834 CHARLES PauL ALEXANDER 
on the surface of the water in the Illinois River. When submerged these 
larvae were very active, quite as noted in the account of R. mainensis. 
Larva.— In all general features like larva of R. mainensis (with the material available 
the writer is unable to point out differences). Present species a little larger than R. mainensis, 
measuring from 12 to 13 mm. in length and 1 mm. in diameter. Mouth parts and head 
capsule almost exactly like those of R. mainensis, already described. Antenna (Plate XXXI, 
134) with first segment elongate, a little enlarged toward tip, and with an elongate, thimble- 
shaped papilla at tip whose surface is delicately sculptured; surrounding this papilla at tip ~ 
of basal segment, a few microscopic tubercles and pegs; on face of basal segment on 
proximal half, a circular porous plate. 
Pupa.— Length, 7.8-8.8 mm. 
Width, d.-s., 1 mm. 
Depth, d.-v., 1.1-1.2 mm. 
Coloration light brown; abdomen paler, trivittate with dark brown; a broad, dorso-median 
line, and narrower, somewhat interrupted, pleural stripes; breathing horns yellow, darker 
at extreme bases. 
Cephalic crest (Plate XXXII, 137) low, the lobes divergent, their lateral angles with a stout 
seta which is directed cephalad. Just behind the anterior crest a much larger, low, appressed 
lobe, which is transversely wrinkled, bearing on its side a seta directed dorsad. Eyes rather 
large, widely separated by front; two setae on front between eyes. Labrum triangular, 
pointed at apex. Front a little elongated to provide for short rostrum of adult. Sheaths 
of maxillary palpi long, stout, almost straight. Labial palpi contiguous, lying side by side 
at tip of labrum. Antennae rather widely separated at their bases, ending just beyond 
wing root; in males lying across face of eye, due to the large size of eyes in this sex. 
Mesonotum prominent, carinate medially (Plate XX XIII, 142). Breathing horns long and 
slender, slightly curved, transversely crenulated, a little enlarged toward tips; proximo- 
cephalad of base of each horn a small rounded tubercle bearing two setae. Lateral angles 
of thorax with about three short setae. Mesonotum convex, transversely wrinkled, with 
a few very short setae. Wing sheaths ending about opposite posterior margin of second 
abdominal segment. Leg sheaths parallel, about subequal in length or those of fore legs a 
little longer, ending just before posterior margin of fourth abdominal segment. Dorsal 
abdominal segments (Plate XX XIII, 143) each with two narrow basal rings and a much 
broader posterior ring; ventral segments (Plate XX XIII, 144) with the two basal rings 
confluent; dorsal segments with each narrow basal ring having a narrow, slightly arcuated 
band of spicules, and posterior ring having a narrow basal band of spicules which is more 
or less arcuated, and a straight caudal band, immediately in front of which are four groups 
of two setae each, or, in some specimens, with the intermediate groups reduced to a single 
seta; ventral segments with posterior ring having a broad transverse band of spicules, 
with three setae in alinement at each end of this band; closer to base of segment, two 
strong setae on either side; anterior ring darkened, Pleura with large but apparently 
nonfunctional spiracles on segments 2 to 7, a strong ante-spiracular seta, and three post- 
spiracular setae, as illustrated (Plate XX XIII, 144). Male cauda (Plate XXXII, 139 and 
140) terminating in two acute tips which are directed dorsad; at base of these lobes on 
