Few things are more startling than turning on a basement light and seeing a strange, many-legged creature suddenly race across the floor. If you’ve experienced this, there’s a good chance you encountered a house centipede. Its long body, numerous legs, and incredible speed can make it look frightening, but this unusual visitor is generally far less dangerous than it appears. In fact, it may be helping your home by hunting other unwanted pests.

House centipedes prefer dark, cool, and damp areas such as basements, bathrooms, garages, laundry rooms, and spaces under sinks. An adult can have up to 15 pairs of legs, with the legs becoming longer toward the back. Their speed is one of their most noticeable features, allowing them to quickly chase prey or escape danger. “Their speed isn’t intended to frighten humans. It’s part of how they survive.”

For most people, house centipedes are not dangerous. They usually avoid humans, and bites are uncommon. More importantly, they are predators that feed on spiders, ants, cockroaches, silverfish, termites, flies, and other small household creatures. That means the terrifying insect running across your floor may actually be providing a form of natural pest control.

Seeing one can also reveal something about your home. House centipedes are attracted to moisture and places where other insects are available as food. Leaking pipes, damp foundations, condensation, or poor ventilation can create ideal conditions for them. If you are seeing them often, reducing moisture, fixing leaks, improving ventilation, sealing cracks, and dealing with other pests may help.

The next time one suddenly races across your basement, try not to panic. “It’s looking for bugs.” You certainly don’t have to welcome a fifteen-legged visitor into your home, but understanding its role may make the sight a little less frightening. Sometimes the creature that looks like the worst thing in your house is actually helping take care of something worse.