Abstract
Summary
Hyla versicolor responds to light by melanophore expansion, and to darkness by contraction. The completenes of contraction depends upon duration of the period of dark-adaptation, generally more than 72 hours are required for all frogs to turn green. The change to brown after dark-adaptation is variable and no consistent relationship has been found between length of darkness and length of recovery period. Temperatures of 3-5° C darken frogs as does light. Light and cold appear to be stimuli which cause release of mel-anophorotropic hormone (ACTH?) from the pituitary gland. Light-induced changes, opposite to those shown by other frogs, seem explicable on the basis of natural selection during the diurnal period when these frogs are inactive.
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