Mr. Clark' j Objhvatlons on the Genus Oe/l/us. 29 r 



pll the fpecies in one view in their various Hates, taken from the 

 fubjects themfelves; and this will be the more ufeful and necef- 

 fary, as hardly any of the larvce, or perfect infects, have ever ye! 

 been intelligibly figured. 



The obfcure and lingular habitations of the Bi itiili Oeflri are the 

 ftomach and interlines of the horfe, the frontal and maxillary 

 ■finufes of the lheep, and beneath the (kin of the backs of horned 

 cattle. In other parts of the world they inhabit various other 

 animals ; but our prefent enquiry is neceilarily limited to thole of 

 our own country, which includes all thofe about which any dif- 

 ficulty or obfcurity has arifen. 



Of the Oestrus Bovis. 



This rare fpecies has been entirely omitted by Linnxus, and 

 appears to have been unknown to nearly all the later writers on 

 Natural Hiftory, who, inftead of the true CE. Bovis, have defcribcd 

 a fpecies peculiar to the horle under that name. Linnaeus imagined 

 alfo that it was the fame fpecies which inhabited both the ftomachs 

 of horfes and the backs of oxen*, which certainly never happens. 



The larva, tab. 23, fig. I, taken from the back of the cow, is fo 

 unlike the other larvae of this genus, that I did not imagine, till I 

 procured the fly from it, that it was the larva of an Ocjlrus. It 

 does not pofTefs the aculei, the marginal fiUe % or the lips, which arc 

 the prominent characters of the larvae of the CE. Equi and hamor- 

 rhoidalis. 



It lives beneath the ikin, being fttuated between it and the cel- 

 lular membrane, in a proper fack or abfeefs, which is rather larger 

 than the infect, and by narrowing upwards opens externally to the 

 air by a fmall aperture. 



* Habitat in ventriculo equorum, in boum doifo. Linn, Syft, Nat. 2. p. 969. ed. du<id<:c;m>s. 



P p 2 When 



