A light-sensitive cell on the surface of an animal's body. This simple eye form cannot gather enough information to see an image; it only detects changes in light and dark. Eyespots can be found on simple organisms such as earthworms and leeches. When the eyespot is stimulated by sunlight, the organisim reacts by moving out of the light. Eyespots can also be found on more complex animals that have well-developed eyes. A dragonfly, for example, has an eyespot on each side of its head in addition to its compound eyes. Since eyespots only detect changes in light and dark, the dragonfly may be using them as navigation aids -- by tracking the horizon where the light sky meets the dark ground.

swelled area attached to a flagella that contains pigment. The pigment proteins respond to the presence of light and signal the flagella to move toward it.

(stigma) A special photoreceptive structure found at the base of the flagellum in some autotrophic protists. Functions to detect light.

A pattern of scales on a butterfly's wings resembling an eye, often with rims and pupils of contrasting colours

A mark found on some caterpillars and butterflies. It is round and has a spot in the center (the "pupil") of a different color.[ image

an eyelike marking (as on the wings of some butterflies); usually a spot of color inside a ring of another color

or Occelli

a coloration on the body of an animal that looks like an eye and serves to fool predators as to the location of that animal's head; a type of defense mechanism employed by animals.