These tiny beetles have a wildly indiscriminate diet, and notorious relatives, but from some angles barely resemble beetles at all. Would you be able to ID an Australian spider beetle?
Common name: Australian spider beetle
Scientific name(s): Ptinus tectus, or Ptinus ocellus in some sources. Currently in the family Ptinidae, but previously classified as Anobiidae or Bostrichidae. Their relatives include furniture beetles, cigarette beetles, drugstore beetles and deathwatch beetles.
Description: Spider Beetle larvae are C-shaped, up to 3 mm long, whitish with a brown head capsule, and hairy. They pupate in spherical thin-walled cocoons, frequently in chambers excavated into wood near the food supply. Adult beetles are 2.5-4 mm long, reddish-brown with yellowish-brown hairs, and have their head tucked underneath the thorax, a narrow waist, and a large rounded abdomen. This combined with their long legs gives them a vague resemblance to a spider or large mite, from which they derive their common name. Approximately 1000 sticky eggs will be laid on or near their food.
Geographic distribution: The Australian spider beetle originally lived in Tasmania and New Zealand, but by 1900 had been introduced to Europe and the UK where it promptly out-competed their native spider beetles. Since then is has become a worldwide pest.
Habitat: In the wild, Ptinus tectus is most frequently found inside bird nests and animal lairs, but inside buildings may be found in pantries, kitchens, wardrobes, roof cavities, or anywhere else their food is available. Australian spider beetles have a life cycle of approximately a year, and the adults may be active at temperatures down to 2 °C. However, reproduction and larval development stops below temperatures of 10 °C, and above 28 °C.
Pest status: Australian spider beetles have an amazingly wide diet, including dead insects, dry carrion, all kinds of plant products, museum specimens, old wood, textiles (including silk and wool), rodent droppings, fish food, drugs, and books. The adults and larvae will chew circular holes in packaging to access food, chew their way out again to pupate, and chew holes in timber to pupate, or build their cocoons attached to packaging.
Treatment: Infestations often originate in bird nests, which should be removed. Roof and wall cavities may be fumigated. Within domestic or commercial buildings, infested products should be removed and destroyed, any sources of humidity controlled, preparation areas kept clean, and any food products kept in resealable containers. Residual pesticides rated for beetles or stored food pests should be applied at wall and floor junctions, and repeated after 3 months to catch any newly emerged adults or larvae.
There are a range of spider beetles in Australia, some of which look quite different, such as the smooth spider beetles.
Image credit: Clare McClellan, Museums Victoria
Daniel Heald, technician and entomologist
Free for use under the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0).
Credits:
Main image: Clare McLellan Museums Victoria
Female Australian spider beetle: Simon Hinkley & Ken Walker Museums Victoria
