OESTRUS. 
36 \ 
eggs^ are sometimes placed on one horse. The 
Ijorses, when they become used to this fly, and 
find that it does them no injury, as- the Tahani 
and Cojwpes, by sucking their blood, hardly regard 
it, and do not appear at all aware of its insidious 
object. The skin of the horse is always thrown 
into a tremulous motion on the touch of this in- 
sect, which merely arises from the very great irri- 
tability of the skin and cutaneous muscles at this 
season of the yearf, occasioned by the continual 
teasing of the flies, till at length these muscles act 
involuntarily on the slighest touch of any body 
whatever. The inside of the knee is the part on 
wdiich these flies are most fond of depositing their 
eggs, and next to yhis on the side and back part 
of the shoulder, and less frequently on the extreme 
ends of the mane. But it is a fact w’orthy of atten- 
tion, that the fly does not place them promiscu- 
ously about the body, but constantly on those parts 
which are most liable to be licked with the tongue; 
and the ova therefore are always scrupulously 
placed within its reach. The eggs thus deposited 
I at first supposed were loosened from the hairs 
by the moisture of the tongue, aided by its rough- 
ness, and were conveyed to the stomach, where 
they were hatched; but on more minute search I 
do not find this to be the case, or at least only by 
accident; for wdien they have remained on the 
hairs four or five days they become ripe, after 
which time the slightest application of w^armth and 
* Horses sometimes appear to be nearly covered by tJicm. 
f August and September. 
