My daughter found a very strange bug that looks like it is full of blood. I thought it was a bed bug and took it to the University where they said it was a spider beetle. Doesn’t look like a spider to me. What’s it doing in my house? W. P., Melrose, MA

Spider beetle, Gibbium psylloides

Spider beetles are not very common in homes. They are more often pests in food warehouses or in flour and grain mills. They are considered to be minor pests of stored grains because they develop slowly and, like many stored food pests, infest foods that are already old, moldy, or damaged. In homes, grains or dry pet food or birdseed that is stored in bulk can be infested. Spices and dried foods such as dried meat, dried fruit, dried mushrooms, nuts, and beans can also be the source of a spider beetle infestation in a kitchen. And sometimes, the infestation can be tracked to food or rodent bait that mice have hidden in wall voids.

Spider Beetles Are General Scavengers in Homes

Besides being occasional food pests, spider beetles are also scavengers on a variety of plant and animal materials and can become pests in museums. They are found infesting strange sites and items such as animal hair, feathers, bird or rodent nests, pet poop, rodent droppings, dead insects, even dead mice or other animals. So, without an inspection, it would be impossible to tell where your beetle developed or even whether there are more of them in your home. Spider beetles like cool temperatures and are more common as pests in northern regions. They’re active mostly at night.

There are lots of different spider beetles with very different appearances. Many of them have rounded bodies with long legs which is where they get the name. Some spider beetles are rather hairy while other have bulbous, shiny, blood-red bodies. You are probably talking about Gibbium psylloides, also called the “hump beetle” which is only about 1/10-inch long. Rest assured that it does not bite people or suck blood. But you’re not alone, people often mistake this beetle for an engorged blood-sucking tick. Spider beetle larvae are C-shaped and look like miniature grubs. They camouflage themselves with silk and bits of the food product.

If you can find the source of the spider beetle infestation in a home, it is usually easily eliminated by simply discarding the infested item(s). If you see more of these beetles, you should contact an exterminator who can conduct a professional inspection.

Photo Credit : “Gibbium psylloides” | CC BY-SA 3.0 via Wikimedia Commons.