1986] 
Wiggins & Richardson — Onocosmoecus 
213 
straight, and the apical membranous lobe is also reduced. The fused 
internal branches of segment X are more flattened than in the typi- 
cal form and the median crest less distinct; the external branches of 
X tend to be straight-sided and less tapered than in the typical form, 
but are enlarged apically in one specimen in the Shasta County 
series. Females of this variant are similar to the typical form. 
None of these variant specimens is included in the type material of 
O. sequoiae, and in the continued absence of intermediates, they 
could be considered as representing a distinct species. 
Key to adults of Onocosmoecus s.s. species 
1 Males 2 
Females 3 
2(1) In lateral aspect, inferior branches of segment X large and well 
developed into a flattened tongue between the external branch 
and subanal plate, external branches of X largely orientated in 
a vertical plane, frequently broadest at the base and tapering 
apically (Fig. 11a). Known only from the Sierra Nevada 
Mountains of eastern California (Fig. 14) sequoiae 
In lateral aspect, inferior branches of segment X usually lack- 
ing, occasionally present but very small, external branches of X 
oriented more horizontally, frequently narrow at the base and 
broadened apically (Fig. 2a). Widely distributed in North 
America including California (Fig. 14) and also far eastern 
USSR unicolor 
3(1) Segment IX with terga enlarged and bulbous, segment X in 
ventral aspect a tapered tube, open ventrally but closed dor- 
sally for the most part or with a narrow apical cleft (Figs. 3, 5, 
6, 7) unicolor 
Segment IX with terga enlarged but concave ventrolaterally, 
segment X in ventral aspect tubular but tapered apically little if 
at all, and cleft both dorsally and ventrally in a broad V-shape 
(Fig. 13) sequoiae 
Acknowledgments 
This study was completed under financial support (to GBW) from 
the Natural Sciences and Engineering Research Council of Canada. 
Field studies were supported by previous grants (to GBW) from the 
