8U ANNUAL REGISTER, 1805. 



out from their respective cells, and 

 falling to the ground, each creeps 

 beneath the first convenient shelter, 

 and lying in an inert state, becomes 

 contracted into an oval form, but 

 without casting the larva skin, which 

 dries and hardens round it. VViien 

 the included insect is ready for ex- 

 clusion, it forces open the top of 

 the pupa or chrysalis coat, and 

 emerges in its perfect form, having 

 remained within the chrysalis some- 

 what more than a month. 



Though the history of this insect 

 in its larva state has long ago been 

 detailed with sufficient accuracy by 

 Vallisneri, Reaumur.and others, yet 

 the Hy itself appears to have been 

 yt'vy generally confounded, and (hat 

 even by Linnieus himself, with a 

 very 'different species, resembling it 

 in size, but which is bred in the sfo- 

 niach and intestines of horses, the 

 larva; being no other than the whit- 

 ish, rough maggots which farriers 

 call by the title of bots. This insect 

 is tlie oC'fnts equi, extremely well 

 described by INIr. Bracy Clark in the 

 third volume of the transactions of 

 the Linna'an society. It is a trifle 



smaller than the oestrus buiis^ and is ' 

 of a yellowish-brown colour, with a 

 dusky band across (he thorax, and 

 the tip of the al)dojnen of similar co- 

 lour : tlie wings arc whitish, wi(h a 

 pale-dusky bar across the middle of 

 cacJij and two dusky spots at the 



The manner in v Inch (he young 

 larva" or bots arc introduced into the 

 stoma'^ii and bowels of the animal 

 tliey iiilest, is singularly curious, and 

 cannot be better delivered than in 

 the words of the ingonious ob- 

 server. 



" A\ hen the female has been im- 

 " pregnatcd, and the eggs are sulh- 

 " ciently matured, she seeks among 



" the horses a subject for her pur- 

 " pose, and approaching it on the 

 " wing, she holds her body nearly 

 " upright in the air, and her tail, 

 " which is lengthened for the pur- 

 " pose, curvedinwardsand upwards: 

 " in this way she approaches the 

 " part where she designs to deposit 

 " her egg ; and suspending herself 

 " for a lew seconds before it, sud- 

 " dcidy darts upon it, and leaves 

 " her egg adhering to the hair: she 

 " hardly appears to settle, butmerc- 

 " ly touches the hair with the egg 

 " held out on the projected point 

 " of the abdomen. The egg is made 

 " to adhere by means of a glutinous 

 " liquor secreted with it. She then 

 " leaves the horse at a small dis- 

 " tance, and prepares a second egg> 

 " and, poising herself before the 

 " part, deposits it in the same way. 

 " The liquor dries, and the egg be- 

 " comes (irmly glued to the hair: 

 " this is repeated by various flics, till 

 " four or live hundred eggs* are 

 " sometimes placed on one horse. 

 " The horses, when they beCome 

 " used to this fly, and find that it 

 " does them uo injury, as the taba- 

 ' ni and conopes, by sucking their 

 " blood, hardly regard it, and do 

 " not appear at all aware of its in- 

 " sidious object;. The skin of the 

 " horse is ahvays thrown into a tre- 

 '* mulous motion on the touch of 

 " this insect, which merely arises 

 " from the very great irritability of 

 " the skin and cutaneous muscles 



" at this season of (he yearf, occa- 

 " sioned by the continual teasing 

 " of the Hies, till at length these 

 " muscles act involuntarily on the 

 " slightest touch of any body what- 

 " ever. The inside of the knee is 

 " the part on which these flies are 

 " most fond of depositing their eggs, 

 " and next to this, on the side and 



" back 



Horses sometimes ;ippear to be nearly covered by tliera. f August & Septemb. 



i 



