1974] 
Cooper — Boreus 
97 
mated pair together that, unless the male’s grip is loosened, the female 
cannot free herself. In all but B. notoperates , the female is then 
rocked forward into the final female vertical position. Although the 
spines of the epandrial bosses may once again act against denticles of 
the gonapophyses’ blades, preventing slippage, and the male’s wings 
give an added grip, the change in position seems a supererogation so 
far as security of the male’s mating grip is concerned. 
The aedeagus, at rest, lies within a chamber that may be distin- 
guished from the endandrium. The roof of the aedeagal chamber is 
the band-like sclerotization over the aedeagus which forms the floor 
of the endandrium; the side walls are in part defined by the internal 
faces and musculature of the gonocoxites, and the floor of the chamber 
by the cephalad-directed apodemal band from the antero-medial, 
ventral angle of each gonocoxite that joins its homolog as a broaden- 
ing, very thin strap, the ventral gonobase (fig. 2B) which, in some 
specimens, encloses a minute medial sclerotized plaque. The space 
enclosed between the dorsal and ventral gonobases, then, forms the 
genital chamber proper, and the endandrium and aedeagal chambers 
are thus dorsal and ventral subdivisions of it. 
The aedeagus itself is a heavily muscled tube containing the un- 
paired ejaculatory duct. At rest it is hook-shaped, with its hooked 
tip wholly withdrawn into the aedeagal chamber, resting upon the 
ventral adductor muscle (fig. 2B). The paired ejaculatory ducts 
separately enter the caudal end of the aedeagus (figs. iC, 2A, B), 
uniting within it. Above the aedeagus is the sclerotized band that 
serves as floor to the endandrium. Below, near the point at which 
the aedeagus bends back on itself in its distal third, there is a slender, 
sclerotized hoop which partially encircles the aedeagus on the ventral 
side, from which a fan of muscles extends dorsally and caudally to 
insert on the dorsal sclerotized band. In B. borealis Banks , 9 and 
B. coloradensis Byers, there is both a dorsal and ventral sclerotized 
longitudinal band between which the aedeagus lies. 
The contraction of the muscles running from the ventral hoop to 
the floor of the endandrium both enables the aedeagus to be held and 
packed in retraction within the genital chamber and, when the 
aedeagus is everted, to reduce the space of the aedeagal chamber and 
thus force the aedeagus caudally outward. No doubt, to judge from 
the anatomical relations of the endandrium, the initial downward 
The Whitney’s field-notes suggest that Banks, when describing B, borealis, 
had but two of a total of four specimens that were captured; see records 
129 and 157, pp. 136-137, in McAtee (1923). 
