Garbage Worm

Garbage Worms are creatures made up of a single, flexible black tendril ending in a bulb very similar to an eye-stalk. They are generally found sprouting from dirty water or garbage, especially from the Garbage Wastes region, they are neutral by nature and won't attack until provoked, this includes Slugcat and lizards (and maybe other monsters, needs testing).

Slugcat Interaction
Generally passive and non-hostile, these long worms bend their flexible bodies to observe Slugcat, until he approaches too close, in which the garbage worm will retract back where it had sprouted from. Before retracting however, these creatures will usually try to steal Slugcat's spears. Smaller objects such as rubbish, pearls, and bombs won't get stolen.

Hitting garbage worms with weapons will make them hostile, indicated by a change in eye-color from white to red. In this state, they will attempt to drown Slugcat in the dirty water they spring from. If no water is available, they'll just fling you around. Hitting a garbage worm will make all worms hostile until the following cycle.

Although garbage worms can be stunned and may temporarily retreat underground, they cannot be killed.

Developer's Note
The Developers have said on the Kickstarter page that while Garbage Worms generally leave your Slugcat alone, "always be cautious though ~ hunger has no law".

Trivia

 * Interestingly enough, when the rain arrives, garbage worms do not appear to flee from it, and instead simply wave around as usual, seemingly unbothered. Although it is entirely possible they retreat underground once the rain sufficiently obscures the screen.