Air. Clark* j Obfervations on the Genus Oejlrus* 315 



fig. 16 and 17. The manner in which this fpecies depofits its ova 

 has, I believe, not been defcribed ; nor is it eafy to ice, though 

 clofe to the animal at the time, exactly in what way this is accom- 

 plifhed, owing to the obfcure colour and rapid motion of the 

 fly, and the extreme agitation of the iheep ; but the motions of 

 the fheep afterwards, and the mode of defence it takes to avoid it, 

 can leave but little doubt that the egg is depofited on the inner 

 margin of the noftril. 



The moment the fly touches this part of the fheep, they (hake 

 their heads, and ftrike the ground violently with their fore-feet; at 

 the fame time holding their nofes clofe to the earth they run away, 

 looking about them, on every fide, to fee if the fly purfues : they 

 alfo lmell to the grafs as they go, left one fhould be lying in wait 

 for them. If they obferve one, they gallop back, or take fomc other 

 direction. As they cannot, like the horfes, take refuge in the water, 

 they have reconrfe to a rut, or dry dully road, or gravel pits, where 

 they crowd together during the heat of the day, with their nofes 

 held clofe to the ground, which renders it difficult for the fly con- 

 veniently to get at the noftril. 



Obfervations on thefe flies are bell: made in warm weather, and 

 during the heat of the day, when, by driving the fheep from their 

 retreats to the grafs, the attack of the fly and the emotions of the 

 fheep are eafily obferved. 



I imagine the noftril, from repeated attacks, and the confequent 

 rubbing againft the ground, becomes highly inflamed and fore, 

 which occaftons their touch to be fo much dreaded by the iheep. 



From the difficult arid very precarious mode this fpecies and the 

 hamorrhoidalis purfue in depofiting their eggs, they cannot fuc- 

 cefsfully depofit more than half of them. 



* 



Ss 2. General 



