MAY FLIES AND ISIIDGES OF NEW YORK 181 



the sclerite from the lateral ones onl}' faintly marked. Miall and 

 Hammond (1900) consider the ventral piece as a portion of the 

 lateral sclerite. The margin of the labium is toothed (pl.22, 

 fig.l 1) ; the size and arrangement of the teeth vary in the different 

 species. Near the base and ventrad of the mandibles are the 

 maxillae (fig.l mx) consisting of fleshy j)rocesses, with a short 

 cephalad projecting palpus (fig.l p), and some setae and papillae. 

 On each side of the labium is a striated and flexible fan-shaped 

 flap which helps to close in the mouth. On the floor of the mouth 

 cavity, Ij'ing close to the labium, is the hypopharynx (fig.l hy), 

 with various setae and papillae. The prothoracic pair of feet is 

 furnished with a large number of slender, curved hairs, some- 

 times pectinate, the two feet very close together so that they 

 appear almost as one (pl.21, fig.8). The first three segments of 

 the body in specimens which are ready to transform are enlarged 

 and represent the thoraxj the intermediate segments of the 

 abdomen are subequal in leng-th and usually have a few setae. On 

 the ventral surface of the eleventh segment of those species which 

 are blood red in color there are two pairs of long blood gills 

 pl.lG) ; on the caudal end of the dorsal aspect of the last segment 

 are two small papillae each surmounted by a tuft of a few long 

 hairs; ventrad of these there is a bunch of four short blood gills. 

 The anal feet are about as long as the eleventh segment, each one 

 with a crown of from 10 to 20 bifid claws (pl.21, fig.9). 



Pupa. The pupa is somewhat elongate, the thorax enlarged, 

 and the abdomen 8-segmented, not counting the anal appendages 

 (pl.16 and pl.23, fig.9). Upon the cephalic end of the thorax are 

 the respiratory organs, which ma}' consist of a pair of much 

 branched filaments, or a pair of tubes or knobs, or may be entirely 

 wanting. On the abdomen there are frequently a fcAv lateral fila- 

 ments, and at the caudal end of the lateral fins of the eighth seg- 

 ment there is often a chitinized comb or spur (pl.22, figs. 8 and 

 20) with a variable number of teeth depending upon the species. 

 Usually the dorsum of each abdominal segment is marked by a 

 large number of short and very minute setae arranged in some 

 constant pattern for a given species (pl.22, figs. 3, 12, 13, 14, 15). 

 The ninth or anal segment may be provided with a fringe of 

 matted hairs, forming a paddle, or may have only a few charac- 

 teristic setae. 



