We received an interesting, if somewhat vague, question from a reader about a brown worm he found in the garden. The worm was described as not only “brown,” but also “fat.” The fat, brown worm is about two inches (five centimeters) long, and its body dimensions resemble that of the “tomato hook worm,” by which we are fairly sure our reader meant “tomato hornworm,” the larval form of a moth (Manduca sexta), making the tomato hornworm a caterpillar. Speaking of caterpillars, it is possible our reader found a fat, brown caterpillar, as opposed to a fat, brown worm, so that is something to keep in mind as we consider some possibilities for what our reader might have found in this garden.

Alas, our reader submitted no picture along with his question, so we can’t check our research against the phenotype of the creature our reader found. Our attempts at an answer are therefore more speculative than usual, but we suppose any educated guesses are better than none.

Let us start with perhaps the most obvious suggestion: maybe our reader found a common earthworm, one of the many types of worms in the subclass Oligochaeta. (There are actually many species of earthworms, but they are similar, so we’ll treat the various earthworms as one possible answer to our reader’s question.) Your standard earthworm is generally brown, just as our reader’s creature is, and they could also be construed as fat depending on one’s conception of a fat worm. They are often described as “plump,” and hence their popularity as fish bait. Earthworms vary widely in length – some are only a couple of inches long, whereas others can be nearly a foot in length. Again, this is consistent with what our reader found, although he evidently found a shorter one. Finally, it is far from strange to find an earthworm in a garden. They live in moist soil, which gardens are known to have. (As a relevant side note, earthworms are wonderful for your garden, as they aerate soil, which helps plants grow. We figured we’d mention this in case our reader regarded her worm as a “pest” – it could be, but not if it is an earthworm.)

If our reader found a worm, our best guess is that he found an earthworm, and in the absence of other evidence, we are inclined to think that he did in fact find a worm. As we mentioned above, it is possible he found a caterpillar, but we haven’t been able to find any caterpillars that are generally found in gardens that match our reader’s description. Black soldier fly larvae (BSFL), which aren’t caterpillars, are indeed fat and brown, but they are a lot shorter than two inches long (they are more like a quarter of inch in length most of the time), and they are generally found in compost heaps or their natural counterpart (heaps of rotting organic matter), not gardens.

Rather than a worm or a caterpillar, it is possible that our reader found a millipede. This would be somewhat surprising because most people who find millipedes immediately point out their most notable feature – all of their legs – but if the reader didn’t get a good look at the creature he found, he might not have seen the legs. (Millipede legs, in contrast to centipede legs, do not extend from the body.) Moreover, millipedes are commonly found in gardens, and it would not be peculiar to find a fat and brown one. We recommend our reader search for “garden millipede” to see if any creature comes up that matches the one she found. Several images of what appear to be fat, brown “worms” will immediately come up.

We aren’t sure what the fat, brown worm in the garden our reader found is, but we have at least offered a couple of possibilities – namely, earthworms or some type of millipede – that can be investigated further.

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