Mr. Clark'* Obferuations on the Genus Oejlrus. 309 



ever appear to chnnge their fkin. If they did, it is probable they 

 would lofe their hold, as the hooks are principally connected with 

 the ikin, and ieparate with it by maceration, leaving only an in- 

 dentation where they were lodged. 



Thefe larva', being forcibly lqueezed, contract themfelves into a 

 fmaller lpace, and become very hard. If is probable they in this 

 way refill the violent preffure they mud occafionally fuftain, from 

 the weight of the food and the actions of the ftomacb, and in 

 paQmg through the interlines and th.tfphi?i£ler am. 



After remaining in the chryjalh ftate about two months, the fly 

 appears. See fig. 12 and 13, — the male and female, — and their de- 

 fcription in the fequel of the paper. 



This fpecies may Hill retain the name of hemorrhoidal, without 

 any impropriety, not from the fuppofed hiftory of its entering the 

 anus, but from the termination of the abdomen being red, Linnaeus 

 having generally chofen to diftinguifh the infe&s fo marked by 

 that name; alfo from their refembling the hemorrhoids or piles, while 

 hanging to the extremity of the reSium *. 



It feems hitherto to have been generally believed among natu- 

 ralifts, that the female fly enters the anus of the horfe in a very ex- 

 traordinary manner, to depofit its eggs f. 



* The idea entertained by the Romans o£ this appearance is truly lingular : Hujnf- 

 niodi pafllonis lignum eft (morbus coriaginofus) cum invenitur humor in ano fabae coctae 

 fimilis : eft namque fanies ex illis vulneribus quae beftiolae intrinfecus fecerunt. Flavius 

 Vegetius de Arte Veterhiaria, ed. Manheim. p. 63. 



■f Reaumur, torn. iv. p. 543, relates this circumftance on the authority of Dr. Gafpari. 

 From the account of its getting beneath the tail, I mould fufpecl: the fly he faw was the 

 H'ippobofca equina, which frequently does this. Its getting within the reclum appears to 

 have been additional. That a fly might depofit its eggs on the verge of the anus is not 

 impoflible, though we know no inftance of it. 



The 



