Can a worm see?
Contrary to the popular cartoon image of worms, they have no eyes and cannot see. They are, however, sensitive to light, particularly at their front ends. If a worm has been in the dark and is then exposed to bright light, it will quickly try to move away from the light. A night crawler, for example, will immediately retract into its burrow if you shine a flashlight on it some wet spring night. The sensory cells in a worm’s skin are less sensitive to red light than to light of mixed wavelengths. If you want to observe worms under less intrusive conditions, you can take advantage of this fact by placing red cellophane or an amber bread wrapper over your light source. You can make further observations of earthworm behavior in a photographic darkroom using a red safe light. Your eyes will adapt to the lower level of light these aids provide, and the worm will move more naturally than it does under bright light.
