The small black worms you’re finding in your house are almost certainly the larvae of an insect, not actual worms. The most common culprits are drain fly larvae (especially in bathrooms and kitchens), carpet beetle larvae (near fabrics, carpets, or stored food), and millipedes (which wander in from outdoors through damp entry points). Where you found them is the biggest clue to figuring out which one you’re dealing with.
Black Worms Near Drains or Showers
If the dark, squirming creatures showed up around your shower drain, bathtub, sink, or on grout lines, they’re almost certainly drain fly larvae. These are technically not worms at all. They’re the immature stage of tiny flies that breed inside the slimy organic film that builds up in pipes. The larvae are slender, roughly a quarter inch or less, and range from creamy brown to dark gray or black. They have a distinct head and a segmented body made up of 11 sections.
Drain flies lay their eggs directly in the gunk that lines your pipes, where soap residue, hair, skin cells, and moisture create a perfect food source. Once eggs hatch, larvae feed on that film for 9 to 15 days at typical room temperature, completing their full life cycle in about 21 to 27 days. At warmer temperatures (around 85°F), the cycle speeds up. That’s why infestations often seem to appear suddenly and grow quickly in warm, humid months.
Every drain in your home is a potential breeding site: sink drains, toilets, floor drains, tub drains, and leaky shower pans. If you suspect a particular drain, place a clear glass or plastic cup coated inside with petroleum jelly over it overnight. Any adult flies emerging from the drain will get trapped, confirming that’s where the larvae are coming from.
How to Get Rid of Drain Fly Larvae
No insecticide is registered for use inside drains or sewer systems, so pouring bleach or pesticide down the drain isn’t the right approach. The goal is to physically remove the organic buildup the larvae feed on. Without food, the life cycle breaks and no new flies emerge.
Start by scrubbing the inside of the pipe with a stiff metal pipe brush, pushing it back and forth as far as it reaches. Follow that with boiling water poured slowly down the drain. Repeat daily for about a week. For a deeper clean, pour half a cup of salt, half a cup of baking soda, and one cup of vinegar down the drain before bed, then flush with boiling water in the morning. Enzymatic or biological drain cleaners that break down organic matter also work well and are nontoxic. Foaming drain products can reach buildup that liquid cleaners miss.
Check every drain in the area, not just the one where you spotted larvae. Populations often breed in multiple drains at once, and missing one will keep the problem going. If the infestation keeps returning despite thorough cleaning of all drains, that can signal a broken pipe or a leak beneath a slab or crawlspace, where organic matter accumulates out of sight.
Black Worms Near Carpets, Closets, or Pantries
If you’re finding small dark larvae near rugs, along baseboards, inside closets, or in stored food, carpet beetle larvae are the likely suspect. The black carpet beetle larva grows up to about 5/16 of an inch, ranges from light brown to nearly black, and has a shiny, smooth body covered in short stiff hairs. It tapers toward the rear and ends in a tuft of longer hairs. Other carpet beetle species have fuzzy, striped larvae that look more like tiny hairy caterpillars.
Carpet beetle larvae feed on animal-based materials: wool, leather, silk, feathers, fur, and dried animal products. They don’t eat synthetic fibers. In drier climates, the black carpet beetle is actually more of a pantry pest, going after grains, flour, and cereals. You can identify their presence by the tiny brown, bristly cast skins they leave behind when they molt, along with fecal pellets about the size of a grain of salt. Unlike clothes moths, carpet beetle larvae don’t produce webbing, and they tend to damage one concentrated area of fabric rather than leaving scattered holes.
To deal with carpet beetles, vacuum thoroughly along baseboards, under furniture, and inside closets, paying special attention to areas where pet hair, lint, or food crumbs collect. Wash or dry-clean affected fabrics. Store wool and silk items in sealed containers. Inspect dried food products in your pantry and discard anything infested.
Millipedes and Other Possibilities
If what you found is longer (an inch or more), moves slowly, and curls into a spiral when disturbed, it’s likely a millipede. Millipedes are not insects. They’re arthropods with dozens of legs, though at a quick glance they look like shiny black or brown worms. They live outdoors in leaf litter and moist soil, and typically wander inside during heavy rain, drought, or when outdoor conditions push them toward the foundation of your home.
Millipedes can’t survive long indoors because they need constant moisture. Finding one or two is normal and doesn’t indicate an infestation. Reducing moisture around your foundation, sealing gaps around doors and windows, and clearing mulch or leaf debris from the perimeter of your house will keep them from coming in.
Figuring Out What You Have
Location is the fastest way to narrow it down:
- Bathroom, kitchen, or near any drain: drain fly larvae. Small, dark, segmented, found in or near standing water or damp grout.
- Closets, carpets, baseboards, or pantry: carpet beetle larvae. Look for shed skins and damage to wool, silk, or stored food.
- Entryways, basements, or garage: millipedes. Longer, many-legged, curl into a coil when touched.
In all three cases, moisture and organic material are what draw them in. Fixing leaks, improving ventilation in damp rooms, keeping drains clean, and storing fabrics and dry goods in sealed containers addresses the root cause for virtually every type of “black worm” that shows up indoors.