Riding along the bigger rivers means that you occasionally encounter more lifeforms than you would otherwise. So far, I've seen a river snake (he escaped before I could take a photo), the preying mantis, and now this little guy. He was trying to cross the bike path (why? to get to the Starbucks on the other side) and doing a pretty good job of it. About 3" long. Interesting camouflage as well - the horn at the bigger end actually represents the tail. The mouth is on the small, tapered end. In Japanese, this is an imomushi (芋虫), but I can't find a specific species name for it.
This part of the bike trail is about 4 miles from the Takao foothills, which I visited the same day as part of a trip up to look at the ruins of Hachioji castle. On the ruins grounds in the hillside forest, there are signs warning against encountering monkeys and mamushi (Japanese pit vipers). I'm hoping I can find a mamushi next time.