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.

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.

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。

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.

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.

The seasonal life cycle of the zygaenid moth, Pseudopidorus fasciata is complicated by two different developmental arrests: a winter diapause as a fourth larval instar and a summer diapause as a prepupa in a cocoon. Both larval diapause induction and termination are under photoperiodic control. Short days induce larval diapause with a critical daylength of 13.5 h and long days terminate diapause with a critical daylength of 14 h. In the present study photoperiodic control of summer diapause was investigated in Pseudopidorus fasciata. Under long photoperiods ranging from LD 14:10 to LD 18:6, only part of the population entered summer diapause, the rest continued to develop. The lowest number of prepupae entered diapause at LD 14:10, followed by LD 16:8 and LD 17:7. The highest incidence of diapause occurred with photoperiods of LD 15:9 and LD 18:6. By transferring the diapausing prepupae induced by various long photoperiods (LD 14:10, LD 15:9, LD 16:8, LD 17:7, LD 18:6) to LD 13:11, 25 1C, the duration of diapause induced by LD 14:10 was significantly shorter than those induced by longer photoperiods. By keeping aestivating prepupae induced by LD 15:9, 28 1C or by natural conditions at short photoperiods (LD 11:13 and LD 13:11) and at a long photoperiod (LD 15:9), the duration of diapause at LD 15:9 was more than twice as long as than those at LD 11:13 and LD 13:11. Moreover, adult emergence was highly dispersed with a high mortality at LD 15:9 but was synchronized with low mortality at LD 11:13 and LD 13:11. When the naturally induced aestivating prepupae were kept under natural conditions, the early aestivating prepupae formed in May exhibited a long duration of diapause (mean 126 days), whereas the later-aestivating prepupae formed in July exhibited a short duration of diapause (mean 69 days). These results indicate that aestivating prepupae require short or shortening photoperiod to terminate their diapause successfully. By transferring naturally induced aestivating prepupae to 25, 28 and 30▫C, the duration of diapause at the high temperature of 30▫C was significantly longer than those at 25 and 28▫C, suggesting that high temperature during summer also plays an important role in the maintenance of summer diapause in Pseudopidorus fasciata. All results reveal that summer diapause can serve as a ‘‘bet hedging’’ against unpredictable risks due to fluctuating environments or as a feedback mechanism to synchronize the period of autumn emergence. © 2006 Published by Elsevier Ltd.

大猿叶虫Colaphellus bowringi是江西山区十字花科蔬菜上的重要食叶害虫，以成虫在土中越夏和越冬。由于成虫滞育期的差异，该虫的化性显示了明显的种内变异。有些个体隔年繁殖；有些个体是一化性的，仅在春季或秋季繁殖1代；有些个体是二化性的，春季和秋季各繁殖1代；有些个体是多化性的，春季1代，秋季2～3代。因此，大猿叶虫在田间一年可发生4代。在春季，滞育成虫于2月底至4月初陆续出土繁殖；在秋季，滞育成虫于8月中旬至10月初陆续出土繁殖。春季羽化的成虫于4月底至6月上旬陆续入土越夏，秋季羽化的成虫于9月中旬至12月底陆续入土越冬。大猿叶虫一生能交配多次，大多数雌虫的产卵期超过1个月，最长达67天。平均每雌产卵量；春季世代为644粒，秋季世代为963粒，最高达1950粒。各虫态的发育历期：在15～30℃间，卵为13.78～3.14天，幼虫为22.83～6.95天，蛹为12.10～3.18天。发育阈值温度：卵为10.7 ℃，幼虫为8.8 ℃，蛹为9.6 ℃。非滞育成虫的寿命约为1～2个月，滞育成虫的寿命为5～38个月。滞育成虫均入土蛰伏，在土中的蛰伏深度为9～31cm。

w a great difference in diapause duration (from several months to more than 3 years) under natural conditions. The effects of diapause duration on future reproduction in the beetle are investigated at 25▫C with an LD 14: 10 h photoperiod and under natural conditions. The fecundity of postdiapause adults with a short diapause of 5 months and nondiapause adults is similar, showing that a short diapause has no affect on reproduction, whereas the longevity of postdiapause adults with a short diapause of 5 months is significantly shorter than nondiapause adults, showing that a short diapause has a negative affect on longevity. The mean total egg production per female and longevities of postdiapause adults with long diapause periods of 16, 22, 29 and 34 months are similar to nondiapause adults, but the mean daily egg production per female is significantly higher than nondiapause adults, showing that extended diapause has a positive effect on postdiapause reproduction. The offspring of postdiapause parents require a relatively shorter time for egg development compared with the offspring of nondiapause parents, showing that diapause has a positive effect on their offspring’s performance. However, there are no significant differences among offspring performance in terms of survival, adult longevity, mean egg production per female and mean daily egg production per female.

Dendrolimus tabulaeformis overwinters as third to fourth instar larvae at short days in autumn. Using 24-h light–dark cycles, the photoperiodic response curves were similar at 24 and 28▫C. The critical night length was 9 h 20 min at 24▫C and 9 h 50 min at 28▫C. Under non-24 h light–dark cycles, duration of scotophase proved crucial in the determination of diapause. In night interruption experiments using 24-h light–dark cycle, a 1-h light pulse falling 8 h in the darkness strongly averted diapause in comparison with other light pulses. Nanda–Hamner experiments showed two weak troughs of diapause inhibition, suggesting the possible involvement of the circadian system. However, Bünsow experiments did not support the evidence of the involvement of circadian oscillatory system in photoperiodic time measurement. These results suggest that photoperiodic time measurement in this moth shows a non-oscillatory ‘hourglass-like’ response model or a rapidly damping oscillator model.

The effects of thermoperiods on diapause induction in continuous darkness or under a 12: 12h LD photoperiod were investigated in the cabbage beetle, Colaphellus bowringi Baly, a typical short-day species. The diapause response curves both at different constant temperatures and at the thermocycle of format CT x: (24-x) h (16: 28▫C) under continuously dark rearing conditions showed that the incidence of diapause depended mainly on whether or not the mean temperature was≤20▫C or ≥20▫C. If the mean temperature was≤20▫C, all individuals entered diapause; if >20▫C, the incidence of diapause declined gradually with increasing mean temperatures. The thermocycle (CT 12: 12h) with a series of different cryophases (8–22▫C) and thermophases (24–32▫C) under continuous darkness demonstrated a cryophase response threshold temperature of approximately 19▫C and a thermophase response threshold temperature of approximately 31▫C. Thermoperiodic amplitude (temperature difference between cryophase and thermophase) was shown to have a significant influence on diapause induction at the mean temperatures of 22, 23 and 24▫C, but not at ≥25▫C. Thermoperiodic responses under LD 12: 12h clearly showed that the incidence of diapause was influenced strongly by the photophase temperature. The thermoperiod under LD 12: 12h induced a much lower incidence of diapause than the thermoperiod with the same temperature in continuous darkness. The ecological significance of thermoperiodic induction of diapause in this species is discussed.