmless in all their states, and many 

 are eminently useful in various ways. Even the common house-flies, 

 and flesh-flies, together with others, for which no names exist in 

 our language, render important services by feeding while larvse upon 

 dung, carrion, and all kinds of filth, by which means, and by simi- 

 lar services, rendered by various tribes of scavenger-beetles, these 

 offensive matters speedily disappear, instead of remaining to decay 

 slowly, thereby tainting the air and rendering it unwholesome. 

 Those whose larvse live in stagnant water, such as gnats {CulicidcE), 

 feather-horned gnats {Chironomus, &c.), the soldier-flies {Strati- 

 omyadce), the rat-tailed flies {Helophilus, &c. &c;.), tend to prevent 

 the water from becoming putrid, by devouring the decayed animal 

 and vegetable matter it contains. The maggots of some flies {Myce- 

 tophilcE and various Muscadce) live in mushrooms, toadstools, and 

 similar excrescences growing on trees; those of others (Sargi, 

 Xylophagidce, AsilidcB, TherevcB, Milesice, XylotcB, Borbori, &;c. 

 djc), in rotten wood and bark, thereby joining with the grubs of 

 certain beetles to hasten the removal of these dead and useless sub- 

 stances, and make room for new and more vigorous vegetation. 

 Some of these wood-eating insects, with others, when transformed to 

 flies {AsilidcB, RhagioriidcB, DolichopidcB, and Xylophagidce), prey 

 on other insects. Some (Syrphidce), though not predaceous them- 

 selves in the winged state, deposit their eggs among plant-lice, upon 

 the blood of which their young afterwards subsist. Many {Cono- 

 pidcB, excluding Stomoxys, TachincB, Ocypterce, PhorcB, &c.) lay 

 their eggs on caterpillars, and on various other larvae, within the bodies 

 of which the maggots hatched from these eggs live till they destroy 

 their victims. And finally others {AnthracidcB and Volucellce), drop 

 their eggs in the nests of insects, whose offspring are starved to death, 

 by being robbed of their food by the offspring of these cuckoo-flies. Be- 

 sides performing their various appointed tasks in the economy of nature, 

 flies, and other insects,subserve another highly important purpose, for 

 which an all-wise Providence has designed them, namely, that of fur- 

 nishing food to numerous other animals. Not to mention the various 

 kinds of insect-eating quadrupeds, such as bats, moles, and the like, 

 many birds live partly or entirely on insects. The finest song-birds, 

 nightingales and thrushes, feast with the highest relish on maggots of 



