492 1NSECTA. 



perior groove. The upper piece of this sucker, which is inserted 

 near the elbow, is broad, arched and emarginated at its extremity; 

 the three others are linear and pointed, or setaceous; to each of the 

 two lateral ones, representing the maxilla?, is annexed a little mem- 

 branous, narrow palpus, slightly widened and rounded at the end; 

 the inferior seta is analogous to the ligula. The head is hemis- 

 pherical, and mostly occupied by the eyes, that of the males parti- 

 cularly. Its anterior extremity is frequently prolonged in the man- 

 ner of a snout or rostrum, receiving the proboscis underneath when 

 it is doubled. Several species resemble Bombi and other Wasps. 

 This tribe will comprise but the single genus 



SYRPHUS. 



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

 base to point. 



The larva: 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 pre- 

 viously the most slender, then becomes the thickest. 



The sucker of all the remaining Athericera consist of but two 

 setae, the superior representing the labrum, and the inferior the 

 ligula. 



They form three other small tribes which will correspond to the 

 genera CEstrus and Conops of Linnaeus, and to the Musca, Fab. as 

 originally composed. 



We will begin with the tribe of the OUTRIDES consisting of the 

 genus 



CESTRUS, Lin. 



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 antennae are 

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

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

 wings are usually remote; the alulae 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 



