26 HISTORY OF INSECTS. 



The opinions respecting the breeze-fly of the horse, or lot 

 as it is usually termed, as to the benefit or injury derived 

 from it, are very opposite ; some observers go so far as to 

 assert that the larvae occasionally completely perforate the 

 stomach of the horse, causing disease, pain, and even 

 death ; others regard them as perfectly innocuous ; and 

 one author, whose careful and laborious investigations en- 

 title his opinions to the greatest respect, believes the effect 

 of bots to be salutiferous rather than otherwise : this author 

 is Mr. Bracy Clark, and from his masterly essay the fol- 

 lowing particulars are extracted. 



The female fly in approaching the horse for the purpose 

 of oviposition, canies her body nearly upright in the air, 

 the protruded ovipositor being curved inwards and up- 

 wards. Suspending herself for a few seconds before the 

 part of the horse on which she intends to deposit the egg, 

 she suddenly darts upon it, and leaves the egg adhering 

 to the hair : she hardly appears to settle, but merely touches 

 the hair with the egg held out on the extreme point of the 

 ovipositor (see fig. /), the egg adhering by means of a 

 glutinous liquor with which it is covered. She then 

 leaves the horse at a small distance, prepares a second 

 egg, and, poising herself before the part, deposits it in the 

 same way : the liquor dries, and the egg becomes firmly 

 glued to the hair. This is repeated till four or five hun- 

 dred eggs are sometimes placed on one horse. The skin 

 of the horse is usually thrown into a tremulous motion on 

 the touch of the insect, which merely arises from the very 

 great irritability of the skin and cutaneous muscles at this 

 season of the year, occasioned by the heat and continual 

 teazing of the flies, till at length these muscles appear to act 

 involuntarily on the slightest touch of any body whatever. 



The fly does not deposit her eggs at random on the 

 horse's body, but selects those parts which are most likely 



