Insect of the Month: Drugstore Beetle
This month, we’re spotlighting the Drugstore Beetle (Stegobium paniceum) — a common but often overlooked pest in stored product environments. These small reddish-brown beetles are known for their broad diet and ability to infest everything from flour to pharmaceuticals. Understanding their habits, life cycle, and signs of activity can help prevent product loss and costly infestations.
What do Drugstore Beetles look like?
- Adults: Up to 3.2 mm (0.125 inches) long, brown to reddish brown. Similar in appearance to Cigarette beetles but has several rows of pits (striated) on hairy elytra (hardened wings). The last three antennal segments are slightly enlarged and elongated.
- Eggs: Not readily visible without magnification. Eggs are slightly oval in shape, whitish in color, satin to glossy sheen, and approximately 0.2-0.5 mm (0.019 inches) long.
- Larvae: Creamy white, C- shaped, slightly hairy, with a large distinct head, and three pairs of thoracic legs.
- Pupae: Pupal cases whitish; inside a pupal chamber within food material.
What is the Drugstore Beetle life cycle?
The female beetle will lay eggs in almost any dry organic substance. Larvae will tunnel through the food substance for about 4-5 months. The life cycle on average is seven months but can be as short as two months. Several generations can occur per year depending on storage conditions.
Damage & Detection
Packages or food items infested with these beetles usually have shot holes where adults have emerged from pupation. Adults and larvae cause damage. Adults are excellent fliers and are attracted to lights.
The use of pheromone traps and inspections can determine the location and degree of Drugstore Beetle infestation. These beetles are commonly found in processed foods such as spices, flour, meal, and dog food, but can also attack horn, wool, hair, pharmaceuticals and even book bindings. It is a common household pest.
Fun Facts about the Drugstore Beetle
Commonly confused with cigarette beetles (Lasioderma serricorne) and common furniture beetles (Anobium punctatum).
Other common names include biscuit beetle, bread beetle, library beetle, spice beetle, and bakery beetle.
Drugstore beetles initiate flight at temperatures above 20°C (68°F).
Drugstore beetles carry a symbiotic yeast that assists in digestion of less nutritious foods and can provide resistance to certain toxins.
The pheromone that attracts Drugstore beetles also attracts the common furniture beetle (Anobium punctatum).
Recommended monitoring systems & treatment for the Casemaking Clothes Moth:
- Hanging NoSurvivor Trap with PTL Multi-Species Bullet Lure (IL-408)
- Clothes Moth Bullet Lure
- Dragnet Dust
The use of pheromone traps for drugstore beetles can indicate their presence as well as where the beetles are coming from. The adult beetles are also highly attracted to insect light traps and can be monitored using these devices.
A visual inspection of dried food or spices in the vicinity of the pheromone traps or light traps containing the most beetles can reveal specific items containing larvae, pupae and adult beetles. Once an infestation is found, the infested materials should be sealed up and discarded or treated to kill the drugstore beetles.
Treatment options for drugstore beetles includes freezing for 1 week, such as with these insect freezer treatment bags, or having a certified pest management specialist perform an anoxic treatment on the infested materials.
