1074 



PRACTICE OF AGRICULTURE. 



Part III. 



761 



mouth they have a proboscis, sometimes contained in a vagina, and sometimes furnished 

 at its sides with two palpi, but no maxilla. Their eyes are reticulated and large. The 

 females, in general, lay eggs, but some are viviparous ; the larvae of the insects of this 

 order are as various in their appearance as the places in which they are bred. In general 

 they do not cast their skins, but change into a pupa state. Flies, strictly so called, gad- 

 flies, and gnats belong to this order. 



6906. The gad-fly {(Estrus) is a genus exceedingly 

 troublesome to horses, cattle, and sheep, in the skins 

 of which they deposit their eggs, {fig. 761 a), which 

 soon change into larvaj {b), that feed under the skin 

 of living animals, and often line the stomachs ol 

 horses under the name of bots {Clarke, in Linn. 

 Trans, vol. iii.); the larvae are soft, smooth, annu- 

 late, without feet, and in most species furnished 

 with hook-like appendages : the chrysalis (c) differs 

 little in fornj from the larvae. The O. bovis (rf) in. 

 tests oxen ; O. hsemorrhoidalis {e), horses ; and O. ovia, 

 sheep. 



6907. The crane-fly {Tipula) resembles the gnat, it 

 feeds on various substances ; the larvae are without 

 feet, soft and cylindrical ; pupa cylindrical, horned ; 

 some species reside amongst the roots of aquatic vege- 

 tables, others amongst grass, as that well-known pest, 

 the wire-worm ; but by far the greater number are 

 aquatic. The perfect flics are found in abundance 

 in the autumnal months. The T. oleracea, or long- 

 legs, feeds on the roots of the cabbage ; and the 

 T. crocato {fig. 762 a) and other species inhabit 

 meadows, and are common from spring to autumn . 

 The wheaUfly {T. tritici, h), twelve of which have 

 been observed at one time laying their eggs in a 



single ear of wheat, would soon become of serious injury to mankind, were not their race kept within 

 due bounds by several natural enemies, particularly the ichneumon tipulae. The well-known gafier long- 

 legs, so frequently seen in houses in the autumnal evenings, flying about the flame of the candles, and 

 often perishing in the blaze, is the T. rivosa (c), one of the largest species of the genus. The eggs of the 

 wheat-fly (d) are very small : when magnified they appear roundish {e) ; the larvae also {J ), and the 

 perfect insect (6), to be studied, should be magnified {g, h). 



6908. The fly genus [Musca] presents many curious species. The common flesh-fly {M. vonnioria, fig. 

 763 a) deposits its eggs on the meat in our shambles and larders. These eggs {b) speedily become larvae (c) 

 are soon full grown {d), change to the chrysalis state {e), ^fiS 



and in a month the fly appears {a). The rapid multipli- 

 cation of the fly is thus calculated by Leuwenhoeck. 

 " Let us suppose, that in the beginning of June there 

 shall be two flies, a male and a female, and the female 

 shall lay 14-1 eggs, which eggs, in the beginning of July, 

 shall be changed into flies, one half males and the other 

 half females, each of which females shall lay the like 

 number of eggs; the number of flies will amount to 

 10,000 : and, supposing the generation of them to proceed 

 in like manner another month, their number will then 

 be more than 700,000, all produced from one couple of 

 flies in the space of three months." The Hessian fly 

 {M. pupilionis, f) is very destructive to wheat and rye, 

 and has occasionally been a source of great alarm to our 

 agriculturists. The cheese-fly (3/. 77?//m,/)f), well known 

 to housewives under the name of hopper, deposits its eggs 

 in the crevices or holes of the cheese, whence those nu- 

 merous maggots {h), that so much amuse us by their 

 agility and surprising leaps. One of these insects, not a 

 quarter of an inch in length, has been known to leap 

 out of a box six inches deep. The chrysalis (?) is straight 

 and crusty. 



C909. The gnat {Culex) is frequently in the neighbor- 

 hood of waters and marshy places. In southern regions 

 there is a large species, which is known by the name of 

 musquito. Its bite is painful, raising a considerable de- 

 gree of inflammation, and its continual piping note is exceedingly irksome where it abounds, especially 

 during the night. When it .settles to inflict the wound and draw the blood, it raises its hind pair of feet. 

 In liapland, the injuries the inhabitants sustain from it are amply repaid by the vast number of water- 



