The properties of the cuticle deposition rhythm in Riptortus pedestris. (a) Cross sections of the tibia of the hind leg 20 days after adult emergence under short-day conditions. Alternating double layers are clearly observed in intact individuals. Arrows indicate bright layers. Scale bar: 25 μm. (b) The number of bright layers in the endocuticle under light-dark cycles at a constant temperature (25°C; closed circles), temperature cycles under constant darkness (open circles) and constant darkness at a constant temperature (open diamonds; N = 9-16). The solid and broken lines show regression lines calculated from the data from day 1 to day 8. On days 3 and 6 the numbers of bright layers under light-dark cycles were not significantly different from those under constant darkness (t-test, P > 0.05). The numbers of layers deposited under temperature cycles were one fewer than those under light-dark cycles, suggesting that the rhythm takes a little longer to entrain to temperature cycles. (c) The numbers of bright layers at day 6 (144 h after adult emergence) under light-dark cycles at 25°C (left) and temperature cycles under constant darkness (right; N = 11-16). The solid lines show hyperbolae, which are the equations when the rhythm completely entrains to the environmental cycles. The data of T = 24 in the left panel were from (b). Asterisks indicate significant differences between the mean number of bright layers and the hypothesized value (t-test, ** P < 0.01). (d) The number of bright layers on day 6 at 22.5°C, 25°C and 27.5°C under constant darkness. There were no significant differences in the number of bright layers among three temperatures (ANOVA, P > 0.05). N = 11-13. The data at 25°C are from (b). The Q10 value was 1.03.