A reader wrote to us recently to ask “what kind of worm falls from the sky?” (The reader actually added three question marks, perhaps indicating his level of concern.) It turns out that the worms, which are small and white, aren’t actually falling from the sky, but rather from an oak tree (or so we surmise – more on this in a moment). The small white worms fall onto our reader’s car and truck, which are parked under an oak tree. The reader was first of all concerned with identifying what the small white worms on the oak tree are, but he was also keen to know where they are coming from. We address both concerns below.

The reader did not send a picture of the creatures he is finding, nor did he indicate where he lives, so we are working with incomplete information. Thus, any suggestion we come up with is tentative and subject to revision if more information becomes available.

When our reader made reference to worms on an oak tree, we immediately thought of cankerworms, which are the worms on silk threads that commonly infest oak trees. (For the record, cankerworms are a type of inchworm, which are not actually worms, but the larval form of geometer moths, making them caterpillars.) We also thought our reader might have found either tent caterpillars or gypsy moth caterpillars, both of which are caterpillars that infest oak trees. However, none of these creatures precisely matches the description of what our reader found. The reader’s small white worms are in fact extremely small (the reader said they are only 1/8 of an inch – or about 4 millimeters – long), and all of the caterpillars just mentioned are quite a bit larger. Moreover, none of these caterpillars are white. So, we don’t think our reader found cankerworms, tent caterpillars, or gypsy moth caterpillars, but we mention them because they are common oak tree pests. At the very least, other people searching for worms and oak trees might benefit from these suggestions.

With these three common oak tree “worms” out of contention, we investigated other possibilities, and found that our reader might be dealing with the larval form of a weevil. In particular, it sounds like he is dealing with one of the 30 or so species of weevil that belong to the genus Curculio. These creatures are often called “acorn weevils” because they infest oak trees. (Some species go after hickory trees, so the members of the genus Curculio are sometimes called “nut weevils” as well.) The larval forms of these weevils are very small and white; they essentially look like short, plump maggots. Adult weevils will lay eggs inside of acorns, and then the eggs hatch into the larvae, which bore holes to get out of the acorns once they have fallen off the trees. We suspect our reader is finding his small, white “worms” around this time in their development. If the weevil larvae didn’t end up on our reader’s car, they would have burrowed into the soil, where they would have matured for one to two years before becoming adults.

We are, again, not sure this is what our reader found, but we think there is a pretty good chance he is finding some type of weevil larvae. They are very small and white, which can’t be said of other creatures that infest oak trees. Thus, the small, white worms on the oak tree are in fact small, white larvae, or at least this seems like the most likely possibility.