AQUATIC INSECTS IN NEW YORK STATE 435 
near the suture on the dorsal plate, the anterior pair quite close 
to the anterior margin [pl. 49, fig.8], and laterad of the posterior 
pair, lying close to the suture, but on the lateral plate is another 
seta. The median plate carries the labrum [Ir, fig.8], which 
hangs flaplike in front of the mouth and may be bent backward, 
and on its under surface are three pairs of setae. Attached 
to the labrum on its ventral surface is the epipharynx [fig.3e]. 
This is a complex structure attached at its anterior margin, its 
free margin projecting ventrad and caudad. On its surface are 
a number of spines, its margin is serrate and provided with 
three pairs of small serrate teeth. In addition to this is a pair 
of long, chitinized, sickle-shaped processes. The shape and the 
arrangement of the setae are as shown in figure 3. The lateral 
plates bear two pairs of rudimentary eyes (pigment spots), as 
well as the antennae and the jaws. The antennae [fig.2] are 
situated on the anterior end of the lateral plates; they are 
small, consisting of a comparatively long basal joint, on which 
are two terminal pieces, one four jointed, the other somewhat 
shorter and simple. The mandibles, situated ventrad of the 
antennae are stout and with a four or five toothed apical margin. 
Near the base, overhanging the teeth, is a brush of hair [fig.6 
and fig.8m]. The mandibles are articulated in such a manner 
that they move in an oblique plane, striking the labium |fig.8/ 
and fig.5l]. The labium is attached, or rather coalescent 
with the front margin of the ventral sclerite of the head, the 
suture separating this sclerite from the lateral ones only 
faintly marked. Miall & Hammond consider the ventral piece 
as a portion of the lateral sclerite. The margin of the labium is 
toothed, the three middle teeth somewhat shorter than those 
immediately laterad of them [fig.5J]. Near the base and ven- 
trad of the mandibles are the maxillae, consisting of fleshy 
processes, with forward projecting teeth on the lateral margin; 
a bunch of slender lobes and setae on the inner margin; and a 
short stout palpus with some terminal spines and papillae 
[fig.5me and fig.9]. On the ventral surface is a long stout seta. 
On each side of the labium is a striated and flexible fan-shaped 
flap which helps to close in the mouth [fig.5]. On the floor of 
the mouth cavity, lying close to the labium, is the hypopharynx. 
Its anterior margin is furnished with a number of short spines 
and bulb and platelike projections. This is the piece which 
Miall & Hammond, in their work on The Harlequin Fly, on page 
29, call the upper plate of the labium, or mentum in the figure 
on page 80. Its function seems to be that of a guide for the 
silk thread, as is undoubtedly the case with Simulium, The 
prothoracic pair of feet [fig.4] are furnished with a large num- 
ber of slender curved hairs, yellowish in color, the two feet 
