20 © THE NORTH AMERICAN SPECIES OF DROSOPHILA. 
I have not examined the two younger stages, nor studied the transi- 
tions between them, beyond observation that the cephalopharyngeal 
skeletons are cast off and may be seen in the food. The following 
notes all apply to third-stage larve. 
The body is divided into 12 visible segments, though unless the 
animal is fully extended one of the thoracic segments (numbers II 
to IV) is apt to be overlooked. The mouth-opening is on the first 
or head segment. This segment also bears a pair of small papille, 
known as antenne, and two pairs of small organs apparently sensory 
in function. The sensory organs and their nervous connections are 
figured by Keilin. The anus and posterior spiracles are on the twelfth 
(eighth abdominal) segment. 
There are minute hooklets irregularly scattered over the surface 
of the larva, but these are not easily seen except in eight bands of four 
rows each that lie on the ventral surface of the larva, at the anterior 
edge of each abdominal segment. In these bands the hooklets are 
larger and darker in color than over the rest of the body. There are 
several processes (‘‘pseudopodia’’) on the last segment—usually three 
with one or two papille on each. From the upper posterior part of 
this segment arise the posterior spiracular processes, each of which | 
bears a papilla on its upper surface. Each process ends in a chitinized 
tube that has at its tip three 
spiracular openings that are 
surrounded by very slender 
outwardly directed chitinous 
rays. When the larva is feed- 
ing it lies buried in the food, 
ve h only the tips of these Fic. 1.—Anterior spiracle of third-stage larva’ 
spiracular processes exposed enoeophiiencbes 
to the air. The rays around 
the openings evidently serve to prevent the openings themselves from 
sinking below the surface and thus cutting off the air-supply of the 
larva. A large trachea runs forward from each posterior gpiracle and 
connects with the anterior spiracle of the same side. Each of these 
tracheal trunks gives off numerous lateral branches, and not far from 
the anterior spiracles there is a large cross-connection between the 
two trunks. There is another cross-connection situated just anterior 
to the posterior spiracles. The anterior spiracle of Drosophila funebris 
is shown in figure 1. The same type occurs in all drosophiline larve 
that I have seen. It is chitinous, and may be extruded somewhat. 
The cephalopharyngeal skeletons or ‘‘jaws” of a few species are 
shown in figures 2, 3, and 4. These structures are jet black, except 
for the more posterior processes, which are brownish. The names of 
the parts that appear in figure 2 are from de Meijere’s account of 
D. obscura. All the parts shown in these figures are paired, and the 
