American Spider Beetles

Facts, Identification and Control

Latin Name

Mezium americanum (Laporte)

Appearance

What Do They Look Like?

  • Appendages: American spider beetles have long legs and antennae.
  • Body & Head: Its head and thorax are covered with small hairs. The beetle’s name comes from the shape of the adult beetle, which has a “humped” appearance. When viewed from above, it resembles a spider.
  • Color: The adult American spider beetle is a shiny, reddish brown to almost black. The head and legs are cream colored. Larvae are curved and whitish in color.

Similar Species
American spider beetles are often confused with the shiny spider beetle, which is completely reddish brown. There are several other species of spider beetles, including:

How Did I Get American Spider Beetles?

American spider beetles lay their eggs in stored food items like grains and flour. Infestations usually begin when homeowners buy goods already tainted by the pests. Animal waste, feathers, and nests may also attract these insects.

How Serious Are American Spider Beetles?

American spider beetles are not a threat to human health, but are scavenger pests of stored food. They become nuisances when they chew holes in packaging, leave behind webbing and cocoons in food, and damage fabrics.

Associated Problems
Their presence can also indicate other pest issues. Rodent nests and bat droppings are common American spider beetle habitats. Since the insects forage during the evenings and hide in dark spaces, they can be elusive and tough to spot.

How Do I Get Rid of American Spider Beetles?

What You Can Do
Follow these strategies to help with American beetle control and prevention:

  • Clean up – Throw away all infested food.
  • Vacuum – Vacuum pantry and cabinet shelves thoroughly. This will remove any food residue that larvae might eat. Vacuuming will also remove any beetles that are still in their cocoons.
  • Practice good food storage habits – Store new food products in sealed containers.

What Orkin Does
Controlling spider beetles in homes starts with a thorough inspection. Insecticide will be most effective if it is applied into cracks and crevices or voids. For product selection and application, it is usually best to contact your pest control professional.


Signs of an American Spider Beetle Infestation

Some signs of infestation are:

  • Holes in packages
  • Webbing in food
  • Silken cocoons

Infested boxes or packages will have small 1 to 2 mm size holes. Round silk cocoons that appear are about 4 mm in size.

Behavior, Diet & Habits

Where Do They Live?
Since they can live by scavenging, American spider beetles can survive in places like empty warehouses. They are attracted to moist, damp areas and can become pests in mills, food processing facilities, and museums. The adult beetles are usually active at night or in dark places, so they are difficult to see.

Spider beetles can infest bird and rodent nests. If the nest happens to be in the attic or crawl space of a home, the beetles can easily move into the living space.

What Do They Eat?
American spider beetles eat products that are moldy or products that have been stored too long to be usable.

Larvae Diet
Adult spider beetles deposit their eggs in the material that the larvae will eat after they hatch. This may be broken grain or flour and grain products. They also feed on hairs, feathers, and even waste from birds or mammals like old rodent droppings and other debris depending on location.