A reader recently asked what the black worms in his or her bed might be (others have asked the same question with regard to their pet’s bed). Unfortunately, the size of the worms wasn’t specified, but if they were really small, the likely answer is that they are actually flea larvae.

Fleas are of course those small, annoying insects that bite and suck blood from their host. Commonly, the host is a cat or dog, although humans can be affected by fleas too. Fleas cause itching, which is bothersome enough, but they can also carry dangerous parasites, so it’s important to terminate any fleas that you find on yourself and your pets, or in an area near yourself or your pets.

The flea life cycle is broken into four stages: the egg stage, larva stage, pupa stage, and, finally, adulthood. In any given flea population, the majority will be in the egg state (about 50%), but another 35% will be in the larva stage. 10% of the population is in the pupa stage, and the remaining 5% are adults.

It is in the larva stage that one is most likely to mistake a developing flea for a type of worm. Flea larvae certainly look like tiny worms, and they can come in a few different colors (not just black, as the reader’s question specified). Most tend to pale, although many have a dark, blackish interior that can be seen, meaning that they can, indeed, look like small, black worms.

How might flea larvae make it onto your sheets? Overwhelmingly, the answer is your pets, as dogs and cats get fleas more frequently than humans. If you allow your pets to sleep on your bed or even just occasionally invite them up, they might spread flea larvae to your bedding. Very often, flea larvae is observed on pet bedding – in fact, that is one of the ways owners can check to see if their pets have fleas – so it stands to reason that flea larvae can be found anywhere that your pet lies down.

So, if you find “black worms” in your bed, you might be dealing with flea larvae, and you should take the necessary steps to eradicate fleas from your pet and your home.