What do Worms Eat? What do Worms Not Eat?

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The other day, a reader asked us one very simple question: “what do worms eat?” Unlike some simple questions we receive, this one is actually pretty straightforward. Worms eat a variety of things, which we will detail below. What worms do not eat is also notable, so we will touch on this topic too. Thus, we will write about two separate, but obviously closely related, questions: What do worms eat? What do worms not eat?

First, we should note, as we always must, that the word “worm” is used in a particularly loose way. It is barely an exaggeration to say that anything cylindrically shaped is called a “worm.” However, even if you adopt a narrower rule of usage, as we do, there are still tens of thousands of worm species. So, the question “what do worms eat?” is more expansive than our reader might have realized. To keep the focus on this article within reason, however, we’ll focus on earthworms. When most people think of worms or use the word “worm,” they probably have earthworms in mind.

However, even limiting ourselves to earthworms is problematic, as there are thousands of species of earthworms as well. There are epigeic, endogeic, and anecic earthworms, classifications which concern how they behave in soil and thus what they eat. Endogeic worms, for instance, rarely come to the surface, so while they do eat decaying organic matter, as all earthworms do, they also eat soil itself. Technically, all earthworms end up eating some soil, but they do so incidentally in the course of eating dead organic matter. Endogeic worms actually derive minerals from the soil. As you can see, things can quickly get technical and detail-laden in the world of worms, but there is no reason to dwell on fine shades of difference between different types of earthworms. Basically, earthworms eat dead organic matter, and it is really as simply as that.

By dead or decaying organic matter, we mean things like dead grass and leaf litter, as well as related materials from plants that have died. They also eat dead animals, helping with the decomposition process. In eating these items, they also ingest a lot of bacteria and fungi, rounding out their diet. As you might have noticed, we are describing the fundamental things found in compost bins – basically, vegetables and meats – which is why worms are such an integral part of composting operations. Any earthworm could in some sense be a part of a composting bin – the ground and the soil beneath it are basically one enormous composting bin – but only epigeic worms are enlisted by people for their composting needs. The types and range of things thrown in compost bins are handled most efficiently by epigeic worms, such as Eisenia fetida, or red wigglers. Epigeic worms don’t make elaborate tunnels like endogeic and anecic worms, and they can quickly adjust to the changing environment they are in. (The composition of compost bins obviously changes quickly.)

We’ll conclude by rounding out the topic in the way promised above – by addressing what worms do not eat. Obviously, they don’t eat any number of random things – like metal, plastic, or similar items that you wouldn’t expect them to eat – but what we want to call attention to is the fact that they don’t eat living organic matter. (Hence the use of “dead” or “decaying” when we described their diets.) So, earthworms are never a threat to your lawn or garden, and in fact only help your plants grow by aerating dirt with their tunnels and enriching it with their frass. Thus, worms eat all sort of things, but not the things you wouldn’t want them to.


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What do Worms Eat? What do Worms Not Eat?
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What do Worms Eat? What do Worms Not Eat?
Answers to two separate, but obviously closely related, questions: What do worms eat? What do worms not eat?

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