Locomotor Activity Rhythm under Natural Conditions and the Effect of Temperature on the Rhythm in the Band-Legged Ground Cricket, Dianemobius nigrofasciatus

<i>Dianemobius nigrofasciatus</i> (Orthoptera: Trigonidiidae) shows a circadian rhythm in locomotor activity. In the present study, we recorded the locomotor activity of male adults under naturally fluctuating temperature and light conditions over a long period in both summer and autumn. The results showed that the onset time of locomotor activity was later on warmer days in summer, and the cessation time was earlier on cooler days in autumn. The delay in the onset time was also observed under laboratory conditions when a high temperature was added in the late photophase. When the high temperature period was removed, the onset of activity immediately returned to the original time of day. Thus, the high temperature did not alter the circadian phase but directly suppressed locomotor activity through a masking effect.