Entomology of the Illinois Rvoer, 269 



The larva is about 9 mm. long, white, posterior pro- 

 longations of head not long, abdominal segments, except 

 first and last, with anterior transverse ridge beneath, 

 bearing in front, each side, a row of small double-pointed 

 teeth, with an arc of minute teeth at inner ends of 

 rows; back of each row a series of oblique rows of small 

 teeth, the inner ones converging at median line, and be- 

 tween their tips a larger truncate tooth; last segment 

 with longitudinal anal slit, two rows of minute teeth 

 each side, four scabrous elevations in front, and a U- 

 shaped line of teeth each side, all the teeth clear tes- 

 taceous. Apex of last segment bluntly rounded off, a 

 small deeply concave area at center containing the light 

 brown stigmata, a low tubercle exterior to each, and 

 an approximate pair of short teeth below. 



Larva (5). 



There seems to be no question as to the aquatic habit 

 of this species, as examples were taken March 27, 

 with dip-net and sieve, from the mud at the bottom of 

 the main river, not far from the channel, in several feet 

 of water, off the south end of the city. One larva was 

 found also March 22 in Quiver Lake, at Station B, lying 

 exposed in a few inches of water. 



In general appearance it is like the preceding, 12-13 

 mm. long, whitish, transparent and glassy, the black 

 posterior prolongations of the head quite long and 

 straight, diverging at tip ; the anterior transverse ridges 

 of the abdominal segments crossed by glassy lamellar 

 raised edges, their posterior ends, especially of the inner 

 ones, extended inwardly toward the median line, each 

 elevated near its middle into a triangular saw-tooth, 

 with acute apex and vertical serrulate posterior edge; 

 posterior truncation encircled by seven broad concave 

 membranous teeth with thin transparent edges, two 

 large ones at the lower angles, a pair of small double- 

 pointed truncate lateral ones, two medium-sized ones 

 at the upper angles, separated from those below by a 



