After several days with temperatures just above the freezing and even colder nights, the weather got slightly milder over the weekend and it rained. So this morning I decided to do one more search for slugs in the woods before the cold weather returned.
A half an hour spent staring at wet beech trunks yielded 2 Megapallifera mutabilis. Here is one of them.
The air temperature near the slug, as seen in the photo, was 5.6°C. This slug was colder than these, but not as cold as this one.