4.58 



FARMERS' REGISTER. 



[No. 8 



to a life of gall and bitterness; though you will 

 now and then find a few hooked on to the duode- 

 num, a httle below the pilorus, or lower orifice of 

 the stomach, that <irow to maturity there in spite 

 of bad food and an impure atmosphere. 



Afier they arrive at the chrysalis state, numbers 

 are lost for one that produces a fly. Dropped on 

 some highway, in some naked pasture, or some 

 pool of water, they are either crushed to death, 

 picked up by birds, who keep a sharp look-out for 

 them, or washed away; or they die for want of the 

 protection of a nidus, indispensable to naked chrys- 

 ales, and especially such as have been nurtured in 

 the high temperature of the stomach ol' a warm 

 blooded animal. The larvas may generally be 

 found adhering in groups to various parts of the 

 inner coat of the stomach of the animal: but the 

 greatest number are generally near its lower ori- 

 fice, where the chyle is purest; their number vary- 

 ing from very few lo (as some have affirmed) ma- 

 ny hundreds. Here they hang in a pendulous 

 manner, and live most probably on the chyle pre- 

 pared by the stomac-h for the nutrltnent of the 

 horse, until they arrive at mature aixe, which gen- 

 erally happens from the middle of May to the first 

 of June; and they are passing from the horse from 

 this time to the first of July, when such as chance 

 lo fall into suilable situations remain for some six 

 or seven weeks in the chrysalis state, and then 

 produce the fly again. 



It has been slated that the larva^ of this insect 

 most probably feed on the chyle in the stomach of 

 the horse. A question, however, arises out of the 

 vulgar opinion on the subject: do they ever prey on 

 the coo^s of the stomach themselves? I confess 

 that I have never had an opportunity of making 

 any satisfactory investigation of the subject; but I 

 incline to think not, because I am satisfied that the 

 larvse of this insect are not armed with any ap- 

 paratus about their mouths, fitting them for ma- 

 king destruction of solid parts. The aperture 

 through whicli they take their food being a simple 

 longitudinal slit, between the two tenlacula or 

 hooks, by which they hold on to the villi of the 

 inner coat of the stomach, brings us to the una- 

 voidable conclusion that they m.ust take their food 

 by the most simple of all processes, and that they 

 cannot take it at all, unless it be in a fluid or pulpy 

 state. The idea, therefore — a very common one, 

 in this part of the country at least — that the bots 

 prey on the solid structure of the stomach itself^ is 

 most probably erroneous. 



Another question then naturally arises: are 

 liorses killed ever by bots or grubs, as they are call- 

 ed? and if so, in what manner are they instru- 

 mental in producing the death of the animal? To 

 doubt that horses are killed by bots would be, with 

 most persons, almost as great a heresy as to disbe- 

 lieve the ordinary doctrines of theolocy. Still, 

 however, I think the fact admits ofa doubt: at any 

 event, I am sure the occurrence is not so fi'equent 

 as it is generally thought to be, and that when it 

 does happen, it is the result of gastric irritation, su- 

 perinduced by the presence of great numbers of 

 these larva?, and not from their laying waste the 

 coats of the stomach by preying on th.em, as is 

 usually believed. The bodies of these larvas seem 

 to be composed of segments of bands, the majori- 

 ty of which are armed with a double row of short, 

 stiff, horny bristle,", of a reddish color, curved back 

 tovvarde the truncated end. The hooks by which 



they are attached to the stomach must of course 

 communicate some irritation; and it is quite possi- 

 ble that the pendulous manner in which they hang 

 from the villi of its inner coat may cause addition- 

 al irritation, by means of the li-iclion that must ne- 

 cessarily take place between these short hooked 

 brisdes and the delicate structure of the inner coat. 

 The irritation, therefore, produced by the presence 

 of a vast number of these larvee may., lor auirht I 

 know, and very probably sometimes does, produce 

 inflammation and mortification of the stomach, 

 and necessarily the death of the animal. But still 

 I am satisfied, that where the numbers are not 

 great, and the horse is healthy in other respects, 

 their presence produces neither mischief nor incon- 

 venience; as the}^ are only occupying a nidus 

 equally natural to them and the animal they inltjst. 



S. of Ghncairn. 



Addenda. — I write this postscript for the purpose 

 of calling the attention of gentlemen to a variety 

 of the oestrus equi, or horse nit-fly, that has not 

 been observed or treated on by any writer that \ 

 know ol! Tliis variety difi'ers in several remarka- 

 ble particulars fi'om that described in the above 

 communication. It is a full size smaller, and dark- 

 er colored than that, and differs materially from it 

 in its habits. The oestrus described is remarkable 

 lor depositing its eggs on no part of the horse that 

 cannot readily be reached and pinched by his 

 mouth. Indeed it seems instinclively to place 

 them on parts most likely to be pinched or licked 

 b\' the animal; and when they are laid elsewhere, 

 it must be considered as an exception to the gen- 

 eral rule, caused perhaps by the urgency of the 

 stimulus of the egg on the parts containmg it, de- 

 manding its mslantaneous depositein the very first, 

 situation that can be commanded. But the small- 

 er fly, now under consideration, deposites its eggs 

 no where, it is believed, but under the throat of 

 the animal, and along the fissure leading from the 

 throat in the direction towards the chin — a part 

 that it is impossible he can get at wi'h his mouth. 



Its manner of making the deposile is also entire- 

 ly difl'erent from that first described. It does not 

 buzz about tiie horse as the other does, nor does it 

 poise itself in the air for a moment, in the vicinity 

 of the part on which it intends to attach its egg: 

 hut rising suddenly, either from the ground or from 

 something on which it has alighted, it darts with 

 great boldness and rapidity at the horse's throat, 

 or the parts between that and the chin, causing 

 him at first to throw up his head suddenly and 

 shake it, and then to drop his ears in a semi-pendu- 

 lous posture^ and to hold his head remarkably still, 

 as if listening for another attack of the fly; on the 

 repetition ol which he throws up his head still 

 more violently, often raising his fore feet from the 

 earth and bringing them near his chin, as if to 

 frighten away the insect. 



This variety of the oestrus is much more keen- 

 ly and actively formed, and its movements are 

 more rapid than those ol that lately described. 

 Still, however, if the rider will stop his horse, and 

 practise a little patience when he perceives him at- 

 tacked by one of tliese insects, he ma3\ by watch- 

 ing acutely, discover the flv, and most probaby its 

 retreat between the times of its attacks: for as soon 

 as it has deposited an egg, it alights on some con- 

 venient oljject, or the ground, most probably to pre- 

 pare another ior deposile, when the attack is re- 

 pealed, causuig the horse again to act, not very 



