Effect of Light Intensity on the Time of Egg Hatch in Metrioptera hime FURUKAWA (Orthoptera : Tettigoniidae)

When eggs of Metrioptera hime were kept under daily cycles of change in light intensity, they mainly hatched within 2 h after the rise of light intensity. When eggs were exposed to a single signal of lowering light intensity, they hatched around 12-14 h after the signal provided that the drop in light intensity was large. A single signal of increse in light intensity also triggered hatching. When eggs were exposed to various light intensities (400, 100, 10 and 1 lux) under a thermoperiod (25 : 15℃, each 12 h), eggs hatched during the low temperature phase. However, the lower the light intensity, the later the time of hatching after the temperature fall. The same result was observed with a single signal of temperature fall.