VOLUME 55, NUMBER 1 
11 
similarity of the genitalia of H. corbeti and H. separata suggest Nimmo is 
correct in regarding H. corbeti as a possible synonym of H. separata. 
The Larval Stage of Hydropsyche separata 
The most distinctive features of the H. separata larva are the pattern on 
the dorsum of the head, the prominent bump on the meson of the anterior 
margin of the anterior ventral apotome, the fine, branched hairs on the 
frontoclypeal apotome, the mandibles which have a deep lateral furrow 
bearing several setae and the relatively long, wide, scale-like setae on the 
abdominal terga. 
In the detailed description of the larva which follows, the terminology 
used is taken primarily from Wiggins (1977). 
General description .—Dorsum of head dark with lighter markings, sides 
and venter yellow, often with a pair of dark patches on venter. Rarely, head 
entirely dark except for region about each eye. Frontoclypeal apotome 
(Figs. 1, 5) slightly indented laterally; anterior margin convex, often with 
minute bumps along edge, minute branched setae on lateral portions of 
anterior margin; anterior portion of apotome with short scale-like setae be¬ 
hind anterior margin and on anterolateral surface but otherwise bare of such 
setae, often with large light oval area on middle; middle of apotome with 
V-shaped (Fig. 5) or lyre-shaped (Fig. 1) light area or rarely, light area 
absent, tentorial pits distinct, often four or five light muscle scars anterad 
of tentorial pits in a shallow, transverse depression; posterior portion of 
apotome with two to four light muscle scars in middle, structure illustrated 
in Figure 4 evident in cleared specimens within cuticle of apotome in light 
area near vertex of frontoclypeal apotome (structure approximately one- 
quarter as wide as the frontoclypeal apotome at level of seta 6) posterad of 
four muscle scars; posterior three-quarters of apotome covered with fine, 
branched setae (Fig. 2). Each parietal sclerite with numerous short scale¬ 
like setae and smaller, branched, fine setae (Fig. 3) on dorsal and lateral 
regions of anterior three-quarters of head (Fig. 1); pair of light muscle scars 
anterad of seta 16 (Fig. 1), a single light muscle scar above eye near fron¬ 
toclypeal suture, often several lighter muscle scars in posterior region of 
dorsum. Head setae 1 and 3 along anterior margin of frontoclypeal apotome 
(Fig. 1); seta 2 posterad of seta 1; seta 4 posterad of seta 2; seta 5 near 
posteromesal margin of tentorial pit; seta 6 near frontoclypeal suture at level 
of seta 16; setae 7 and 10 anterad of eye; setae 9 and 11 anterad and dorsad 
of eye; setae 12 and 14 posterad and ventrad of eye; setae (13 or 15?) anterad 
and laterad of seta 16; seta 16 posterad of pair of small muscle scars near 
frontoclypeal suture; seta 17 beside frontoclypeal suture where frontocly¬ 
peal apotome begins to narrow to posterior tip; seta 8 on lateral surface 
near anterior margin of head; seta 18 in middle of ventral surface of parietal 
