I wrote about the land planarian Bipalium adventitium in this post. That individual ended up in a vial of alcohol soon after that post was written. Last Friday, I found another one under a log in a park. There were also earthworms in the soil under the same log; they are the planarian's main, if not the sole, prey.
Here is a picture I took in the field; the planarian was still on the underside of the log.
It's hard to give dimensions for these animals, because their bodies are very stretchable. In this picture, the planarian was probably ~4 cm long.
I have also taken several video clips of it while it was crawling on a glass plate. Here is one of them. Excuse the quality; this is the best I can do with my current camera.
Notice how it moves its head from side to side as it crawls. That's the characteristic behavior of these planarians. The lateral movements of the head presumably enable the sensors on the head to pick up chemical clues from the environment.
The planarian hasn't eaten for at least about 50 hours. I have selected an unfortunate earthworm from the backyard and will be giving it to the planarian soon.
More will be in Part 3.