314 ^ r - Clark'j Obfervations on the Genus Oeftrus.. 



prominent ring or margin, which ferves the fame purpofe in an in- 

 ferior degree as the lips of the CE. Equi and hcemorrboidalis, by occa- 

 fionally clofing over, and cleaning the horny plate. When this 

 margin opens after clofing over the plate, it occafions frequently a 

 flight fnap from the fudden admiffion of the air* 



When young thefe larva are perfectly white and tranfparent, 

 except the two horny plates, which are black. As they increafe irt. 

 fize the upper fide becomes marked with two tranfverfe brown lines. 

 on each fegment, and feme fpots are feen on the fides. 



They move with confiderable quicknefs, holding with the ienta- 

 cula as a fixed point, and drawing up the body towards them. On 

 the under fide of the larva is placed a broad line of dots, which, on. 

 examination with glafTes, appear to be rough points,, ferving per- 

 haps the double purpofe of affifting their paffage over the fmooth 

 and lubricated furfaces of thefe membranes,, and of exciting alfo a 

 degree of inflammation in them where they reft, fo as to caufe a 

 fecretion of lymph or pus for their food, 



I have madly found thefe animals in the horns and frontal finufes, 

 though I have remarked that the membranes lining thefe cavities 

 were hardly at all inflamed, while thofe of the maxillary finufes were 

 highly fo. From this I am led to fufpect they inhabit the maxillary 

 finufes, and crawl, on the death of the animal, into thefe fituations 

 in the horns and frontal finufes. 



The breeds of thefe, like the CE. Bovis, do not appear confined to 

 any particular feafon ; for quite young and full-grown larva may be 

 found in the finufes at the fame time. 



When full-grown they fall through the noftrils, and change to the 

 pupa ftate, lying on the earth, or adhering by. the fide to a blade of 

 grafs. See fig. 15. 



The fly burfts the fhell of the pupa in. about two months. See 



fig. 



