Effect of photoperiod and temperature on diapause in a Florida strain of the tropical warehouse moth Ephestia cautella

A photoperiodically-controlled diapause of the long-day, short-day type was identified in a brown-winged, yellow-eyed strain of Ephestia cautella (Walker). The proportion of larvae diapausing in very long photoperiods was less than in short photoperiods. The mean critical photoperiod, here defined as that photoperiod giving half the maximum percentage of insects that diapause in response to photoperiod at a given temperature, was between 12 and 13 hr for the long-day reaction at both 20 and 25°C. The principal sensitive phase occurred near the time of the last larval moult. The mean duration of diapause was 2–3 months at 20°C and slightly longer at 25°C. The optimum temperature for diapause development was near 15°C, all larvae pupating within 24 days after a 45-day exposure at this temperature. Diapause could be terminated whenever larvae diapausing at 20°C were exposed to as few as five long (15 hr) photoperiods at 25°C. Long photoperiods at 20°C, or short photoperiods (9 hr) at 25°C were less effective in terminating diapause.     

Seasonal diapause development and diapause termination in the European skipper, Thymelicus lineola (Ochs.)

Eggs of the European skipper, Thymelicus lineola, containing pharate first-instar larvae were brought into the laboratory at the beginning of each month from September to May and maintained at 20°C, 14L:10D. No emergence was observed within 40 days of collection before December. From that time on, while total emergence was similar, the duration of the emergence period decreased over the season from > 120 days in December to < 14 days in May. There was however no marked change in the seasonal supercooling point values of diapausing larvae.The rate of emergence from eggs collected in March was influenced by photoperiod, being slower under short-day conditions. However for any given photoperiod tested, the rate of emergence increased with an increase in temperature. The possible adaptive significance of a two-phase diapause, where diapause termination is photoperiodically controlled in species that overwinter as an egg or as a pharate first-instar larva within the egg chorion in exposed habitats, is discussed.     

On the factors inducing the inhibition of diapause in the progeny of diapause females of Trichogramma telengai

The ability to enter diapause in the progeny of Trichogramma Westw. (Hymenoptera: Trichogrammatidae) females that have undergone diapause is markedly reduced or even completely absent. This maternal inhibition of diapause can result from three types of factors: (i) environmental factors that induce maternal diapause; (ii) maternal diapause itself; and (iii) diapause‐terminating environmental factors. The present study aims to determine the factors that prevent diapause in the progeny of a Trichogramma telengai Sor. generation that has undergone diapause. Different tendencies to enter diapause in the maternal generation are induced by different photoperiods (LD 12 : 12 h, 16 : 8 h and 18 : 6 h) during development of the grandmaternal generation and different temperatures (from 10 to 15 °C) during larval development of the maternal generation. To terminate diapause, prepupae of the maternal generation are kept at 4–5 °C in the dark. To estimate the ability to enter diapause, the progeny generation is incubated at 14 °C. The results suggest that the inhibition of the tendency to enter diapause in the progeny of T. telengai females that have undergone diapause is caused by diapause itself rather than by diapause‐inducing or diapause‐terminating environmental factors. This result can be used to clarify the mechanism of the inhibition of diapause in the progeny of females that have undergone diapause.     

Photoperiodic and temperature effects on the intensity of larval diapause in Sesamia nonagrioides

Abstract. The intensity of larval diapause in Sesamia nonagrioides Lef (Lepidoptera: Noctuidae) was investigated under laboratory conditions. Newly hatched larvae were exposed to different stationary photoperiods (from LD 7 : 17 h to LD 14 : 10 h), at a constant temperature of 25 °C. Diapause incidence was higher when larvae were exposed to daylengths shorter than the critical value (LD 12 : 12 h), whereas the within‐treatment variation in the larval period appeared to be significantly correlated with the photoperiod applied. The incidences of diapause and the duration of larval development were also measured after exposing larvae to short photoperiods (LD 8 : 16 h, LD 10 : 14 h or LD 12 : 12 h) in combination with various temperatures (20, 22.5 or 25 °C). Although an increase in the incidence of diapause appeared with the lowering of the temperature, no statistical differences were observed in the time needed for pupation within the photoperiodic treatments at the temperatures of 20 and 22.5 °C. Furthermore, when diapausing larvae were transferred to the long photoperiod of LD 16 : 8 h, they immediately proceeded to pupation, regardless of the photoperiod or the temperature to which they had been previously exposed, indicating that there were no differences in the intensity of diapause. Photoperiodic changes from LD 10 : 14 h to LD 12 : 12 h or to LD 14 : 10 h at different larval ages reduced the intensity of diapause with (a) early age of transfer and (b) increase of daylength. By contrast, when larvae were transferred from the long photoperiod of LD 14 : 10 h to shorter, such as LD 10 : 14 h or LD 12 : 12 h, a small increase in the intensity of diapause with the shortening of the daylength was apparent. These results support the hypothesis that insects may compare the duration of the photoperiod and could classify them as either longer or shorter in relation to the critical value.     

