259 
The insects which clo not themselves feed upon our cattle, but 
simply infest them for the purpose of depositing their eggs in some 
convenient place or other upon their bodies, are in no instance that 
I recollect provided with an increased development of the mouth 
organs ; on the contrary, the CEstrides are either entirely destitute of 
a mouth, or have only very small rudiments of some of the ordinary 
parts of the mouth, so as to be entirely unfitted for biting or wound¬ 
ing cattle. The effects however which some of these species pro¬ 
duce are as annoying as those caused by the bites of the Tabani. The 
female fly of the common horse hot, CEstras Equi, it is true, instils 
no dread into the horse round which she is intently engaged in flying, 
depositing her eggs here and there in particular spots where the horse 
is certain to lick the hairs, by which means the eggs are introduced 
into the mouth and pass into the stomach. So little indeed is the 
horse affected by the presence of this insect, that I have often stood 
close to one rouud which the CEstrus Equi has been flying, until the 
latter has come within reach of my hand, when I have caught it with- 
out trouble. Another species, (Estrus hcemorrhoidalis, is however 
much more troublesome ; depositing her eggs on the lips of the horse, 
and producing in her endeavours to effect this such an excessive titil- 
lation, as to cause great uneasiness to the horse, which tosses its head 
about to drive off its enemy, gallops about, and as a last resource 
takes refuge in some neighbouring water, where the (Estri never fol¬ 
low it. The same kind of effect is also produced in rein deer by the 
CEstrus Tarandi *, and in oxen by another species of CEstrus , CEst. 
Boris, respecting which however much difference of opinion has arisen. 
At certain seasons, the whole terrified herd, with their tails in the air, 
or turned upon their backs, or stiffly stretched out in the direction of 
the spine, gallop about the pastures, finding no rest till they also get 
into the water. This (Estrus is asserted by some writers to make a 
strong humming noise, and hence it has been supposed that the herd 
of cattle are alarmed at the noise; but this must surely be an incor¬ 
rect conjecture, as the (Estri , if they make any hum at all, are far out¬ 
stripped in this respect by many other insects which instil no dread 
into oxen. Neither are they alarmed in consequence of being sub¬ 
jected to the same kind of attack upon so sensitive apart as the lips, 
as is the case with the horses attacked by CEstrus hcemorrhoidalis. It 
is however asserted by some writers, that the dread is produced by 
the pain inflicted by the (Estrus in depositing her eggs, her ovipositor 
being represented as constructed like an auger or gimlet, only having 
several longer points it can wound with more effect. When it is stated, 
however, that the female CEstrus Boris does not occupy more than a 
few seconds in depositing each egg, we may fairly doubt whether, with 
her long, fleshy, tubular ovipositor, she has been able to pierce the 
hide of an ox; or whether, as Mr. Bracy Clark suggests, she only 
* At the present time (April 1851) some of the rein deer in the Gardens of the 
Society, which were imported last autumn from Lapland, are infected to a re¬ 
markable extent with the tumours of this species; there must, I think, be from fifty 
to a hundred tumours on one of these animals. 
