[01] Shigeru Kikukawa, Biological Institute, Faculty of Science, University of Toyama, Toyama, Japan. [02] Yuta Kakihara, Biological Institute, Faculty of Science, University of Toyama, Toyama, Japan. [03] Yuki Okano, Biological Institute, Faculty of Science, University of Toyama, Toyama, Japan. [04] Renpei Shindou, Biological Institute, Faculty of Science, University of Toyama, Toyama, Japan. [05] Naoyuki Sugino, Biological Institute, Faculty of Science, University of Toyama, Toyama, Japan. [06] Jinnai Tsunekawa, Biological Institute, Faculty of Science, University of Toyama, Toyama, Japan. [07] Akihiro Yasui, Biological Institute, Faculty of Science, University of Toyama, Toyama, Japan. [08] Kazuhito Yoneda, Biological Institute, Faculty of Science, University of Toyama, Toyama, Japan.

The present study focuses on the adult eclosion rhythm of the Indian meal moth, Plodia interpunctella Hübner (Lepidoptera: Pyralidae), under two non-24 h thermocycles of 30°C/20°C and 25.5°C/24.5°C in constant darkness (DD). The thermocycles were provided as two combinations: one with a constant 12-h thermophase (T) alternated with a cryophase (C) of varying durations (6-18 h) and the other with a constant 12-h C alternated with varying durations (6-18 h) of the T. For 30°C/20°C thermocycle with a constant 12-h T, the temporal position of the adult eclosion peak is observed to advance as the cycle length extends. The peak occurs within the T and appears at about 17 h after the temperature-fall. However, when the duration of the C is constant for 12 h, the average peak time of adult eclsion is Zt 5.0 after the temperature rises. Under the 25.5°C/24.5°C thermocycle, the temporal position of the adult eclosion peak is a function of the cycle length. As the insects do not experience non-24 h thermocycles in nature, our results provide clues to the basic nature of the time-keeping mechanism of P. interpunctella.

Adult Eclosion Rhythm, Indian Meal Moth, Plodia interpunctella, Non-24 h Thermoperiod

[01] Kikukawa, S., Hashizume, R., Honda, M., Inoue, Y., Maekawa, T., Sakata, R., Takahashi, N., Tanaka, K. & Uchida, Y., 2013 Adult eclosion rhythm of the Indian meal moth Plodia interpunctella: response to various thermocycles with different means and amplitudes. Physiological Entomology, 38: 253-259. [02] Aschoff, J., 1965 Circadian Clocks, North-Holland, Amsterdam. [03] Beck, S.D., 1980 Insect Photoperiodism, 2^nd edn. Academic Press, New York. [04] Saunders, D.S., 2002 Insect Clocks, 3^rd edn. Elsevier, The Netherlands. [05] Refinetti, R., 2006 Circadian Physiology, 2^nd edn. Taylor & Francis, London. [06] Kikukawa, S., Hashizume, R., Honda, M., Inoue, Y., Maekawa, T., Sakata, R., Takahashi, N., Tanaka, K. & Uchida, Y., 2012 Effects of photoperiod and temperature on the rhythm and free-running of adult eclosion in the Indian meal moth Plodia interpunctella. Physiological Entomology, 37: 258-265. [07] Arai, T., 1976 Effects of temperature and light-dark cycles on the diel rhythm of emergence in the Oriental fruit fly, Dacus dorsalis Hendel (Diptera: Trypetidae). Japanese Journal of Applied Entomology and Zoology, 20: 69-76. (In Japanese). [08] Arai, T., 1998 Egg hatching rhythms of Eobiana engelhardti subtrolpica Bey-Bienko (Orthoptera: Tettigoniidae) under non-24 h thermoperiods. Entomological Science, 1: 495-501. [09] Masaki, S. & Kikukawa, S., 1981 The diapause clock in a moth: response to temperature signals. Biological Clocks in Seasonal Reproductive Cycles (ed. by B.K. Follett), pp. 101-112. J. Wright & Sons, U.K. [10] Kikukawa, S. & Masaki, S., 1984 Interacting effects of photophase and scotophase on the diapause response of the Indian meal moth, Plodia interpunctella. Journal of Insect Physiology, 30: 919-925.