The regulation of development during diapause in Ephestia elutella (Hübner) by temperature and photoperiod

Diapausing larvae of Ephestia elutella reared at 20°C in short photoperiods (LD 11:13), and then maintained 12 weeks or longer at 5–15°C before transfer to 20 or 25°C, pupated sooner than unchilled controls. At 25°C, all samples kept in long photoperiods (LD 15:9) survived better and pupated faster than similarly treated samples held in short photoperiods (LD 9:15). Samples kept at 20°C after chilling pupated much slower than those at 25°C, and, except after exposure at 5°C, pupated at similar rates at LD 11:13 or 15:9, although mortality was higher at the shorter photoperiod. After exposure at 5°C, larvae required increased day-length as well as increased temperature to hasten pupation whereas after exposure at 10°C most responded to increased temperature only.For samples maintained in slightly heated or unheated outbuildings, the summer emergence was poorly synchronized and males on average emerged ahead of females. Samples moved from the unheated outbuilding to 25°C and long days in the laboratory in early spring, however, pupated quickly and males and females emerged together. A late phase of diapause development thus exists requiring both high temperature and long photoperiods to ensure a prompt resumption of morphogenesis. Spring temperatures in the United Kingdom are seldom high enough to synchronize the completion of diapause.     

Maternal thermal and photoperiodic effects on the progeny diapause in Trichogramma telengai Sorokina (Hymenoptera: Trichogrammatidae)

Although maternal photoperiodic and maternal thermal effects on the progeny diapause have been demonstrated in a number of insect species, their interaction has been rarely studied. We investigated this interaction in Trichogramma telengai. In a series of experiments, maternal females were reared at day lengths of 12–18 h and at temperatures of 17, 20, 25 and 30°C. Their progeny developed under day length of 12 h and temperatures of 13, 14 and 15°C. The experiments showed that both short day and low temperature experienced by the maternal generation significantly increased the proportion of diapausing progeny. In particular, the threshold of the maternal photoperiodic response decreased with temperature. Under combinations of photoperiod with daily thermoperiod, the role of the “night” temperature in the induction of diapause in the progeny was much more important than that of the “day” temperature. We conclude that the interaction pattern between the photoperiodic and thermal maternal effects in T. telengai is generally the same as that between the photoperiodic and thermal responses directly influencing diapause induction in other long‐day insects. The threshold temperature of the maternal thermal response of T. telengai was about 25–27°C, while diapause can be induced if larvae develop at temperatures not higher than 15–16°C. This suggests that, at least in the studied Trichogramma species, the maternal thermal effect has no ecological value. In the practice of biocontrol, however, rearing of Trichogramma wasps at high temperature can drastically reduce the proportion of diapausing progeny.     

Effects of photoperiod and temperature on diapause induction and termination in the swallowtail,Sericinus montelus

Abstract Sericinus montelus overwinters as diapausing pupae. In the present study, the effects of photoperiod and temperature on diapause induction and termination of diapause are investigated. The results obtained demonstrate that high temperature can reverse the effect of short day‐lengths on diapause induction. Under an LD 12 : 12 h photoperiod, all pupae enter diapause at 15, 20 and 25 °C, whereas all pupae develop without diapause at 35 °C. No pupae enter diapause under an LD 14 : 10 h photoperiod when the temperature is above 20 °C. Photoperiodic response curves obtained at 25 and 30 °C indicate that S. montelus is a long‐day species and the critical day‐length is approximately 13 h at 25 °C. At 25 °C, the duration of diapause is shortest when the diapausing pupae are maintained under an LD 16 : 8 h photoperiod and increases under LD 14 : 10 h and LD 12 : 12 h photoperiods. Under an LD 16 : 8 h photoperiod, the duration of diapause is shortest when the diapausing pupae are maintained at 25 °C, followed by 20 and 30 °C, and then at 15 °C. These results suggest that a moderate temperature favours diapause development under a diapause‐averting photoperiod in this species. The duration of diapause induced by an LD 12 : 12 h photoperiod is significantly longer at 25 °C than those at 15, 20 and 30 °C, and is shortest at 15 °C. At 25 °C, the duration of diapause induced by LD 6 : 18, LD 12 : 12 and LD 13 : 11 h photoperiods is similar and longer than 90 days. Thus, the diapause‐inducing conditions may affect diapause intensity and a photoperiod close to the critical day‐length has significant influence on diapause intensity in S. montelus.     

