AQUATIC IXSECTS IN XEW TOEK STATE 435 



ntar the suture on the doi-sal plate, the anterior pair quite close 

 to the anterior margin [pi. 49, fig.8], and laterad of the posterior 

 pair, lying close to the suture, but on the lateral plate is another 

 eeta. The median plate carries the labrum [Ir, flg.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 [flg.Se]. 

 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 [flg.2] are 

 situated on the anterior end of the lateral plates; they are 

 small, consisting of a comparatively long basal joint, on whieli 

 are two terminal pieces, one four jointed, the other somewhat 

 shorter and simple. The mandibles, situated ventrad of the 

 antennae are stent and with a four or five toothed apical margin. 

 Xear the base, overhanging the teeth, is a brush of hair [fig. 6 

 and fig.8;j(]. The mandibles are articulated in such a manner 

 that they move in an oblique plane, striking the labium .[fig.SJ 

 and flg.SJ]. 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.5Z]. 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.Smo! 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 [flg.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 30. 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 [flg.4] are furnished with a large num- 

 ber of slender curved hairs, yellowish in color, the two feet 



