How to Inspect Stored Grains for Spider Beetles?

How to Check for Spider Beetles in Stored Grains?

Spider beetles are small and good at hiding. Use the following methods to accurately determine if your grains are infested:

Visual Inspection

1. Pour a small amount of grain onto a light-colored tray or white paper and spread it out
2. Examine carefully under good light — look for small, roundish beetles moving slowly
3. Spider beetles play dead when startled, so observe patiently for at least 30 seconds
4. Check grain surfaces for pinhole-sized bore holes

Sifting Method

• Sift the grain through a fine sieve (about 1 mm mesh)
• Adult and larval spider beetles will be sifted out
• The sifted debris will show droppings, shed skins, and powder
• This is the most effective method for checking fine grains like flour and rice flour

Check Storage Cabinets

• Open cabinets and check corners for fine powder
• Look between shelf panels for shed skins (cast skins from molting larvae)
• Look for small, spider-like beetles crawling on cabinet walls
• Check package seals and folded corners for eggs or larvae

Smell Check

• Grains heavily infested with spider beetles will have a musty or off odor
• This comes from insect droppings and shed skins mixed into the grain
• If you smell anything off, the infestation is already quite serious