000 
evacuated with the dung ‘The ejected maggot 
seeks a place of shelter, buries itself in the 
ground, and contracts and changes into a chry- 
salis; the insect, in this latter form, resembles 
the larva in shape, but is more rigid, and has a 
reddish-brown colour; and, after lying for a few 
weeks inactive, it escapes by the narrow end of 
the pupa-case, and assumes its final form of an 
imago or a fly. 
Many stern opinions have been entertained as 
to excessive injuries done to the horse by the 
great common bot which we have described, and 
as to the desirableness of using strong medi- 
| cinal means for destroying the insect; but all 
| such opinions, in the matured judgment of mo- 
| dern farriers, are very nearly without foundation. 
“The bots,’ says Mr. Youatt, “ cannot, while 
they inhabit the stomach of the horse, give the 
| animal any pain, for they have fastened on the 
cuticular and insensible coat. They cannot 
stimulate the stomach and increase its digestive 
| power, for they are not on the digestive portion 
| of the stomach. They cannot, by their rough- 
ness, assist the trituration or rubbing down of 
the food, for no such office is performed in that 
part of the stomach—the food is softened, not 
rubbed down. They cannot be injurious to the 
horse, for he enjoys the most perfect health when 
the cuticular part of his stomach is filled with 
them, and their presence is not even suspected 
until they appear at the anus. They cannot be 
removed by medicine, because they are not in 
that part of the stomach to which medicine is 
usually conveyed ; and if they were, their mouths 
are too deeply buried in the mucus for any medi- 
cine, that can safely be administered, to affect 
them ; and, last of all, in due course of time they 
detach themselves and come away. Therefore, 
the wise man will leave them to themselves, or 
content himself with picking them off when they 
collect under the tail and annoy the animal.” 
Yet the consequences to the horse, and through 
him to man, might have been very disastrous if 
those protecting laws to which Mr. Youatt refers 
had not been established by the infinitely wise 
Creator of animals and of animal instincts, or 
even if very powerful checks had not been placed 
in constant operation upon the multiplication 
of the insects. “It is fortunate,’ remarks Mr. 
Clark, “ for the animals infested by these insects, 
or rather most beautifully ordained, that their 
numbers are much reduced, and kept within due 
limits, by the hazards they are exposed to in the 
singular round of their propagation.” Some of 
the eggs, in the very act of their deposition, are 
shaken off by the movements of the horse ; some, 
though firmly deposited, are not taken up by the 
horse, or are externally hatched from the action 
of rain or other moisture, and in consequence 
perish; many are destroyed during the horse’s 
process of mastication; many fail to make a 
lodgment in the stomach, but pass on to the in- 
testines; and not a few of the matured larvee are 
BOTS. 
dropped in such situations as to be crushed by 
the horse’s foot, picked up by birds, or unable to 
find a suitable retreat for their transmutation 
into chrysalides. Altogether, one hundred or 
upwards perish in the state of either egg or larva, 
for every individual which attains the perfect 
condition of the fly. 
The red-tailed horse-bot, Gasterophilus hemor- 
rhoidalis, also infests the horse, but in a different 
manner from the great spotted horse-bot, and is 
not. much more than one-half of the size of that 
fly. Its forehead is white; its eyes are brown; its 
thorax is black in the centre, brownish on the 
sides, and thinly pubescent ; its abdomen is 
white at the base, black in the middle, and red- 
dish-yellow at the extremity; its legs are pale ; 
and its wings are unspotted. Its eggs somewhat 
resemble those of the great spotted horse-bot, but 
are so elongated at the apex as to have the ap- 
pearance of standing upon footstalks; and they 
are attached, not to the hairs of the horse, but. 
to his lips. The horse suffers great annoyance 
from the deposition of the eggs, and offers it an 
angry resistance. Whenever a fly approaches 
his lips, he tosses his head, gallops away if he 
can, and dashes his tormentor, if possible, into | 
water ; and, when an egg is deposited upon him, | 
he shows great agitation, rubs his mouth against | 
the ground or upon his forelegs, and frequently © 
makes outward strokes with his forefoot. The 
larvee are smaller, rounder, and proportionally 
longer than those of the great spotted horse-bot ; 
and they attach themselves, in exactly the same 
manner, to the membrane of the stomach; but, 
before making their exit from the intestines, 
they attach themselves for a considerable time 
to the rectum, and there occasion the horse so 
great uneasiness as to make him often kick, and 
sometimes to render his movements awkward.— 
Three other species of gasterophili—designated 
nasalis, salutiferus, and Clarkii—occur in Britain, 
but are so comparatively rare as not to challenge 
description. 
The ox-bot, Gvstrus bovis, is a very annoying 
insect ; and, as its name implies, it usually in- 
fests animals of the ox species. It is about the 
same size as the great spotted horse-bot, or rather 
larger; its forehead is white, and densely hairy ; 
its thorax is yellow in front, black in the middle, 
and ash-coloured behind; its abdomen has an 
apex with tawny-yellow hairs, and a black fascia 
in the middle, and is ash-coloured at the base ; 
its wing-scales are white and very large; and its 
legs are black and tarsi pale. Its eggs are depo- 
sited either on the skin, or in oviposital per- 
foration through it; and its larve grow beneath 
the skin, principally along the sides of the ox’s 
spine, and occasionally on his loins, and cause 
tumours or abscesses analogous to the galls on 
the leaves of willows and other trees, but often 
as large as pigeons’ eggs. When cattle are at- 
tacked by the fly, they frequently become furious, 
bellowing with violence, and running off at their 
