118 BOTS IN ANIMALS. 



of the sheep; but the motions of the slieep afterwards, and the mode 

 of defence it employs to avoid it, can leave but little doubt that the egg 

 is deposited on the inner margin of the nostril. 



The moment the fly touclies this part of the sheep, they shake their 

 heads, and strike the ground violently with the fore feet : at the same 

 time holding their noses to the earth, they run away, looking about 

 them, on every side, to see if the fly pursues ; they also smell the grass 

 as they go, lest one should be lying in wait for them. If they observe 

 one they gallop back, or take some other direction. As they cannot, 

 like oxen or horses, take refuge in the water, they have recourse to a 

 rut, or dry dusty road, or gravel pit, where they crowd together during 

 the day, with their noses held close to the ground, which renders it dif- 

 ficult for the fly conveniently to get at the nostril. 



Sheep are particularly subject to disorders attended with vertigo, 

 probably arising from an affection of the brain, and it is a common no- 

 tion that this is occasioned by worms in the brain, when the real fact 

 is, that these worms, instead of occasioning this disease, tend to divert 

 its attacks, or, at least, to render them less fatal. 



I shall defer some remarks on other species of Oestrus^ especially 

 that which inhabits the stomach of the horse, for your next No. of the 

 Journal, and shall conclude this paper with descriptions of the two in- 

 sects spoken of above : 



Oestrus Bovis. — Wings fuscous, immaculate — abdomen with a black me- 

 dial band ; end of the abdomen covered with fulvous hairs. 

 Front white, tomentose. Thorax yellowish before — black in the 

 middle- — with four longitudinal naked lines — cinereous behind. 

 Feet black — tarsi pale. 



Abdomen of the female with a black attenuated style — evolving 

 by compressing- 



Larva subcutaneous, apodal, fuscous — with eleven segments — 

 lines transverse, scabrous, interrupted. 

 O. Ovis. — Wings pellucid — abdomen versi-colored with black and white. 

 A few scattering hairs on the. body — vertex of the head with ex- 

 cavated points. Thorax cinereous with black elevated points — 

 setigerous — 'with four black lines — ahdomen whitish-cinereous 

 spotted with black. 



Larva white — ovate — hcfore, acuminate with two hooks — be- 

 hind, truncate with a prominent margin and two black respira- 

 tory scales. — Move, convex with black lines and points. Below, 

 plain, in the middle of the segments marked with minute rough 

 black lines. RusTicus. 



