North American Millipede: Harmless but Startlingly Large

Identifying Those 5-Inch "Worms" in Your Home

If you're finding large, cylindrical, many-legged creatures (up to 5 inches) in and around your house, you're seeing the North American millipede (Narceus americanus). Despite their alarming size, they're completely harmless—no bite, no sting, no damage to structures.

Common Millipede Species in the Region

• North American millipede (Narceus americanus): Large, dark brown/black, up to 5+"
• Garden millipede (Oxidus gracilis): Small (1"), flattened, often in huge numbers
• Giant African millipede (Archispirostreptus gigas): Pet trade escapee, not established outdoors

Why They Enter Homes

Millipedes migrate en masse after heavy rains saturate soil or during drought seeking moisture. They enter through gaps under doors, foundation cracks, and vents. They die quickly indoors from desiccation.

Management

• Seal entry points (door sweeps, caulk, screen vents)
• Reduce mulch depth near foundation (2–3" max)
• Divert downspouts and irrigation away from foundation
• Perimeter treatment with labeled insecticide if migrations are severe
• Vacuum or sweep up indoor specimens