Every summer I am shocked, simply shocked by the wanton hedonism that transpires in my tomato garden. Sometimes, I have seen several pairs of earthworms mating simultaneously. Last night was the first pair that I’ve noticed so far this year, so I guess the “season” has begun. When you think about it, earthworms are probably the largest animals that most of us are likely to observe in the act of mating — at least, on a regular basis.
A good source for earthworm information is Earthworm Watch. There are a variety of sources for earthworm facts & trivia online — here’s one with a high density of information, and another with some surprising information about their ecology. You may also be interested in earthworm toilets, which were in the news just a few months back (those are toilets for people, not for the earthworms).