Long, White Worms

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Some time ago, we received a question from a reader about long, white worms he has been finding in his back yard. He has found the worms on multiple occasions, and he was wondering what kind of creature he might be coming across. In addition to being long, they are evidently quite thick as well, as the reader describes the white worms as being “as big around as a finger.” What are these long, white worms in the back yard? Are they worms at all, or are they another type of creature, perhaps a caterpillar or some other type of larva? Let’s find out.

Or perhaps not. Unfortunately, virtually every part of our reader’s question is imprecise. First, are the worms literally white, or are they an off-white color, perhaps a cream, tan, or yellow hue? Rare is the creature in nature that is pure white, so there is a reasonably good chance he did mean off-white, but that is all we know. The reader also described the worm as “really long,” but what does that mean exactly? One person’s “really long” is not another’s. The one fairly specific thing the reader did say about the creature he found is that its circumference is comparable to that of a finger’s. If the creature ought to be regarded as very long even relative to its thickness (and this seems to be the way people employ the dimension of length – you wouldn’t describe an insect the shape of a basketball as long, even if were actually the size of a basketball), then the creature our reader found seems huge by worm standards. It sounds more like a snake than a worm, and for all we know it is. We also don’t know where our reader lives, nor do we know if the creature in question has any distinctive characteristics (e.g., lots of legs, which would suggest that our reader found a centipede or millipede – there are white species of both).

Given our radical uncertainty, no answer we can muster should be regarded as even in the galaxy of definitive. We simple know too little. However, as we’ve said before, we have a nearly pathological drive to answer reader questions, so here goes…

One type of worm that can be both long and white are ascarids, which are sometimes merely called roundworms (not to be confused with the entire Phylum Nematoda, the members of which are also loosely referred to as “roundworms”). Ascarids primarily afflict young dogs and cats by stunting development and causing intestinal pain. The problem with this theory is that ascarids are inside the body, and if they are ever found outside dogs or cats, they are surrounded by the vomit or feces of the infected animal. Even with our reader’s penchant for brevity, it seems unlikely that he wouldn’t mention such a glaringly relevant fact. Tapeworms can also be long and white, but this suggestion is as unlikely as that of ascarids for similar reasons: they live in the digestive tract of afflicted animals, and if they are ever observed outside of the body, they are in segments (i.e., the full worm isn’t observed) and embedded in feces.

There are also several white caterpillars in the world, and perhaps our reader found one of these. We know of none that fit the dimensions implied by our reader, but it’s certainly possible he mistook a caterpillar for a worm. Indeed, this happens all the time, much like readers mistake insect larvae (e.g., maggots) for worms. (Speaking of larvae, we can be all but sure our reader didn’t find the larval form of any type of insect – the creature he saw seems far too large.)

So, we will conclude this article the way we started it: with uncertainty. We’d love nothing more than to supply an indubitable answer to our reader’s question, but unfortunately we just don’t know what kind of long, white worm he might have found. For one, we weren’t given much information about the creature, and two, we don’t know of any huge white worms one might find in their back yard anyway. If any readers have suggestions, please leave a comment.


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