Beetles Identification Guide

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HISTERIDAE hister beetles
This group of beetles includes approximately 100 species in Canada.
They are found mostly under the bark of dead trees and in decaying vegetable
matter, carrion, dung, bird nests, and mammal nests. Both adults and
larvae are carnivorous.
Two species of histerids in Canada are more or less frequently associated
with rotten grain in granaries. They have no direct effect on the grain, as they
feed mainly on insects and mites. In addition to the species included here, two
species of Dendrophilus, D. xavieri Marseul and D. punctatus (Herbst), are found
occasionally in granaries and flour mills in Canada. Both species are probably
introduced, the first one from Japan, the second from Europe.
Carcinops pumilio (Erichson)
Diagnosis: The species is distinct from Gnathoncus nanus, the other histerid dealt
with here, in having the last exposed tergum about the same length as the preceding
one and by the presence of an anterior lobe on the prosternum.
Sexual dimorphism: Sexes are externally similar.
Distribution: Cosmopolitan but apparently more characteristic of temperate
regions. In Canada the species ranges from Quebec west to British Columbia.
Economic importance: The species has been recorded from Canadian cargo ships
carrying wheat (Aitken 1975). Armitage (1986) reported it as one of the most
conspicuous and abundant species in samples of droppings in poultry houses in
the United Kingdom. Geden and Stoffolano (1987) mentioned it as one of the
main predators of immature house flies in Massachusetts poultry houses.
Gnathoncus nanus (Scriba)
Diagnosis: The species differs from Carcinops pumilio mainly in having the last
exposed tergum distinctly longer than the previous one and by the absence of an
anterior lobe on the prosternum.
This species is similar to G. communis Marseul, another North American
histerid occasionally associated with stored food products. Adults of G. communis
differ from those of G. nanus usually by their larger size (length 2.5—3.5
mm), and by having the apical fourth of the elytra with faint microsculpture and
denser, more or less contiguous punctation. In G. nanus the elytral apex has no
microsculpture, and the punctation is sparser and clearly separated. Geden and
Stoffolano (1987) mentioned it as one of the main predators of immature house
flies in Massachusetts poultry houses.