DIPTERA. 491 



never exhibits annular divisions. The palpi, when at rest, are con- 

 cealed. 



FAMILY V. 



ATHERICERA. 



Here the proboscis is usually terminated by two large lips. The 

 sucker is never composed of more than four pieces, and frequently 

 presents but two. 



The larvae have a very soft, extremely contractile, annulated body, 

 narrowest and most pointed anteriorly. The head varies as to 

 figure, and its external organs consist of one or two hooks, accom- 

 panied in some genera by mammilla, and probably in all by a sort 

 of tongue destined to receive the nutritious juices on which they 

 feed. They usually have four stigmata, two situated on the first 

 ring, one on each side, and the two others on as many circular, 

 squamous plates, at the posterior extremity of the body. It has 

 been observed that these latter, at least in several, were formed of 

 three smaller and closely approximated stigmata. The larva has 

 the faculty of enveloping these parts with the marginal skin, which 

 forms a sort of purse. They never change their skin. That which 

 invests them when first hatched becomes indurated, and thus forms 

 a sort of cocoon for 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 de- 

 tached from the skin or cocoon, assumes the figure of an elongated 

 and extremely soft ball, on which 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 facili- 

 tate this result. 



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



They are generally found on trees, leaves and flowers. 



Their proboscis is always long, membranous, geniculate near the 

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



