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.

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

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

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 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.