Beetles Identification Guide

PTINIDAE spider beetles
About 15 species of this family are currently known in Canada. They are
usually found in nests of mammals, birds, or bees, on dry carrion, or more commonly,
indoors. Adults and larvae are scavengers that feed on a wide variety of
dried animal and vegetable materials. Members of the family are commonly called
spider beetles because of the superficial similarity of the adults of some species
to small spiders.
Most ptinids occurring in Canada are minor pests in empty granaries, mills,
warehouses, and dwellings, where they feed mainly on grain, flour, dried fruit,
spices, and decaying animal and vegetable refuse. Their presence is often indicative
of poor sanitation, with accumulations of residues. A few species have been
reported to bore into wood to form pupal chambers. A few others are known to
attack collections of dried insects and plants.
Gibbium aequinoctiale Boieldieu (synonym: G. psylloides auct.)
Diagnosis: The species is distinctive among the ptinids dealt with here in having
the pronotum and elytra devoid of vestiture and punctation.
This species has been reported in many parts of the world, including North
America, as G. psylloides (Czenpinski). Recently, Bellés and Halstead (1985),
following Hisamatsu (1970), pointed out that the common stored-product species
of Gibbium is G. aequinoctiale and that G. psylloides is a Palaearctic species
most frequently found in the Mediterranean region. Adults of the two species
differ mainly in the shape of the antennal fossa and the dorsal carina on the median
lobe of the male genitalia (Bellés and Halstead 1985).
Sexual dimorphism: Males have a tuft of dense setae on the middle of the
metasternum (Fig. 266). Such a tuft is absent in females.
Distribution: Cosmopolitan but more common in subtropical and tropical regions.
In Canada the species has been found in Nova Scotia, New Brunswick,
southern Quebec, and southern Ontario.
Economic importance: In Canada the species is found in flour mills and occasionally
in warehouses and hospitals.
Mezium affine Boieldieu
shiny spider beetle
ptine luisant
Diagnosis: The species is readily distinguishable from the other ptinids discussed
here in having the pronotum densely hairy and the elytra devoid of punctation
and vestiture, except for a narrow basal collar of golden setae and sometimes a
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