Frequently asked questions about earthworms and vermicomposting

We often get all sorts of little questions about earthworms, some very serious, some a bit more unusual — do they have eyes, how long do they live, can they swim? We've gathered the most frequent and most curious ones here, along with their answers, collected over the course of our conversations with our customers.

The body and senses of composting worms

Do earthworms have eyes?

No, worms have no eyes, but their skin is covered in light-sensitive cells, concentrated mainly at the front of their body. These allow them to detect changes in light intensity and to sense vibrations in the soil — more than enough to flee from light and disturbances without ever really "seeing."

How do composting worms breathe?

Worms have no lungs: they breathe directly through their skin, which must stay coated in mucus and moisture so that oxygen can dissolve through to their bloodstream. That's why bedding that's too dry puts them in danger much faster than occasional excess moisture.

Do earthworms have teeth?

No, neither teeth nor jaws: their mouth and pharynx are muscular but completely toothless. They can only swallow particles that are already fairly small and softened by moisture and bacteria. A muscular gizzard, further along their digestive system, finishes the job by grinding the food with the tiny grains of soil it contains — a bit like in birds.

Does an earthworm have a heart?

Even better: it has several! A composting worm has several blood vessels that act as little hearts to pump its blood around. Another curiosity: it never sleeps and stays active around the clock, as long as conditions suit it.

Can you cut a worm in half to get two?

No, this is a popular myth that doesn't work and only needlessly injures the animal. Worms' ability to regenerate is real but limited: the front part can sometimes regrow a new tail, but the back part can never form a new head. Rest assured: in good conditions, a single worm can produce several hundred offspring without you ever needing to touch it!

Reproduction and life cycle

How do earthworms reproduce?

In short: worms are hermaphrodites, but they still need to mate in order to reproduce, belly to belly and head to tail. We explain the whole process, cocoons included, in our guide Earthworm reproduction.

How can you recognize composting worm cocoons?

A cocoon measures about 0.12 in (3 mm), roughly the size of a grain of rice. Pearly white at first, it gradually changes color as the young worms develop inside, turning brown and then reddish just before hatching, about three weeks later.

How long does an earthworm live?

You may have noticed different figures across our guides, so here's the chance to clear them up. In the wild, most worms live and die within a single year, facing cold, drought, or predators. In a well-maintained worm composter, sheltered from these dangers, their life expectancy rises considerably: individual Eisenia fetida have been tracked in captivity for up to 4.5 years. It's this potential, achievable in good conditions, that we use as our reference (4 to 5 years) throughout the rest of this guide.

How many species of earthworm are there?

Around 4,400 species of earthworm have been recorded worldwide to date! But only a few, such as the Eisenia we raise, are truly suited to vermicomposting — most other species wouldn't survive the conditions in a worm bin.

Did you know?

Can earthworms swim?

Not really, no — but that isn't necessarily a problem: as long as the water stays well oxygenated, a worm can survive underwater for quite a while without drowning. What's really fatal to them is too much stagnant, oxygen-poor water, rather than water itself.

Does noise bother composting worms?

A little, yes: worms aren't exactly party animals, and noise and vibrations disturb them somewhat. The good news is that they adapt pretty well over time, even to a noisy environment.

Why are some earthworms nicknamed "rainworms"?

That's the case with Lumbricus terrestris, the large burrowing worm we come across in our yards (different from the Eisenia composting worms used in a worm composter): it comes up to the surface as soon as the soil gets damp, in spring or on rainy fall nights — hence its nickname.

How much food can a worm eat per day?

Expect the equivalent of half its own body weight per day on average, sometimes up to its entire body weight in good conditions. For 1.1 lb (500 g) of worms, for example, that comes to around 8.8 oz (250 g) of food scraps digested every day — our guide The earthworm diet details everything you can (or can't) feed them.

In summary

With no eyes or teeth, several hearts, and no ability to swim, earthworms have plenty of surprising features — as does their life expectancy, which varies greatly between the wild and a well-maintained worm composter. Don't see your question here? Feel free to ask us directly.

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