80 INDIRECT INJURIES CAUSED BY INSECTS. 



curable cancers, which finally destroy them. 1 But of all the insect tor- 

 mentors of these useful creatures, there is none more trying to them than 

 the forest-fly (Hippobosca 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 Lixus paraplecticus, 

 which Linne considers as the cause of the equine disease called in Sweden, 

 after the Phellandrium aguaticum, " Stakra" had not the observations of 

 the accurate De Geer rendered it doubtful whether the insect be at all con- 

 nected with this malady. 2 



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 agricul- 

 ture, 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 into the water. 

 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 (CE. 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. 3 He thinks the infliction of the wound is not attended by 

 much pain, except where very sensible nerves are injured, when the 



1 Life of General Thomas, 186. 



2 Linn. It. Scand. 182. De Geer, v. 227230. 



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

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

 the flesh. Essay on the Hots of Morses and other Animals, p. 47. 



