DIPTERA. ; 275 
FAMILY V. 
ATHERICERA. 
Where 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 larve 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, 
accompanied in some genera by mammillx, 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 
onas 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 approx- 
imated 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 some- 
times even thicker than the opposite extremity. Traces of 
the annuli, and frequently vestiges of the stigmata are ob- 
served on it, although the latter no longer serve for respi- 
ration. The body is gradually detached 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 dis- 
posed as to facilitate this result. 
