Spider beetles
Ptininae species


Secondary pest: Grain feeder and scavengers
Order: Coleoptera
Family: Anobiidae
Acronym: PTI


  • Adults superficially resemble small spiders upon first glance.
  • Adults vary in color and may be hairy or devoid of hair.
  • Adults range in size from 2 to 4.5 mm long.
  • Head is completely or mostly hidden when viewed from above.
  • Antennae are very long and similar in length to the legs, giving a spider-like appearance.
  • Larvae are white and grub-like in appearance with a well-developed head and thoracic legs.

Similar species

  • None

Commodities affected

  • Preferred commodity may depend on species
  • Cornmeal, bran seeds, grain, spices, grain dust, fishmeal, warehouse sweepings, flour, ground oats, ground barley, wheat meal, rolled oats, stored grain near the surface
  • Readily feeds on sound wheat and rye

Signs of infestation

  • Contamination with silk, accumulation of granular materials, presence of adults and silken cocoons


  • Do not create distinctive damage
  • Webbing associated with milled products often reduces grain quality to that of feed
  • Larvae may feed in a cluster and web together kernels
  • Presence of spider beetles is an indication of poor sanitation


Geographic range

  • Approximately 20 species are found in Canada, with more in British Columbia than any other province.
  • Certain species are more prevalent in certain locations.
  • Most are generalist scavengers feeding on wide variety of materials of plant and animal origin but some species are more specific in their food preferences.
  • Pseudeurostus hilleri is widespread and may be found in granaries and warehouses.
  • Ptinus fur is widespread.
  • Ptinus ocellus is most important in British Columbia and may be found in terminal grain elevators, mills, warehouses.
  • Ptinus raptor is most abundant in warehouses in New Brunswick and Nova Scotia and is the most common spider beetle in Ontario.
  • Ptinus villiger is found coast to coast in dwellings, granaries and other locations and causes the greatest losses of stored products.

Life history

  • Life history varies by species, but spider beetles generally prefer higher humidity areas.
  • Many species are adapted to lower temperatures (reproduce as low as 10°C).
  • Development time varies with time and species.


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Did you know?

The family contains about 450 species.