298 Mr. Clark*; Ohfcrvatlom on the Genus Oejirtts. 



Of the Oestrus Equl. 



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

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



Thefe larva; attach themfelves to every part of the ftomach, but 

 are generally moil numerous about the pylorus - and are fometimes, 

 though much lefs frequently, found in the interlines. 



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 mod commonly in duffers, 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 thefe a reprefen- 

 tation considerably enlarged is feen in fig. 22. 



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

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

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

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

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

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

 direction, 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. bamorrh&i- 

 dalls and avis, and probably all thofe which feed on the mucous 

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

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

 neath 



