150 INDIRECT INJURIES CAUSED BY INSECTS. 



ance and motions are at tliis time so grotesque, clumsy, 

 and seemingly unnatural, that we are tempted rather to 

 laugh at the poor beasts than to pity them, though evi- 

 dently in a situation of great terror and distress. The 

 cause of all this agitation and restlessness is a small gad- 

 fly [CE. Bovis), less than the horse-bee, the object of 

 which, though it be not to bite them, but merely to ovi- 

 posit in their hides, is not put into execution without 

 giving them considerable pain. 



When oxen ai'fe 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 dii-ectly for- 

 ward. At the season when the CEstrus infests them, 

 close attention should be paid, and their harness so con- 

 structed that they may easily be let loose. 



Reaumur has minutely described the ovipositor, or sin- 

 ffular organ bv 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 ginilet; only, having these 

 points, it can bite with more effect^. He thinks the in- 

 fliction of the wound is not attended by much pain, ex- 

 cept where very sensible nerves are injured, when the 



* Plate XVI. Fig. 3. Mr. Clark, however, is of opinion tliat the 

 Qlstrus does not pierce the skin of the animal, but only glues its eggs 

 to it. Essay on the Bots of Horses and other Animals, p. 4/. 



