Grain Beetles
Grain beetles are small, flat, brown beetles that infest a wide range of stored food products. The sawtoothed grain beetle and merchant grain beetle are the most common species. Their extremely flat body shape allows them to penetrate sealed packaging through tiny gaps and folds. They feed on flour, cereal, dried fruit, chocolate, sugar, nuts, and many other processed foods. They are among the most common pantry pests encountered in homes and are frequently the first insect noticed when a pantry infestation begins.
Species in This Group (2)
Sawtoothed Grain Beetle
Oryzaephilus surinamensis
The Sawtoothed Grain Beetle is a common pantry pest that infests processed grain products.
Merchant Grain Beetle
Oryzaephilus mercator
The Merchant Grain Beetle is nearly identical to the Sawtoothed Grain Beetle in appearance but differs in food preferences, favoring oily products like nuts, seeds, chocolate, and dried fruit over plain cereals.
Key Behaviors
Grain beetles exploit their extremely flat body profile to enter packaging through seams, folds, and tiny gaps. They cannot attack whole, undamaged grain but thrive on processed products. They are strong crawlers and readily spread from infested products to adjacent items on shelves. Populations develop rapidly in warm conditions with generation times as short as 27 days. The merchant grain beetle can fly while the sawtoothed grain beetle cannot.
Risks & Concerns
Grain beetles contaminate stored food products with their bodies, frass, and shed skins. Their ability to penetrate packaging makes them particularly difficult to exclude. Infestations spread readily through pantries and can involve multiple products simultaneously. In commercial food storage and processing, they are a persistent quality control issue requiring integrated pest management approaches.
Quick Comparison
| Species | Size | Color | Key Trait |
|---|---|---|---|
| Sawtoothed Grain Beetle | 2.5-3 mm | Flat, dark brown | Very flat body with six saw-tooth projections on each side of the thorax; infests processed grain products. |
| Merchant Grain Beetle | 2.5-3 mm | Flat, dark brown - nearly identical to sawtoothed grain beetle | Nearly identical to sawtoothed grain beetle but prefers oilier products like nuts, chocolate, and dried fruit. |
Need Help With Grain beetles?
If you're seeing signs of grain beetles in or around your home, professional treatment is the fastest way to stop the problem. Lotus Pest Control offers free inspections to identify the issue and recommend the right solution.