298 Mr. ClARk'j Obfervations on the Genus Oe/lrus, 



Of the Oestrus Equ'i. 



The larva of this fly is that which is very commonly found in 

 the ftomach of horfes, and is reprefented in fig. 7. 



Thefe larvce attach themfclves to eveiy part of the ftomach, but 

 are generally moft numerous about the pylorus ; and are fometimes, 

 though much lefs frequently, found in the inteftines. 



Their numbers in the ftomach are very various, often not more 

 than half a dozen, at other times more than a hundred, and, if fome 

 accounts might be relied on, even a much greater number than this. 

 They hang moft commonly in clufters, being fixed by the fmall 

 end to the inner membrane of the ftomach, which they adhere to 

 by means of two fmall hooks, or tentacula. Of theie a reprefen- 

 tation confiderably enlarged is feen in fig. 22. 



When they are removed from the flomach they will attach them- 

 felves to any loofe membrane, and even to the Ikin of the hand. 

 ]"or this purpofe they fheath or draw back the hooks almoft en- 

 tirely within the ikin, till the two points come clofe to each other; 

 they then preferit them to the membrane ; and keeping them pa- 

 rallel till it is pierced through, they expand them in a lateral 

 direflion, and afterwards, by bringing the points downwards to- 

 wards themfelves, they include a fufficient piece of the membrane, 

 and remain firmly fixed for any length of time, without requiring 

 any farther exertion. 



Thefe hooks, the better to adapt them to this purpofe, appear 

 to have a joint near their bafe. The larva of CE. hamorrhoi- 

 dalis and ovis, and probably all thofe which feed on the mucous 

 membranes lining the internal caaals of the body, are alfo fur- 

 niihed with thefe tentacula ; whilft thofe larva which inhabit be- 

 neath 



