17 November 2008

Slugs on the beech

The native philomycid slug Megapallifera mutabilis, abundant in the woods near my house, has a thing for beech trees. In this post I noted how one can tell that there are philomycid slugs at a location from the feeding tracks they leave on the algae-covered smooth trunks of beech trees (Fagus grandifolia).

This past weekend's weather, wet and unseasonably warm, was good for slugs. During a walk in the woods I came upon this beech, still wet from the earlier rain, with many shiny lines covering its trunk. Some of them may have been the trails left by streams of water running down to the ground, but at least those that were going sideways were definitely slug trails.


In fact, there were 2 slugs on it (arrows). The higher and the bigger one was about 4 m above the ground. To ascertain that it was what I thought it was, I brought it down with a long stick.


It was what indeed a Megapallifera mutabilis. The fall didn't harm it and after it untwisted itself, it went about its business.



Megan said...

Judging by their tracks and choices of rest spots, the Megapallifera seem to like those wet patches on the tree trunk! Do you suppose that moistened algae is easier to chew than dry?


Yes, the wet algae is probably easier to scrape off. And also when the slugs are on a wet patch, they must lose less water.

George said...

Wet algae might be more biologically active than dry, and so contain more nourishment