Beetles Identification Guide

from seeds in stores but are unable to reinfest dried seeds; they have to gain
access to ripening pods in the field to reproduce. A few species, however, are
associated with stored products. In such cases the adults can reinfest dried seeds
and produce successive generations.
Besides the species included here, two species of Callosobruchus, C. chinensis
(Linnaeus) and C. maculatus (Fabricius), are found occasionally in imported beans
in Canada. These Callosobruchus species differ from Acanthoscelides obtectus and
Bruchus pisorum in having a distinct tooth on both the upper and lower margins
of the hind femur.
Acanthoscelides obtectus (Say)
bean weevil
bruche du haricot
Diagnosis: The species is easily differentiated from Bruchus pisorum, the other
bruchid included here, by its smaller size and in having a large tooth, followed by
3—4 smaller teeth, on the lower margin of the hind femur and no tooth on the
upper margin.
Sexual dimorphism: Males have the last exposed abdominal sternum emarginate,
its length being shorter than the length of the previous sternum at the middle;
females have the last sternum subemarginate, the length at the middle being as
long as that of the previous sternum (Fig. 242).
Distribution: Cosmopolitan. In Canada the species has been found from
Nova Scotia west to British Columbia but can survive winter conditions only
in a heated environment.
Economic importance: The species is a well-known pest of beans, particularly
those of the genera Phaseolus and Vigna. In Canada it is found mainly in association
with stored beans, although infestations of growing crops have been reported
(Campbell et al. 1989). The damage is done by the larvae, which feed
inside the beans.
Bruchus pisorum (Linnaeus)
pea weevil
bruche du pois.
Diagnosis: The species differs from Acanthoscelides obtectus, the other economically
important bruchid in Canada, by its larger size and in having a
large tooth on the upper margin of the hind femur and usually a small tooth
on the lower margin.
Sexual dimorphism: Males have a spine-like projection at the apex of the median
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