Beetles Identification Guide

may eventually become more important. Barak et al. (1981) noted that in recent
years, it has developed into a significant pest of stored shelled corn in Minnesota.
Adults and larvae prefer stored products of plant rather than animal
origin, with a preference for corn over other grains; unlike many tenebrionid pests,
they attack sound grain. In Canada the species has been found in small numbers
in granaries and sometimes in large numbers inside poultry houses. Under natural
conditions, C. angustus occurs in the decaying interior of the agave flower
stalk (Dunkel et al. 1982).
Gnatocerus cornutus (Fabricius)
broadhorned flour beetle
Diagnosis: Males are distinctive among the tenebrionids dealt with here by the
structure of the head: each mandible bears a conspicuous, flattened, dorsal projection,
the anterior margin of the head is swollen and sharply sinuate, and the
frons has two small, triangular protuberances. Females, which have no projection
on the mandible or protuberances on the frons and have the anterior margin
of the head rounded, are superficially similar to members of Tribolium. They
differ from the species of Tribolium discussed here in having the lateral bead of
the pronotum continuous over the anterior margin and the intercoxal process of
the prothorax parallel-sided.
Sexual dimorphism: As stated in the diagnosis.
Distribution: Cosmopolitan. In Canada the species has been found from Nova
Scotia west to Manitoba and in British Columbia.
Economic importance: This species is a minor pest of cereal and animal products. In
Canada it has been reported mainly in flour mills and warehouses; the species can probably
survive winter conditions only in heated buildings.
Palorus ratzeburgii (Wissmann)
smalleyed flour beetle
Diagnosis: This species and its relative P. subdepressus are distinctive among the
tenebrionids dealt with here in having the eye entire, not incised by the side margin
of the head. Adults of P. ratzeburgii differ from those of P. subdepressus mainly
in having the genae and the frons at the same level near the eyes and the anterior
margin of the genae somewhat angulate laterally.
Sexual dimorphism: Males have large, deep, setigerous punctures on the median
part of the second visible abdominal sternum (Faustini and Halstead 1982). Females
have fine and diffuse punctures medially on the second abdominal sternum.
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