We’ve had a huge snowmelt, and yesterday we got a fair amount of rain. The ground is a soupy, muddy mush, and an an inevitable result we’ve seen the worms come out. On this morning’s walk they were coating the driveway, causing me to tiptoe through them to avoid unnecessary worm-flattening. (I admit that doing that is a bit silly, because when I back my car out of the garage in an hour or so I will pulverize many of them — but I least I won’t feel like I could have avoided it.)
Why do worms appear in wet weather? The conventional story is that they drown underground in such conditions, but that turns our to be incorrect. According to various “we answer weird questions” websites, worms come out when it is wet because the surface finally is favorable for them. Worms are covered in mucus that facilitates their approach to breathing. If they come up when it is hot and dry, the mucus dries out and the worms then becme dessicated and die. That is not a problem when the weather is wet. See here and here.
It turns out that there is another crucial reason: sex. Worms like to mate above ground. Because all worms tend to come above ground when it is wet, the surface is fertile territory (pun intended) for finding a worm willing to exchange bodily fluids and propagate the species. It is like a giant, free-for-all worm speed-dating opportunity. The space above ground also helps the worms attain a comfortable “mating posture,” which probably would be interesting to learn more about because worms are simultaneous hermaphrodites, with each mate exchanging sperm.
So we should all be careful walking after a rain, so as not to disturb a worm’s moment of romance under the stars.