Biscuit Beetles

How to spot them

Biscuit beetles are small reddish-brown beetles 2 to 3 mm long. They are relatives of the woodworm beetle and may sometimes be mistaken for woodworm due to their similar appearance.

Habits

They commonly infest hard, dry, starch-containing foods like cereals and spices. They are very clever at entering packages that are not tightly closed, and can bore through plastic bags, foil and cardboard to reach preferred foods. Its American name 'drugstore beetle' comes from its ability to breed in dried vegetable matter of any kind, even poisonous substances such as strychnine, belladonna or aconite.

Biscuit beetles are found throughout the world, and are likely to have been spread by ships in former times. The old sailor's habit of tapping a ship's biscuit on the table before eating was to knock out some of the beetle larvae and similar insect infestations!

They are not dangerous, but they can be a nuisance when they infest a food cupboard, and if left long enough, they can produce some quite spectacular infestations in old packets of cereal and the like. They are also often associated with old bird nests in roof spaces.

As they are so tiny they may come in unnoticed in a food packet and spread to infest the rest of the cupboards, or they may travel from another location, like an old bird's nest.

Life cycle

Female biscuit beetles will lay eggs freely either in a preferred food product or in crevices near to it. When conditions are warm enough (they need 20ºC or more - this is average room temperature) the eggs will hatch into larvae ½ mm long which wander around the surrounding area, crawling through tiny spaces to reach foodstuffs. They can survive starvation for up to 8 days while looking for food. After about 2 months, depending upon the temperature, the larvae pupate in cocoons, often within the food, until 1 or 2 weeks later the adults hatch. The adults bore their way through food or packaging to emerge, making holes which can look rather like woodworm.

The adult beetles do not eat, instead they wander about for 3 to 4 weeks, during which time they will breed and lay more eggs. They will often wander far from the original site, and may be found on work surfaces and other locations around the room. They may sometimes be found on window frames, where they are attracted by light. They are strong fliers.

Control

The first thing to do is empty food cupboards, trace the infested food, and dispose of all the infested food you can find. They prefer hard, dry starchy products, although they can eat almost anything organic if required, and can penetrate sealed packets and tin foil. They may also be found in screw topped jars if these have not been properly closed. The kind of foodstuffs which might be attacked are:

• cereal products
• nuts and spices
• biscuits
• packet soups and drinks
• dog biscuits and chews
• dried meat
• dried vegetables
• pasta

Items you are not sure about are best disposed of or sealed in plastic containers or screw-topped jars (tightly closed!) and left for a few months. If there is no activity within about four months it is probably not infested. This ensures that any new food that you buy is not re-infested by accident.

When the cupboards are emptied thoroughly clean down all the surfaces, paying particular attention to corners and crevices. Then spray the surfaces with an insecticide for use with crawling insects, again, making sure that you reach the corners. Try to get an insecticide with a 'residual' effect, and make sure that it is approved for use in food rooms (the can label should state this).

After the spray has dried, and has been left for any period stated on the can, you can put food back into the cupboard. Try to store newly bought starchy items such as flour, rice or biscuits in sealed containers so that they cannot be attacked by any beetles missed by the insecticide. Make sure that you rotate stocks to use up old items first and dispose of anything past its sell by date.

If the beetles are in areas other than the kitchen, particularly on the first floor, it is likely that they are travelling from a bird's nest in the vicinity. Check the loft space and make sure that there are no old bird's nests which might be harbouring the beetles. If there are, carefully remove and dispose of them and thoroughly spray the area with a residual insecticide for use with crawling insects.

Safety

Be safe. Always read the label of an insecticide before deciding to buy it and follow the safety precautions during use. Some are flammable, hazardous to pets (especially fish) or harmful if breathed in. Do not spray foods, food preparation surfaces or animals. Never spray around children. Do not breathe in excessive amounts of spray.