Shiny Spider Beetles

Facts, Identification & Control

Latin Name

Mezium affine


The shiny spider beetle (Mezium affine) is a pest of stored food products. It gets its name from the fact that the adult beetle resembles a small spider. The wing covers give it a “humped” appearance. It is a small insect. Adults range in size from 1.5 to 3.5 mm.

The shiny spider beetle is solid colored. The color varies from dark red to black.

Behavior, Diet & Habits

This beetle is often confused with the American spider beetle, which has cream-colored head and legs. There are several other species of spider beetles, including the Australian, the golden and the whitemarked.

The shiny spider beetle feeds on moldy food and food products. It also feeds on products that have been stored a very long time and are out of condition for use by people. Shiny spider beetles have infested houses, hotels, warehouses and bakeries. They feed on cereal, pet food, stored seeds, woolens, animal droppings and paper.

Shiny spider beetles have also been found in bird nests and rat nests. When the nests are in attics or crawl spaces, the beetles can easily move into the living space.


The female beetle deposits eggs on the food material. When the eggs hatch, the larvae feed and grow. While they are feeding, the larvae spin silken webbing.  When they are ready to change into adult beetles, the larvae spin silken cocoons. The adults sometimes stay in the cocoons for a few days before coming out to find a mate.

The length of time for development depends on the temperature and the amount of food that is available.

Signs of a Shiny Spider Beetle Infestation

The adult beetles and holes in packaging can indicate activity. Inside packaging, some webbing might be observed.

More Information

Shiny spider beetles ruin more food with their webbing and their droppings than they actually eat. Webbing on food and holes in packages is a sign that shiny spider beetles may be active.

Inspection and cleaning are the key steps in eliminating shiny spider beetles. It is important to find everything that they have infested. Empty pantry and cabinet shelves. Inspect every package and throw away any that are infested. Vacuum the empty shelves. This will remove any food residue. Store new food products in sealed glass or plastic containers.

Insecticide application is the final step. Apply it into the cracks and crevices at the back and sides of the shelves. Treat cracks and crevices in any other areas where the beetles have been active. The object is to eliminate any insects that might be hiding. To avoid misapplication, it is often preferable to call the local pest control professional.