AQUATIC INSECTS IN NEW YORK STATE 413 
the dorsal surface having been removed. The maxillae are 
fleshy ovoid processes with a longitudinal row or terminal tuft 
of hairs, besides the long, loose hairs on the mesal surface. 
Attached to the base and projecting laterad is the palpus with 
its four or five terminal spurs or papillae. Forming the floor of 
the mouth cavity, and attached to the anterior edge or coales- 
cent with the sclerite which forms the lower surface of the head 
is the labium [p1.48, fig.4l]; a more or less triangular or semi- 
circular piece with a toothed margin. The ventral surface and 
margin is usually fringed with setae. 
The hypopharnyx is a toothed piece resembling the lower jaw- 
bone of a mammal, and lies tonguelike on the floor of the mouth 
cavity [pl. 48, fig.4h and pl.44, fig.6]. It is quite small and, being 
loosely attached, is easily torn away in dissection, hence some- 
what difficult to find. Attached to the posterior edge of the 
hypopharynx [pl.44, fig.5], and lying obliquely, with reference 
to the frontal plane, but perpendicular to the sagittal plane, is 
an elliptic flat ring. This ring is compound, made up of four 
lamellae in close contact, so that it appears at first sight as a | 
single ring; the surface of the lamellae is striated and fringed 
on the inner margin with long cilia. A portion of the front end 
of this ring is shown on plate 44, figure 5s. It appears to be 
the anterior margin of the gullet, and may perhaps act as a kind 
of sieve on which the food particles swept in by the rotatory 
fans, are caught. A second toothed piece [pl.44, fig.5¢] lies 
dorsad of the anterior lobe of the hypopharynx, and is probably 
aspart of it. 
The thorax is circular in outline, and wider than the head. 
In the full grown larva the sutures separating the three thoracic 
segments can not be distinguished. On its surface are tufts of 
long bristles, longer usually than those on the rest of the body. 
These bristles are feathered, though not so much so as in Anop- 
heles. The hairs appear to act as balancers. In addition to 
these hairs are a number of smaller, shorter tufts. 
The abdomen is five or six times as long as the thorax, but of 
much smaller diameter; consisting of nine segments counting 
the anal segment. The segments are subequal in length except- 
ing the first, eighth and ninth, which are frequently shorter. 
On the lateral margins are tufts of a few long hairs besides a 
few shorter ones, the arrangement of which may give specific 
characters, though, owing to the ease with which they fall otf 
in alcoholic specimens, they must be used as distinctive charac- 
ters with some caution. Projecting from the dorsal surface, 
near the posterior margin of the eighth segment, is a long, more 
or less cylindric tube, into which the two main respiratory 
