Imagine my surprise and delight yesterday morning when, while looking for slugs, I instead came upon a Bipalium adventitium crawling about on the wet trunk of a beech.
This was near the spot where I had found another one of these land planarians in May 2009. Obviously, these planarians, which are believed to have been introduced to North America from eastern Asia, have established themselves in the wild and are here to stay.
After taking a few pictures of the planarian, I put it in a container and brought it home. This morning I put it and the one I've been keeping since last September in a wet petri dish. The planarians in the genus Bipalium are known to mate1, that is reproduce sexually, and then produce cocoons containing offspring. However, not much seems to have been published about their reproductive biology. So I was hoping to gain some carnal knowledge from these slimy beasts.
After almost 12 hours of confinement and numerous encounters, I don't think the 2 have mated yet. One problem is I don't quite know how I can tell when 2 planarians are mating. And how long does their mating last? There were several occasions when the 2 were on top of each other, but I didn't notice anything unusual that would have indicated they were copulating.
But at least they seemed to be enjoying each other's company, if they have such feelings.
Observations will continue and updates may be posted.
1Ogren & Sheldon. 1991. Ecological observations on the land planarian Bipalium pennsylvanicum...Proc. Penn. Acad. Sci. 65:3-9.