Cold‐induced expression of diapause in Praon volucre: fitness cost and morpho‐physiological characterization

Cold exposure (2°C for 7 days) in constant darkness at mummy stage induces diapause expression in 9% of the Praon volucre Haliday population. Diapausing parasitoids show a significant delay in emergence time compared with nondiapausing counterparts. A diapause‐mediated polyphenism is observed in mummy colour, with diapausing mummies being clearly darker than nondiapausing ones. The diapause status of dark mummies is confirmed by a significant reduction in metabolic rate. Diapausing parasitoids also display specific morphological characteristics: they are heavier (fresh and dry mass) and accumulate larger fat reserves than nondiapausing counterparts. The diapause status is associated with a fitness cost in terms of adult longevity. There is no evidence of diapause‐related change in supercooling ability.     

茧蜂滞育的研究进展

滞育现象在多种茧蜂类天敌昆虫中存在, 通过调控茧蜂滞育, 可达到延长产品货架期、延长防控作用时间、提高产品的抗逆性和繁殖力的目标, 对茧蜂的扩繁和应用具有重要意义。本文通过总结1910年以来的2 545篇国内外滞育文献, 统计得出有明确滞育诱导或滞育解除报道的茧蜂有37种, 分属7亚科16属, 其中对滞育特征有详细描述的有23种。茧蜂大多以预蛹进入滞育, 其次为幼虫滞育, 少数为成虫滞育, 其滞育敏感阶段因种不同而异。滞育持续期相对较长, 大多可维持数月, 最长的可达14个月。光周期、温度和寄主是影响茧蜂滞育的主要因子, 湿度、亲代和寄主植物也可在一定程度上影响滞育进程。目前, 茧蜂滞育的研究仅限于生物学观察阶段, 对茧蜂滞育的生理学特征、激素调控和分子调控等尚未有研究报道, 有许多问题有待进一步探讨。     

Adult diapause in the Colorado potato beetle, Leptinotarsa decemlineata: effects of external factors on maintenance, termination and post-diapause development

ABSTRACT. This study tests the effects of temperature, water, food and photoperiod on breaking diapause and resumption of activity (emergence from the soil) in Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae) diapausing under natural winter conditions or at constant temperatures in the laboratory. Behavioural and physiological criteria were used to characterize the various phases of diapause. Three successive phases are distinguished during hibernation: 'diapause development' or true diapause, a facultative 'post-diapause quiescence' and, finally, a transient phase of post-diapause development leading to emergence from the soil. Diapause development is completed within 3 months in the field and its duration depends on temperature. Although they are buried in the soil during this phase, beetles remain sensitive to photoperiod when artificially exposed to it. They do not emerge from the soil when exposed to higher temperatures. Thereafter, they stay in a quiescent state maintained by low temperature, low humidity or lack of food. The response to temperature changes during hibernation. In the soil, activity begins when soil temperature reaches 4–5C, but this temperature is too low to permit postdiapause development. The transient phase has a temperature threshold between 8 and 10C, whereas emergence from the soil occurs only when the temperature exceeds 11C. Post-diapause development is influenced strongly by temperature and humidity. After emergence, post-diapause development leads eventually to reproduction. Food is essential for reproduction after diapause whereas photoperiod plays no further role.     

Response of females of the braconid parasitoid Microplitis demolitor to frass of larvae of the Noctoids, Heliothis zea and Trichoplusia ni and to 13-methylhentriacontane

Microplitis demolitor Wilkinson, a solitary larval parasitoid of several species of Noctuidae, has been imported into the United States from Australia. A closely related species, Microplitis croceipes (Cresson), is native to the United States. The host-selection behavior of M. demolitor females is similar to that of M. croceipes in that it is stimulated by kairomones (including 13-methylhentriacontane) in the frass of Heliothis zea (Boddie) larvae, larval diet affects the kairomonal activity of the frass, and exposure to frass prior to release stimulates host-selection behavior. M. demolitor females also respond to frass from Trichoplusia ni (Hübner) larvae that had fed on Pink Eye Purple Hull Cowpea cotyledons.

