350 INSECTA, 



the pupa. It becomes shortened, assumes an ovoidal or globular 

 figure, and the anterior portion, which in the larva was the narrowest, 

 increases in diameter, or is sometimes even thicker than the opposite 

 extremity. Traces of the annuli, and frequently vestiges of the 

 stigmata are observed on it, although the latter no longer serve for 

 respiration. The body is gradually detached from the skin or cocoon, 

 assumes the figure of an elongated and extremely soft ball, on Avhich 

 none of its parts are perceptible, and soon passes into the state of a 

 pupa. The Insect issues from its shell, by removing with its head 

 the anterior extremity, which flies off like a cap, that part of the 

 cocoon being so disposed as to facilitate this result. 



But few of the Athericera are carnivorous in their perfect state. 



They are generally found on trees, leaves, and flowers, and some- 

 times on the faeces of animals. 



This family comprises the genera Conops and (Estrus of Linnaeus, 

 and most of his genus Musca. 



We must naturally separate from the last those numerous species 

 in which the sucker is composed of four pieces, and not of two, as 

 in all the other Athericera. They will form our first tribe, that of 

 the Syrphid^. 



Their proboscis is always long, membranous, geniculate near the 

 base, terminated by two large lips, and encloses the sucker in a su- 

 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 maxillae, 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 hemispherical, 

 and mostly occupied by the eyes, that of the males particularly. Its 

 anterior extremity is frequently prolonged in the manner of a snout 

 or rostrum, receiving the proboscis underneath when it is doubled. 

 Several species resemble Bombi and other Wasps. M. Lepeletier de 

 Saint- Fargeau has communicated to the Academic Royale des Sci- 

 ences, come curious observations on the unnatural coition of some of 

 these Insects, or to use his own words, on their " marriages adulte- 

 rins," the result of which, however, he was unable to follow. 



This tribe will comprise but the single genus 



S\RPHUS. 



A first general division will consist of all those species in which 

 the proboscis is shorter than the head and thorax. The snout, in 

 those where it is distinct, is perpendicular and short. 



