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-Ay (ippobosea 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 evenif 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 Livus paraplecticus, 
which Linné considers as the cause of the equine disease called in Sweden, 
after the Phellandrium aquaticum, “ Stakra,’ had not the observations of 
the accurate De Geer rendered it doubtful whether the insect be at all con- 
nected 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 agricul- 
ture, is an excellent substitute for the horse (you will directly perceive I 
am speaking of the or, 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 (@. 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.8 He thinks the infliction of the wound is not attended by 
much pain, except where very sensible neryes ave injured, when the 
5 1 Life of General Thomas, 186. 
2 Linn. Jt. Scand. 182. De Geer, y. 227—280, 
% 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 Jarv~@ when hatched burrowed into 
the flesh. ssay on the Bots of Horses and other Animals, p. 47. 
