The Drugstore beetle (Stegobium paniceum), also known as the Bread beetle or Biscuit beetle, is a tiny, brown beetle that can be found infesting a wide variety of products, and is among the most common non-weevils to be found there. It is the only member of the monotypic genus Stegobium.
They have a worldwide distribution and can be more commonly found in warmer climates. They are similar in appearance to the Cigarette beetle (Lasioderma serricorne), but are slightly larger (adults can be up to 3.5 mm in length). Additionally, Drugstore beetles have antennae ending in 3-segmented clubs, while Cigarette beetles have serrated antennae (notched like teeth of a saw). The Drugstore beetle also has grooves running longitudinally along the elytra, whereas the Cigarette beetle is smooth.
Their larvae are small, white grubs, and they can be distinguished from the grubs of the Cigarette beetle by their shorter hair. The female can lay up to 75 eggs at once, and the larval period lasts up to several months depending on the food source. It is the larvae that are responsible for most of the damage that this species can cause.
The Drugstore beetle lives in obligatory symbiosis with a yeast fungus, which is passed on to the offspring by covering the eggs with it.
As their name suggests, Drugstore beetles have a tendency to feed on pharmacological products, this is from their preference of dried herbs and plant material sometimes used as drugs, e.g. they have been known to feed on Strychnine, a highly toxic herbal extract. They will also feed on a diverse range of dried foods and spices, as well as hair, leather, books, and museum specimens. They can bore into furniture, and in some cases tin foil or sheets of lead. Also known as Biscuit or bread beetles since they happily live on biscuit or bread crumb.
The most effective method of ridding a home of these pests is to try to discover the source of the infestation.
Once this has been found, efforts can be made in removing the root of the problem, which is usually related to bird nests, food and high humidity levels. Therefore steps will have to be taken in removing any birds' nest from the premises (if this is the situation then ideally specialist advice should be sought), food residues and any food which has been left open; these steps should be followed by adopting measures to decrease the humidity levels; perhaps by way of a dehumidifier.
Once satisfaction has been reached in removing the main cause of the infestation, the immediate area of the outbreak should be cleaned thoroughly with a vacuum cleaner, paying special attention to small cracks and crevices; ideally the area should be treated with an effective insecticide, too.
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- Cornell Cooperative Extension Fact Sheet
- drugstore beetle on the UF / IFAS Featured Creatures Web site