INDIRECT INJURIES CAUSED BY INSECTS. 151 



animal, appearing to be seized with a kind of phrensy, 

 begins to gambol, and run with such swiftness that no- 

 thing can stop it. From this semblance of temporary 

 madness in oxen when pursued and bored by the QEstrus, 

 the Greeks applied the term to any sudden fit of fury or 

 violent impulse in the human species, calling such ebulli- 

 tions an (Estrus. 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 off, 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 suf- 

 ficient 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 they occasion consi- 

 derable tumours under the skin, where the bots reside, 

 varying in number from three or four to thirty or forty ; 

 but these seem unattended by any pain, and are so far 

 from being injurious, that they are rather regarded as 

 proofs of the goodness of the animal, since these flies 

 only attack young and healthy subjects. The tanners also 

 prefer those hides that have the greatest number of bot- 

 holes in them, which are always the best and strongest 1 . 

 The Stomoxys, and several of the other flies before 

 enumerated, as well as the dog and American ticks, are 

 as prejudicial to the ox as to the horse. One species of 

 Hippobosca I have reason to believe is appropriated to 



a Much of the information here collected is taken from Rcauin. 

 iv. Mem. 12 ; and Clark in Linn. Trans, iii, 289. 



