AQUATIC INSECTS IX NEW YORK STATE 347 



ent planes and covered by the liair, tber are somewhat obscured. 

 The mandible is furnished with a dense fringe of hairs extend- 

 ing over its apex, more or less overhanging the teeth. Near 

 the base on the ventral side (the jaws moving in a horizontal 

 plane) is a fan of hairs whicli iirojeets mesad. at right angles 

 to the long axis of the mandible. A^entrad and mesad of the 

 mandible are the maxillae. The maxilla with its palpus pro- 

 jecting outwardly is shai)ed somewhat like a mitten, the pal- 

 pus representing the thumb [pl.30, flg.2]. Several long fringes 

 of hairs extending ce])halad and mesad, cover the surface of 

 the lacinia, among which is a single stout spurlike process. 

 On the palpus are a few scattered bristles, at its base usually 

 a small tuft of hairs, and its apex is provided with ])apillae. 

 The chitinous labrum is a short, somewhat semicircular shai^ed 

 piece overhanging the mouth, its plane being nearly perpen- 

 dicular to the long axis of the larva. Externally it is stiffened 

 by a T or Y shaiKHl brace, the stem forming a longitudinal 

 keel [pl.H3, tig.ll. and ])1..")(). tig..")]. Extending apically is a long 

 fringe of hairs, and back of the suture, combed backward and 

 outward, are long hairs. The apical margin is sometimes ser- 

 rate. The hypopharynx, through which the silk thread paissee, 

 is a rather complex structure; it consists primarily of two flat- 

 tened chitinized plates, connected by membrane, forming a flat- 

 tened tube [pl.37, fig.2]. At the apical (cephalic) end of this 

 is articulated a complex chitinous doubly arched segment with 

 two fringes of long, coarse hairs. The ventral plate is some- 

 what quadrangular in shape, widened cephalad, with its ante- 

 rior and posterior margins concave, and its lateral margins 

 sinuous. On its anterior margin, apically, is a transverse chi- 

 tinous comb [pl.36, fig.4]. The dorsal plate [pl.37, fig.2] is 

 composed of two triangular pieces joined on the center line. 

 On its apical (cephalic) edge is a transverse comb which projects 

 €ephalad and ventrad. This comb lies somewhat cephalad of 

 the comb of the ventral plate. The dotted lines of plate 36, 

 figure 4, mark the position of the dorsal plate. The ducts from 

 the silk glands [pl.37, fig.2] pass up between the two ])lates, the 



