INDIRECT INJURIES CAUSED BY INSECTS. 115 



them in a particular district in India in so tremendous a manner as to 

 cause incurable cancers, which finally destroy them.^ — But of all the 

 insect tormentors of these useful creatures, there is none more trying to 

 them than the forest-fly (Hiypohosca equina). Attaching themselves to 

 the parts least covered with hair, particularly under the belly between the 

 hind legs, they irritate the quietest horse, and make him kick so as often 

 to hazard the safety of his rider or driver. This singular animal runs 

 sideways or backwards like a crab ; and, being furnished with an unusual 

 number of claws, it adheres so firmly that it is not easy to take it off; 

 and even if you succeed in this, its substance is so hard, that by the 

 utmost pressure of your finger and thumb it is difficult to kill it ; and if 

 you let it go with life, it will immediately return to the charge. — Amongst 

 the insect plagues of horses, I should also have enumerated the larva of 

 Lixiis paraplecticus , which Linne considers as the cause of the equine 

 disease called in Sweden, after the P hellandrium aquaticum, " Stdkra" 

 had not the observations of the accurate De Geer rendered it doubtful 

 whether the insect be at all connected with this malady.^ 



Another quadruped contributing greatly to our domestic comfort, from 

 which we derive a considerable portion of our animal food, and which, 

 on account of its patient and laborious character when employed in agri- 

 culture, is an excellent substitute for the horse, (you will directly perceive 

 I am speaking of the ox, whether male or female,) is also not exempt 

 from insect domination. At certain seasons the whole terrified herd, with 

 their tails in the air, or turned upon their backs, or stiffly stretched out in 

 the direction of the spine, gallop about their pastures, making the country 

 re-echo with their lowings, and finding no rest till they get it into thew'ater. 

 Their appearance and motions are at this time so grotesque, clumsy, and 

 seemingly unnatural, that we are tempted rather to laugh at the poor 

 beasts than to pity them, though evidently in a situation of great terror 

 and distress. The cause of all this agitation and restlessness is a small 

 gad- or bot-fly ((E. Bovis) less than the horse-bee, the object of which, 

 though it be not to bite them, but merely to oviposit in their hides, is not 

 put Into execution without giving them considerable pain. 



When oxen are employed in agriculture, the attack of this fly is often 

 attended with great danger, since they then become perfectly unmanage- 

 able ; and, whether in harness or yoked to the plough, will run directly 

 forward. At the season when it infests them, close attention should be 

 paid, and their harness so constructed that they may easily be let loose. 



Reaumur has minutely described the ovipositor, or singular organ by 

 which these insects are enabled to bore a round hole in the skin of the 

 animal and deposit their eggs in the wound. The anus of the female is 

 furnished with a tube of a corneous substance, consisting of four pieces, 

 which, like the pieces of a telescope, are retractile within each other. 

 The last of these terminates in five points, three of which are longer than 

 the others, and hooked : when united together they form an instrument 

 very much like an auger or gimlet ; only, having these points, it can bite 

 with more effect.^ He thinks the infliction of the wound is not attended 



> Life of General Thomas, 186. « Linn. It. Scand. 182. De Geer, v. 227—230. 



3 Mr. Clark, however, is of opinion that the gad-fly does not pierce the skin of the 

 aninaal, but only glues its eggs to it ; the young larvae when hatched burrowed into the 

 flesh. Essay on the Bots of Horses and other Animals, p. 47. 



