本文报道了高温(31℃)对环带锦斑蛾幼虫滞育发生的抑制作用。当幼虫暴露于31℃时,所有个体都继续发育，与光周期无关。在诱导滞育的光周期条件(L12:D12)下，光期的高温配合不同的暗期低温(15～28℃)，导致几乎所有个体滞育,但当暗期为5℃时,滞育率反而下降；相反，当光期的低温配合不同持续时间的暗期高温(31℃)时，则几乎所有的个体都继续发育，这说明高温在暗期发挥着重要的作用。在暗期给予不同时间长度(2、4、6、8、10、12 h) 的高温处理，结果表明一个2 h的高温处理就能有效地抑制滞育的发生。在暗期的不同时间给予4 h高温处理，显示了幼虫在暗期开始后的第一个4 h (18:00～22:00)对高温最敏感,完全抑制了滞育的发生。最后讨论了高温调节滞育机制在该虫生活史上的适应意义。

The cabbage beetle, Colaphellus bowringi, is a short-day species undergoing an imaginal summer and winter diapause. Its photoperiodic response highly depends on temperature. All adults entered diapause at ≤20▫C regardless of photoperiods. High temperatures strongly weakened the diapause-inducing effects of long daylengths. The diapause-averting influence of short daylengths was expressed only at high temperatures (above 20▫C). This indicates that the beetle has a cryptic ability to reproduce in summer. In fact, summer and winter diapause were induced principally by relatively low temperatures in the field, whereas photoperiod had less influence on diapause induction. The critical daylength for the autumnal population was between 12 h and 13 h. By transferring from a long day to a short day or vice versa at different times after hatching, it was shown that the sensitive stage with regard to photoperiod was the larva, whereas a long day was photoperiodically more potent than a short day. The sensitive stage to temperature encompassed the larval, pupal and adult stages. This different response pattern serves to ensure that the beetle enters summer and winter diapause in time. The selections for non-diapause trait under laboratory (at 25▫C) and natural conditions (at >24▫C) showed that the beetle could lose its sensitivity to photoperiod very rapidly. ©2002 Elsevier Science Ltd. All rights reserved.

In the zygaenid moth, Pseudopidorus fasciata, both larval diapause induction and termination are under photoperiodic control. In this study, we investigated whether photoperiodic time measurement (with a 24-h light–dark cycle) in this moth is qualitative or quantitative. Photoperiodic response curves, at 22, 25, and 28 1C indicated that the incidence of diapause depended on whether the scotophases exceeded the critical night length (CNL) or not. All scotophases longer than the CNL-induced diapause; all scotophases shorter than the CNL-inhibited diapause. The CNL was 10.5 h at 25 and 28▫C, and 10 h at 22▫C. By transferring from various short photoperiods (LD 8:16, LD 9:15, LD 10:14, LD 11:13, LD 12:12, and LD 13:11) to a long photoperiod (LD 16:8) at different times, the number of light–dark cycles required for 50% diapause induction at 25 1C was 7.14 at LD 8:16, 7.2 at LD 9:15, 7.19 at LD 10:14, 7.16 at LD 11:13, and 7.13 at LD 12:12, without showing a significant difference between the treatments. Only at LD 13:11 (near the CNL), the number of light–dark cycles was significantly increased to 7.64. The intensity of diapause induced under different short photoperiods (LD 8:16, LD 9:15, LD 10:14, LD 11:13, and LD 12:12) at 25 1C was not significantly different with an average diapause duration of 36 days. The duration of diapause induced under LD 13:11 was significantly reduced to 32 days. All results indicate that the night-lengths are measured as either ‘‘long’’ or ‘‘short’’ compared with some critical value and suggest that photoperiodic time measurement for diapause induction in this moth is based on a qualitative principle.

Induction of larval diapause is a photoperiodically controlled event in the life history of the moth Pseudopidorus fasciata. In the present study, the photoperiodic counter of diapause induction has been systematically investigated. The required day number (RDN) for a 50% response was determined by transferring from a short night (LD 16:8) to a long night (LD 12:12) or vice versa at different times after hatching, The RND differed significantly between short- and long-night cycles at different temperatures. The RDN for long-night cycles at 20, 22, 25 and 28▫C was 11.5, 9.5, 7.5 and 8.5 days, respectively. The RDN for short-night cycles was 3 days at 22▫C and 5 days at 20 1C indicating that the effect of one short night was equivalent to the effect of 2–3 long nights effect. Night-interruption experiments of 24 h photoperiods by a 1 h light pulse showed that the most crucial event for the photoperiodic time measurement in this moth was whether the length of pre-interruption (D1) or the post-interruption (D2) scotophases exceeded the critical night length (10.5 h). If D1 or D2 exceeded 10.5 h diapause was induced. The diapause-averting effect of a single short-night cycle (LD 16:8) against a background of long nights (LD 12:12) showed that the photoperiodic sensitivity was greatest during the first 7 days of the larval period and the highest sensitivity was on the fourth day. Both non-24 and 24 h light-dark cycle experiments revealed that the photoperiodic counter in P. fasciata is able to accumulate both long and short nights during the photosensitive period, but in different ways. The information from short-night cycles seems to be accumulated one by one in contrast to long-night cycles where six successive cycles were necessary for about 50% diapause induction and eight cycles for about 90% diapause. These results suggest the accumulation of long-night and short-night cycles may be based on different mechanisms.

Photoperiodic control of diapause induction was investigated in the short-day species, Colaphellus bowringi, which enters summer and winter diapause as adult in the soil. Photoperiodic responses at 25 and 28▫C revealed a critical night length between 10 and 12 h; night lengths ≥12 h prevented diapause, whereas night lengths <12 h induced summer diapause in different degree. Experiments using non-24-h light–dark cycles showed that the duration of scotophase played an essential role in the determination of diapause. Night-interruption experiments with T=24 h showed that diapause was effectively induced by a 2-h light pulse in most scotophases; whereas day-interruption experiments by a 2-h dark break had a little effect on the incidence of diapause. The experiments of alternating short-night cycles (LD 16:8) and long-night cycles (LD 12:12) during the sensitive larval period showed that the information of short nights as well as long nights could be accumulated. Nanda–Hamner experiments showed three declining peaks of diapause at 24 h circadian intervals. Bünsow experiments showed two very weak peaks for diapause induction, one being 8 h after lights-off, and another 8 h before lights-on, but it did not show peaks of diapause at a 24 h interval. These results suggest that the circadian oscillatory system constitutes a part of the photoperiodic clock of this beetle but plays a limited role in its photoperiodic time measurement.