Beetles Identification Guide

Distribution: Cosmopolitan and probably of North African origin (Halstead
1967). In Canada the species has been found in Nova Scotia, Quebec, Ontario,
and the Vancouver area.
Economic importance: Adults and larvae feed mainly on damaged and moldy
grain, showing a preference for wheat and oat products. They are found primarily
in granaries, flour mills, and warehouses. In Canada the species is only a
minor pest but is found regularly with primary grain pests such as species of
Sitophilus. It also occurs under the bark of trees, both in Europe and in North
America, where it has recolonized its natural habitat.
Palorus subdepressus (Wollaston)
depressed flour beetle
Diagnosis: The species is best separated from P. ratzeburgii in having the
genae clearly reflexed near the eyes and the anterior margin of the genae
rounded laterally.
Sexual dimorphism: Males have large, deep, setigerous punctures medially on the
second visible abdominal sternum (Faustini and Halstead 1982). Females have
only fine and diffuse foveae in that area.
Distribution: More or less cosmopolitan and based on morphological evidence
(Halstead 1967), probably originated in Africa. In Canada the species has been
found only in southern Manitoba.
Economic importance: The species is a minor pest in Canada. It has been found
occasionally in barns, granaries, and grain elevators in Manitoba since 1974 (Smith
1975). Like P. ratzeburgii, adults and larvae are found primarily on cereals and
their products. In the United States and India, the species is also found under
the bark of trees, where it has recolonized its natural habitat.
Tenebrio molitor Linnaeus
yellow mealworm
ténébrion meunier
Diagnosis: This species and its relative T. obscurus are readily separated from the
other tenebrionids dealt with here by their large size, which exceeds 10 mm. Adults
of T. molitor differ from those of T. obscurus mainly in having the punctation on
the clypeus, frons, and pronotum sparser, the elytra more parallel-sided, and the
body more or less shiny.
Sexual dimorphism: Males have the ventral angle at the apex of the fore tibia
extended into a small process; females have the ventral angle of the fore tibia
rounded (Fig. 259).
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