The drugstore beetle, Stegobium paniceum, is a globally distributed insect and a common pest of stored food products. This small, reddish-brown species feeds on dry, organic matter, making it a persistent nuisance in commercial facilities and residential pantries. While adult beetles do not feed much, their presence indicates a destructive problem caused by their larval stage. Controlling this pest requires removing all life stages and preventing future outbreaks.
Identifying the Drugstore Beetle
Adult drugstore beetles are tiny, measuring about one-eighth of an inch (2.25 to 3.5 mm) in length, with a cylindrical, humpbacked body shape. They are uniformly light brown to reddish-brown and covered in fine, silky hairs. A distinguishing feature is the antennae, which end in a distinct three-segmented club, setting them apart from the closely related cigarette beetle.
The beetles possess fine grooves that run lengthwise along their wing covers (elytra), giving them a striated appearance. The female lays up to 100 eggs on or near a suitable food source. These hatch into the damaging life stage: a small, cream-colored, C-shaped larva, often described as a grub.
The larva tunnels through the product for several weeks, causing the majority of material damage. Once fully grown, the larva builds a cocoon of silk and food particles to pupate within. The entire life cycle, from egg to adult, can take as little as 40 to 50 days under ideal conditions, such as 85°F (30°C), allowing for multiple generations per year.
Range of Consumed Materials
The drugstore beetle earned its name from its tendency to infest pharmacies and apothecaries, consuming dried herbs, spices, and medicinal products. This pest is a general feeder, capable of attacking a wide variety of dry plant and animal products.
Infestations commonly occur in both food and non-food items. In their search for new food, adult beetles can chew through materials like cardboard, plastic films, aluminum foil, and thin sheets of lead.
Common Infested Materials
Flour, pasta, breakfast cereals, and dried fruits
Spices, such as pepper and paprika
Dried pet foods and tobacco
Museum specimens, leather, wool, and books
The primary damage results from extensive contamination, not just consumption. Larval tunneling, insect fragments, fecal matter (frass), and exoskeletons render the infested product unfit for consumption. Infested packages often show tiny, circular “shot-holes” where newly emerged adult beetles have chewed their way out.
Eliminating and Preventing Infestations
Eliminating an infestation begins with locating and removing the infested material. Any product showing signs of beetles, larvae, or exit holes must be discarded outside the home in a tightly sealed bag. Following disposal, storage areas like pantries and cabinets require extensive cleaning.
Use a vacuum cleaner with a crevice tool to remove debris hiding in corners and cracks. After vacuuming, wipe down all shelves with warm, soapy water to remove residual eggs. Heat and cold treatments are effective non-chemical methods for salvaging dry goods.
To kill all life stages, place items in the freezer at 0°F (-18°C) for at least four days, or heat them to 120°F (49°C) for a minimum of four hours. Prevention relies on storing susceptible foods in air-tight, hard-sided containers made of glass or durable plastic. Practicing stock rotation, using the oldest products first, reduces the time food remains vulnerable to infestation.