Mr. ClarkV Ol'fervalions on the Genus Oe/lrus. 309 



ever appear to change their ikiii. If they did, it is probable they 

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

 the Ikin, and feparate with it by maceration, leaving only an in- 

 dentation where they were lodged. 



Thefe larvcc, being forcibly fqueezed, contradl themfelves into a 

 fmaller fpacc, and become very hard. It is probable they in tliis 

 way refift the violent prcilure they muft occafionaliy fuftain, from 

 the weight of the food and the adlions of the ftomach, and in 

 paffing through the intcftines and t\\cfphl?igler an/. 



After remaining in the chryfalis 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 ftill retain the name of hiemorrhoidalis, without 

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

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

 having generally chofen to diftinguilli the infects fo marked by 

 that name; alfo from their refembling the hemorrhoids ov piles,wh.i\& 

 hanging to the extremity of the reSlum *. 



It leems 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 of this appearance is truly Angular: Hujuf- 

 modi paffionis fignum eft (morbus coriaginofus) cum invenitur humor in ano fabx coftse 

 fimilis : eft namque fanies ex illij vulneribus quse beftiolae intrinfccus fecerunt. Flavins 

 Vegettus de Arte Veterinaria, 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 fliould fufpedl the fly he faw was the 

 Hippobofca eqiiimi, which frequently does this. Its getting within the recium appears to 

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

 impofEble, though we know no inftance of it. 



The 



