B O T 



in the abfccfs at pleafure, and to crawl out of it when ripe, 

 and renders the ul'c of the teiitaculz, obfervable at the fmall 

 end in the other fpccies, not ncccflary- in this. 



" Tliefe hooks, being ercftcd by the mufclei of the (liin, 

 according to the feries of them ufcd by the larva, it appears 

 to be raifcd or dcprelTed in the abfcifs ; and by tliis motion, 

 and the confequent irritation, a more or lefs copious fecre- 

 lion ot pus is produced for the fullcnance of the lar\'a. The 

 chrxfJules continued in tliat Hate from about the latter end 

 of June till about the middle of Auguil, when llie fly, forc- 

 ing; open a vcr\- fingular marijinated triangular hd, or opci- 

 (uhim, at the ("mall end, made its appearance. 



•' Although its tffetts on the cattle arc fo often remarked, 

 yet the fly itfclf is rarely feen or taken, as the attempt would 

 be attended with con fiderable danger, if ui purfuit of the oxen. 

 The pain it inflifts in depofiting its eggs, apjxrars to be very 

 fcvcre. When one of the cattle is attacked by this fly, it is 

 caCly known by the extreme terror and agitation of the 

 whole herd. The unfortunate ol)jc£l of the attack runs bel- 

 lowing from among them to fomc diftaiit part of the heath, 

 or the neartll water. The tail, from the feverity of the pain, 

 is held with a tremulous motion lli-aight from the body ; and 

 the head and neck flretched out to the utmoft. The reft, 

 from fear, generally follow to the water, or difperfe to dif- 

 ferent parts of the ticld. 



" When tlie oxen are yoked to the plough, the attack of 

 this fly is attended with real danger to tlie drivers ; fince 

 they become pcrfeftly uncontrolablc, and will often run with 

 the plough dirc£\ly forwards through the hedges, or what- 

 ever obllruds their way. 



" There is provided, on this account, to many ploughs a 

 contrivance immediately to fet them at liberty. The fingu- 

 lar fctne attending the attack of this fly on the herd, has 

 often been the fubjecl of poetical defcription ; no one has, 

 however, more naturally or elegantly delineated it than the 

 bard of Mantua : 



" Eft lucos filari circa ilicibufque virentem 



Plurimus alburnum volitans cui nomen afilo 

 Romanum eft, oeftron Graii vertere yocantes : 

 Afper, acerba, fonans : quo tota extcrrita fylvis 

 DifTugiunt armenta ; furit mugitibus aether 

 Concuftus, fylvofque, et ficci ripa Tanagri." 



Gcorg. lib. iii. ver. 146 — liji. 



" The ftrongcft and heakhiell bcafts feem conftantly to 

 be preferred by this fly ; and their poircfting them in their 

 backs is confidered as a criterion of goodnefs with the dealers 

 in cattle ; and the tanners obferve, that their beft andftrong- 

 ell hides have the greattft number of bot-holes in them. 



" The whole of this family of infe.fts appear to have a 

 ftrong diOike to moifture; fince the animals find a fecure re- 

 fuge, when they get into a pond or brook, where the other 

 flies which annoy them, follow without hefitat-oii, but the 

 oeftri rarely or never ; and during very cold, rainy, or 

 V indy weather, they are not to be feen. 



" Among the country-people, the larvae of this infeft are 

 commonly known by the name of warbles, wornuls, or 

 wormuls, or more properly bots." 



We now tranfcribe from the above memoir what is moft 

 worthy of notice rcfpefting the oefirus eqtii, or large horfe- 

 bot. 



" Thefe Iarv2 attach themfelves to every part of the fto- 

 mach, but are in general moft numerous about the pylorus, 

 and are fometimes, though much lefs frequently, found in 

 the inteftines. They hang moft commonly in clufters ; being 

 fixed by the fmall end to the inner membrane of the fto- 

 mach, where they adhere by means of two fmall hooks or tenta- 

 cula- When removed from the ftomaeh, they will attach them- 



B O T 



felves to any loofe membrane, and even to the fliin of th< 

 hand ; for this purpofe, they draw back their hooks almoft 

 entirely within the fl<in, till the two points of thefe hooks 

 come clofc to each other ; they then prefent them to the 

 membrane, and keeping them parallel till it is pierced 

 through, thcv expand them in a lateral direftion ; and af- 

 terwards, bv bringing the points downwards, or towards 

 themfelves, they include a fufficicnt piece of the membrane 

 with each hook, and thus remain firmly fixed, for any length 

 of time, without any tarther exertion from the animal. 



" All thofe bots which feed on the mucous membranes 

 lining the canals of the body, are provided with thefe tenta- 

 cula ; whilft thofe which inhabit beneath the Ikin, will 

 be found univerfally without them. The oeftrus of the 

 ftieep has them alfo, but ufes them only in paffing over 

 the membranes on which it lives, making them a fixed 

 point to which it draws up its body, and thus fecures its 

 pafTage along thofe fmooth and lubricated furfaces of the 

 uoftrils. 



" The larva of this bot, when very young, is of a cylindri- 

 cal figure, of a pellucid ruby red, and appears without fpincs 

 to the fe'gments. As it acquires an increafe of fize, it af- 

 fumes a more flattened appeara"ce, becomes whiter ; and the 

 fpincs, which are tipt with black, become very vifible, being 

 placed in double lines, and ' -• directed towards the tail, or 

 truncated end of the larva. 



" Their food is probably the ciivle, which, being nearly 

 pure aliment, may go almoft wholly to ih-,- compofition of 

 their bodies without any excrementitiou-. refiduc; tnough» 

 on diffeftion, the inteftine is found to contain a yellow or 

 greenifli matter, which is derived from the colour of the 

 food, and ftiews that the chyle, as they receive it, is not 

 perfeftly pure. ' 



" The fiownefs of their growth, and the purity of their 

 food, muft occafion what they receive in a given time to be 

 proportionably fmall ; from whence probably arifes the extreme 

 dif&culty there is found in deftroying them by any medicine or 

 poifon thrown into the ftomaeh. Opium, tobacco, or the 

 draftic purgatives, which often bring away in abundance 

 the common worms of the inteftines, produce little or na 

 effedl on thefe. 



" On openinfT the body of the bot, and removing the ge- 

 latinous matter, the air tubes are feen, and feem of a fplendid 

 filvery celour, glittering veiy beautifully, as though they 

 were injefted with the pureft mercury ; they remain diftended 

 by their own inherent elafticity, and are filled with air to their 

 minuteft ramifications. 



" Refpiration appears to be the office of thefe air-canals, 

 which are the lungs of the larva ; and, confidered in this 

 point of view, they arc much larger than the refpiratory 

 organs of any other animal, which is the more extraordrr.ary, 

 if the refpiration of animals be for the produttion of animal 

 heat ; this being unneceffary to larvae, that are fupplied fa- 

 abundantly with it from the high temperature of their refi- 

 dence in the living ftomaeh. Nor can thefe organs be formed 

 for the purpofts of the future infefl, fince they cannot be 

 dete(Jtcd in either the chryfalis or fly. One ftiould almoft, 

 from this circumftance, be led to fufpect that the refpiration of 

 animals was more intimately connecled with the reception of 

 food, and the converting it into living matter than any other 

 defign. Though it would alfo appear, that the impurity of the 

 air in the ftomaeh, and its cafual fupply might render thefe 

 larger refervoirs neeeffary. 



" The larvie of the large horfe-bot attain their full 

 growth about the latter end of May, and are coming from, 

 the horfe from this time to the latter end of June, or fome- 

 times later. On dropping to the ground, they find out 



fbme 



