Insects and the Length of the Day.

The article discusses the physiological behavior of insects and animals. The authors considers day length, or photoperiod as factors that affects the physiology of both animals and plants. It controls the diurnal change in the shell color of the fiddler crab and the seasonal variation in the fur color of the snowshoe hare. The gradual change in the photoperiod throughout the year forms the most precise basis known for the timing of biological events.