204 
Psyche 
[Vol. 93 
Diagnosis for adults of O. unicolor (Banks) s A. Fore wings rang- 
ing in colour from light yellow brown to dark brown; length of fore 
wing: male 14.5-18.5 mm; female 15-21 mm. 
Male genitalia (Figs. 2, 4). Segment IX not unusually short; 
inferior appendages variable in shape of segments, ventromesal 
angle of basal segment in ventral aspect ranging from obtuse (Fig. 
2c) to sharply pointed (Fig. 4b). Segment X with external branches 
tending to be orientated in an oblique to horizontal plane, usually 
narrowed basally and broader toward the apex; internal branches 
fused together into a flattened, somewhat pointed median lobe vari- 
ably cleft at the apex; inferior branches usually absent, occasionally 
represented by a small protuberance or angulate vertical lobe. Phal- 
lus with parameres variably fused to aedeagus, ranging from little 
separation (Fig. 2d) to almost complete separation (as in Fig. lid); 
spines at apex of parameres extremely variable, ranging from 1 to 6, 
usually straight and singlepointed. 
Female genitalia (Figs. 3, 5, 6, 7). Segment IX with enlarged 
tergal lobes uniformly bulbous; sternum IX reduced to a small 
sclerotized lobe at each side of the vulval lobe. Segment X in ventral 
aspect tapered and tubular, broadly open ventrally, dorsally entire 
or with a narrow median cleft, base of X extended into a lateral 
shoulder in ventral aspect, variable in shape and frequently dentate. 
Biology. Larvae of O. unicolor live in slow water and pool areas 
of cool rivers and streams, and also in the littoral zone of cool lakes. 
There appears to be little preference in substrate since larvae occur 
in stony streams and organic sediments of lake margins. Larvae 
usually burrow into bottom sediments for pupation, fixing the case 
to some larger object such as a rock. Collection records plotted by 
week for specimens examined (Fig. 10) are interpreted as a univol- 
tine life cycle. Most adults emerge in the period 15 July- 15 Sep- 
tember. Early larval development proceeds quickly, third instars 
appearing at least by early September, fourth instars by mid- 
September, with fourth and fifth instars overwintering. In contrast 
to Dicosmoecus (Wiggins & Richardson 1982, figs. 33, 34), no dia- 
pausing fifth instar larvae were found in O. unicolor. Pupae were 
collected from June to the middle of October. These data are similar 
to those from an intensive study of a population in Marion Lake, 
B.C. (Winterbourn 1971), except that most larvae overwintered 
there as instars III and IV; egg masses (4.5-5 mm diam., approx. 150 
eggs each) were found 9-24 September. 
