BOTS. 
utmost speed, with extended tail and outstretched 
neck ; and if attacked when yoked to the plough, 
they instantly become so unmanageable that 
many ploughs used to be provided with a con- 
trivance for giving them immediate liberation. 
A herd of cattle when almost driven home have 
been struck with such terror by meeting an ox- 
bot, that they instantly wheeled about, ran off 
in a brisk retreat, and defied the shouts, sticks, 
and stones of their drivers, till they found pro- 
tection in a pond of water; and frequently a 
team of oxen, when attacked at their work in 
| the field by a bot, and not instantly liberated by 
means of the contrivance to which we have re- 
ferred, have fled with the plough at their heels, 
totally regardless of both their driver and the 
enormous encumbrance upon their flight. The 
larva of the ox-bot has an oblong-oval shape ; it 
consists of eleven segments formed by transverse 
bands, which are crossed at the sides by longi- 
tudinal lines; and it has, on each side of every 
segment, a distinct spiracle or breathing-hole. 
A cyst or minute cell within the substance of 
the skin is the abode of the young larva, and 
the commencement of the abscess or tumour; 
this gradually enlarges with the growth of the 
_ larva; a secretion of pus, occasioned by the local 
| irritation, supplies the insect with food; and a 
| minute opening on the crown of the tumour, 
permits the insect to place the extremity of its 
principal air-tube in contact with the atmo- 
sphere, and afterwards, at the season of maturity, 
to withdraw its whole body from the tumour, 
A curious and very beautiful instinct incites 
| every larva, when about to become a chrysalis, 
|| to withdraw from its nidus, neither during the 
night when it would perish before it could get a 
place of refuge, nor during the heat of the day 
_ when it would be destroyed by the intensity of 
the sun’s rays, but exactly at the time of the 
morning when temperature and other circum- 
stances are most suitable to its condition. In 
its earlier stages of existence, the larva is white 
like that of most other flies; in the later stages, 
| it darkens in colour till it becomes almost black ; 
| and, on its passing into the pupa-state, it js trans- 
muted into so rigid a chrysalis, that the fly, when 
perfected, escapes from it only through a won- 
derful contrivance in its formation, resembling, 
in microscopic miniature, the lid of a snuff-box. 
The tumours occasioned in the skin of cattle 
[Se Ee 
by the ox-bot have long been popularly regarded 
as a disease under the name of warbles, wormals, 
or womils ; and in the years 1823 and 1824, they 
were so exceedingly numerous and virulent 
upon the cattle of the department of Loiret in 
France, as to occasion fever, inflammation, and 
death. Except in rare instances, however, war- 
bles do not affect the healthy condition of cattle, 
but, on the contrary, are regarded by butchers 
as indications of soundness and strength. Yet 
hides which have been affected with warbles are 
irretrievably damaged, and are readily and greatly 
BOTTOM HEAT. 
depreciated by the tanner; the tortures, too, 
which cattle suffer at the deposition of the eggs, 
are injurious to their welfare, and sometimes oc- 
casion considerable accidents ; and, for these rea- 
sons, efforts ought to be made, in every district, 
to exterminate or at least keep down the bot. 
Either the insertion of a red-hot needle, or the 
application of a little corrosive liquor, or squeez- 
ing out and crushing with the finger and thumb, 
will kill the larve; and if all the farmers of a 
district would examine their cattle and destroy 
the larvee, warbles would speedily become very 
rare. Yet Linnzeus, Bracy Clark, and other 
eminent naturalists, contend—on principles which 
certainly harmonize well with the general laws 
of utility and beneficence which govern all the 
works of the all-wise Creator—that all kinds of 
bots, instead of being on the whole pernicious, 
are positively beneficial to the general health of 
the animals which they infest. 
The sheep-bot, Gistrus ovis, is the only other 
species which we require to notice. Its length 
is scarcely five lines ; its forehead has a dusky-red 
colour, with a blackish depression; its antennee 
are black ; its thorax is ash-grey, with numerous 
small, black, hairy warts; its abdomen is a vari- 
egated silky-white and light-yellow; its legs are | 
pale red; its wings are clear and unspotted; and 
its wing-scales are white and large. The eggs 
are supposed to be deposited on the margin of 
the nostrils of the sheep; and the deposition of 
them appears either to inflict or to occasion 
much pain,—and at all events is greatly dreaded 
by sheep, and attempted to be warded off by va- 
rious methods of defence. Sheep, when attacked, 
in dry hot weather, run into public roads, lie 
down upon the dusty ruts, and hold their heads 
close to the ground; or they continue to stand, 
and place their nose between their fore-legs al- 
most in contact with the ground; or, in an open 
field, they rush together into a dense assemblage, 
and so push their noses together or hold them to 
the ground, that only those on the outskirts of | 
the flock remain accessible to the fly. The larvae 
are soon hatched by the heat and moisture of the 
nostrils; they speedily effect a lodgment in the 
frontal maxillary and in other cavities of the 
face; they feed upon the pus which their irritat- 
ing presence occasions to be secreted ; and when 
they become full-grown, they drop through the 
nostrils, and seek an asylum of transformation 
into a pupa state, beneath some loose soil or in 
adhesion to a blade of grass—Clark’s Hssay on 
Bots.—Westwood’s Entomology—Papers of Mr. 
Duncan in Quarterly Journal of Agriculture — 
Youait on the Horse.—Cattle, in Inbrary of Usefut 
Knowledge —Bartle’s Farriery— White's Veteri- 
nary. 
BOTTOM HEAT. The heat maintained in 
brick pits by the fermentation of tanner’s bark, 
oak-leaves, stable-litter, or other vegetable mat- 
ter. It maintains a temperature of from 60° to 
90°, and has long been used by gardeners for 
