MAY FLIES AND MIDGES OF NEAV YORK 30 



of the net; aud when by climbing- on a big rock in tlie opening I 

 captured a netfull of them I found they were all males. About 

 the same time also subimagos swarmed into my trap lanterns 

 that overhung Fall creek, and a few imagos with them. 



The nymph. (PI. 7. flg.2.) Length, 7 mm.; antennae, 3 mm., 

 and setae, 7.5 num. additional. Body strongly depressed, widest 

 across the rather prominent mesothorax. Head flattened above; 

 eyes round, prominent, situated just before the hind margin. 

 Antennae situated midway the length of the head, which before 

 them is pilot shaped, dilated at the sides and sharp-edged. Ocelli 

 three, rather large, situated in a nearly straight transverse row 

 in the male, in a triangle in the female. Labrum half as long as 

 broad, widened anteriorly, rounded on the anterior angles and 

 deeply emarginated in front, where fringed with short stiff bris- 

 tles (pl.8, fig.o). Mandible (])1.8, flg.B) stout, its two canines each 

 tridentate on tip, its ipalp deeply bifid ; on the inner margin just 

 before the molar surface is a low conic tubercle. Maxilla (pl.8, 

 fig.4) short and stout, the ipalpus two-jointed, the consolidated 

 galea and lacinia squarish, the tip of the former ending in a long 

 and distinctly pectinated spine, the inner and distal margins 

 densely fringed with slender hairs. Labium (pl.8, flg.3) with 

 three jointed palpi, the broad galeae and the narrow laciniae with 

 their tips on a level, and densely fringed with spinules, the spin- 

 ules on the laciniae being stouter. 



Thorax depressed, increasing in width to the bases of the wings. 

 The wing cases reach the base of the fifth abdominal segment. 

 The legs are rather short and stout, with flattened and dilated 

 femiora and slender tibiae, pale with a more or less complete 

 brownish ring beyond the middle of the femora and some fainter 

 markings at the knees. 



Abdomen depressed, regularly tapering from the third seg- 

 ment to the end, segments slightly increasing in length to the 

 ninth, the tenth somewhat more than half as long as the ninth, 

 produced above in a rounded lobe with a narrow blackish border 

 that is interrupted by paler in the middle of the margin. There 

 are sharp, triangular lateral spines on segments 4-9, increasing 

 in length and sharpness on the succeeding segments, represented 

 on segments 2 and 3 by mere angles of the flat margin, on 8 one 

 fourth as long as the segment. Gills very peculiar; on segment 1 

 a simple linear or slightly tapering filament (pl.8, flg.7) that is 

 fully as long as the succeeding lamellae; on 2-7 double, lamelli- 

 form, Avith pinnately branching tracheae; each of the pair of 

 lamellae is typicall}' three-lobed ; the middle lobe of the upper- 

 most lamella is itself lamelliform, oval or oblong, separated by 



