Flour Beetles are Just One Type of Stored Food Pest

By Chris Williams on February 17, 2015.

I just opened a new bag of wheat flour and found that it was loaded with little dark bugs. I threw it out of course. Do you know what these bugs were? Are they going to be in my other food? T. V., Dunbarton, NH

flour beetle in grains

Adult Flour Beetle

flour beetle larva

Flour Beetle Larva

It’s hard to identify your food pests without seeing one up close, but I would guess that your flour was infested by some kind of stored product beetle. Flour beetles are most likely, but they could have been drugstore beetles, cigarette beetles, or sawtoothed grain beetles. The habits of the beetles and the control methods are pretty much the same for each type of food beetle.

What Do Flour Beetles Look Like?

Adult flour beetles are flat, shiny, reddish-brown, and about 1/8-inch long. They’re active beetles, running to hide when disturbed. Adult beetles are found either in the food, on the outside of infested food packages, or on top of the food product. The wormlike flour beetle larvae are found burrowed into the infested food product. They are white to yellow-brown, slender and wiry, with a pair of dark, pointed projections at the rear. Larvae reach a length of about ¼-inch long. The other beetles I mentioned above are going to look very similar to the untrained eye and without magnification.

Potential for Infestation of Other Foods Exists

Your other foods could be infested, depending on how long the infested flour has been on your shelf and the condition of your other food items. Flour beetles can squeeze into all but the tightest packages. And, the larvae feed on a wide variety of foods, ranging from flour to cornmeal, crackers, cereal, dried fruit, spices, beans, even chocolate…100 different foods in all!

Food products that are older, with high moisture, and stored in warm conditions are the most likely to be infested. To check other foods, start with foods that you have had the longest, those that are past their “Use by date,” or those that have been forgotten in back corners.

If you want to be sure that your foods are okay and beetle-free, you’re going to have to check them (see How to Check Food Products for Insects – Advice From the Pros). This can be a tedious and messy job; some people opt for discarding suspect foods instead. Here’s a tip: Flour beetles, in high enough numbers, secrete chemicals that give infested food a pinkish-gray tint and a characteristic bitter taste and musty smell.

Call Colonial. We Can Help!

An exterminator can help you determine the seriousness and the extent of your food pest infestation. After you’ve cleaned out infested foods, you might want to have a Colonial Pest technician do an insecticide treatment of your food storage area to kill wandering beetles and eggs that have been laid on shelves.

For tips on how to avoid food pest infestations in the future, see Preventing Pantry Pests – Advice From the Pros and Don’t Bring Home Insects From the Grocery Store.

Top photo: Agricultural Research Service via Wikimedia, Public Domain
CSIRO [CC BY 3.0], via Wikimedia Commons



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