AQUATIC INSECTS IN NEW YORK STATE 



413 



tlie 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 coalee- 

 ceut with the sclerite which forms the lower surface of the head 

 is the labium [pl.43, fig.4^] ; 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 [pi. 43, fig.4/t and pl.44, fig.6]. It is quite small and, being 

 loosely attached, is easily torn away in dissection, hence some- 

 what diflficult to find. Attached to the posterior edge of the - 

 liypopharynx [pl.44, figXl, and lying obliquely, with reference y~2^ <=■ 

 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, flg.Sf] lies 

 dorsad of the anterior lobe of the hypopharynx, and is probably 

 a part of it. 



The thorax is circular in outline, and wider than the head. 

 In the full grown larva the sutures separating the three thoracio 

 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 

 those 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 off 

 m 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 



