120 



INDIRECT INJURIES CAUSED BY INSECTS. 



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 unmanageable ; 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. 



Keaumur 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 by much pain, except 

 where very sensible nerves are injured, when the animal, ap- 

 pearing to be seized with a kind of frenzy, begins to gambol, 

 and run with such swiftness that nothing can stop it. From 

 this semblance of temporary madness in oxen when pursued 

 and bored by the CEstrus, the Greeks applied the term to 

 any sudden fit of fury or violent impulse in the human species 

 calling such ebullitions an CEstrus. The female fly is observed 

 to be very expeditious in oviposition, not more than a few 

 seconds ; and while she is performing the operation, the animal 

 attempts to lash her ofl", as it does other flies, with its tail. 

 The circular hole, made by the auger just described, always 

 continues open, and increases in diameter as the larva increases 

 in size ; thus enabling it to receive a sufficient supply of" air 

 by means of its anal respiratory plates, which are usually near 

 the orifice. — But though these insects thus torment and 

 terrify our cattle, they do them no material injury. Indeed 



1 Mr. Clark, however, is of opioion 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 Bats of Horses and other Animals, p. 47 



