14 INSECTS INJURIOUS TO VEGETATION. 



animals, goading the latter sometimes almost to madness by their severe 

 and incessant punctures. The winged horse-ticks (Hippohoscce)^ the 

 bird-flies [Ornithomyicv) ^ the wingless sheep-ticks (MeJophagi), and the 

 spider-flies {Nyclerihicp)^ and bee-lice {Br aula) ^ which are also desti- 

 tute of wings, are truly parasitical in their habits, and pass their whole 

 lives upon the skin of animals. Bot-flies, or gad-flies [(Eslridce)^ as 

 they are sometimes called, appear to take no food while in the winged 

 state, and are destitute of a proboscis ; the nourishment obtained by 

 their larvEe, which, as is well known, live in the bodies of horses, cattle, 

 sheep, and other animals, being sufficient to last these insects during the 

 rest of their lives. Some flies, though apparently harmless in the winged 

 state, deposit their eggs on plants, on the juices of which their young 

 subsist, and are oftentimes productive of immense injury to vegetation ; 

 among these the most notorious for their depredations are the gall-gnats 

 {Cecidonujia;), including the wheat-fly and Hessian fly, the root-eating 

 maggots of some of the long-legged gnats {Tipulce), ihosc of the flower- 

 flies (Ant Jio7nyicp), and the two-winged gall-flies and fruit-flies {Ortali- 

 des). To this list of noxious flies are to be added the common house- 

 flies {3Iiisccr), which pass through the maggot state in dung and other 

 filth, the blue-bottle or blow-flies, and meat-flies (Lucilice and Calli- 

 phorcr), together with the maggot-producing or viviparous flesh-flies 

 (Sarcophago' and Cyno?nyice), 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 larva? upon dung, carrion, and all kinds of 

 filth, by which means, and by similar 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 larvce live in stagnant water, such as gnats 

 (Culicido'), feather-horned gnats {Chirononms, &c.), the soldier-flies 

 (Stratiomyadcr) , the rat-tailed flies (Helophilus, &c. &c.), tend to pre- 

 vent the water from becoming putrid, by devouring the decayed animal 

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

 philce and various Muscada') live in mushrooms, toadstools, and similar 

 excrescences growing on trees; those of others (Sargi, XylophagidcB^ 

 Asilida>, Therevcp, Milesicp, XyJotcp, Borbori, &c. &c.), in rotten wood 

 and bark, thereby joining with the grubs of certain beetles to hasten the 



