458 JNSECTA. 



SYRPHUS. 



In Syrphus, properly so called, the abdomen is gradually narrowed from base 

 to point 



The larvae feed exclusively on aphides of all kinds, frequently holding them 

 in the air, and soon exhausting them by suction. Their body forms a sort of 

 elongated cone, and is very uneven, or even spinous. When about to become 

 pupae, they fix themselves to leaves, &c., with a kind of glue. The body is 

 shortened, and its anterior portion, which was previously the most slender, then 

 becomes the thickest. 



The sucker of all the remaining Athericera consist of but two setse, the 

 superior representing the labrum, and the inferior the ligula. 



They form three other small tribes which will correspond to the genera 

 (Estrtts and Conops of Linnaeus, and to the Musca, Fab., as originally 

 composed. 



We will begin with the tribe of the CESTRIDES consisting of the genus 



CEsTRUS, Limit, us. 



Which is very distinct, as in place of the mouth we find but three tubercles, or 

 slight rudiments of the proboscis and palpi. 



These insects resemble large and densely pilose flies, and their hairs are 

 frequently coloured in bands like those of the Bombi. Their antenna? are 

 very short ; each is inserted in a fossula over the front, and terminated by a 

 rounded palette with a simple sefa on the back near its origin. Their wings 

 are usually remote ; the alula? are large and conceal the halteres. The tarsi are 

 terminated by two hooks and two pellets. 



These insects are rarely found in their perfect state, the time of their 

 appearance and the localities they inhabit being very limited. As they deposit 

 their eggs on the body of various herbivorous quadrupeds, it is in woods and 

 pastures that we must look for them. Each species of (Estrus is usually a 

 parasite of one particular species of mammiferous animal, and selects for the 

 location of its eggs the only part of its body that is suitable for its larva?, 

 whether they are to remain there, or pass from thence to the spot suited for 

 their development. The ox, horse, ass, rein-deer, stag, antelope, camel, sheep 

 and hare, are the only quadrupeds yet known, which are subject to be inhabited 

 by the larvae of the (Estri. They seem to have an extraordinary dread of the 

 insect when it is buzzing about them for the purpose of depositing its eggs. 



The domicile of the larvae is of three kinds ; we may distinguish them by 

 the names of cutaneous, cervical, and gastric, as some live in the lumps or 

 tumours formed on the skin, others in some part of the interior of the head, 

 and the rest in the stomach of the animal destined to support them. 



(E. bovii, De Geer. From six to seven lines in length, and densely pilose ; 

 thorax yellow, with a black band ; abdomen white at base, with a fulvous 

 extremity ; wings somewhat obscure. 



