- Earthworm photoreceptors are located in nerve fibers in the skin. These nerve fibers are connected to special nerves called ganglia, which connect to an earthworm's version of a brain. The brain, called a ganglion, helps trigger chemical reactions to control the entire body of the worm.
- Earthworms soon dry out and die if exposed to warmth and sunlight. They need to stay underground in moist dirt to survive. If any part of a worm is exposed to light as it tunnels, the worm is alerted through the photoreceptors and can quickly react to get back to safer ground.
- Earthworm photoreceptors can detect the intensity of different colored lights. Earthworms move away from white or blue light, but they do not react to red light.