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Réponse de femelles de Microplitis demolitor sur la nourriture de chenilles de noctuelles et sur 13-methylhentriacontane

Résumé Microplitis demolitor, un parasitoïde solitaire de plusieurs espèces de chenilles de noctuelles, a été introduit d'Australie aux Etats-Unis comme agent potentiel de contrôle biologique. Les fèces des chenilles d'Heliothis zea et Trichoplusia ni élevées sur des cotyledons de pois (Pink Eye Purple Hull Cowpea) stimulent les femelles à sélectionner un hôte, mais les fèces des chenilles des deux espèces élevées sur diète CSM ne possèdent pas cette activité. Un extrait hexanique des fèces des chenilles de H. zea élevées sur cotyledons de pois stimule également ce comportement, de même que le 13-methylhentriacontane, substance présente dans les fèces des chenilles de H. zea (Jones et al., 1971). Les femelles de M. demolitor exposées immédiatement avant leur lâcher en serre aux fèces des chenilles de H. zea, nourries de cotyledons de pois, parasitent un plus fort pourcentage (41.7%) de chenilles de H. zea que cells qui n'ont pas été exposées aux fèces (13.9%).Le comportement de sélection de l'hôte des femelles de M. demolitor est donc semblable à celui des femelles de Microplitis croceipes, un parasitoïde étroitement apparenté indigène des Etats-U-nis. La femelle, par exemple, est stimulée par une kairomone des fèces des larves de H. zea nourries sur des cotyledons de pois (incluant le 13-methyl-hentriacontane), la diète affecte l'activité kairomonale des fèces, et une exposition préalable aux fèces avant le lâcher stimule le comportement de sélection de l'hôte.La stimulation du comportement de sélection de l'hôte, au moment du lâcher peut être utilisée pour améliorer l'efficacité des lâchers des parasitoïdes dans les programmes de contrôle biologique.

     

中红侧沟茧蜂滞育诱导和滞育茧的冷藏

中红侧沟茧蜂Microplitis mediator (Haliday)是夜蛾科害虫低龄幼虫的重要寄生蜂。田间实验表明,在冀中地区秋季田间条件下,当日平均气温为21.5℃、日平均光照时间为12 h 33 min时,少数个体进入滞育;当气温降至17.9℃以下、日光照时间缩短到11 h 45 min以下时,全部个体进入滞育。室内模拟实验结果表明,在17～26℃、光照时间10～14 h范围内,随着温度的降低和光照时间的缩短,滞育率明显提高。高温能抵消短光照对滞育诱导的影响,在26℃下,短光照不能诱导滞育。因此,低温和短光照是诱导该种天敌昆虫滞育的主要因子。中红侧沟茧蜂感受滞育信号的敏感期为低龄幼虫期,以预蛹（茧）进入滞育。低龄幼虫感受滞育信号以后,需要在滞育环境中发育到老熟幼虫才能全部进入滞育。将室内诱导的滞育茧在4℃左右环境条件下冷藏240天,成蜂的羽化率和寄生能力与没有冷藏的非滞育茧差异不显著;冷藏300天,滞育茧仍有81.4%可以正常羽化。本项研究结果为中红侧沟茧蜂的规模化、标准化生产提供了科学的依据。     

Environmental conditions terminate reproductive diapause and influence pheromone perception in the long‐lived moth Caloptilia fraxinella

Reproductive diapause enables long‐lived insects to time mating with environmental conditions suitable for offspring development. Plasticity in the perception of pheromones used in sexual communication may enable mate‐finding at the appropriate time of year. The moth Caloptilia fraxinella (Ely) (Lepidoptera: Gracillariidae) undergoes a 9‐month reproductive diapause, during which the male response to pheromone is plastic and is highest during the period of reproductive activity. The mechanisms controlling this pheromone response plasticity are not well‐understood, and the aim of the present study is to determine the main factors involved. In the present study, the impact of temperature, photoperiod, juvenile hormone analogue (JHA) and adult nutrition on diapause termination are tested using electroantennogram (EAG) and behavioural response to pheromone in male C. fraxinella. Eclosion in a state of reproductive diapause occurs in most males; diapause is maintained under short‐day or cool conditions indoors, or under natural conditions outdoors. Exposure to long‐day, warm conditions over a period of 4 weeks causes a small number of males to become behaviourally responsive to pheromone; a larger number of males become behaviourally responsive over a period of 3 months of post‐eclosion. Treatment with a JHA impacts male EAG and the behavioural response to pheromone during the period of reproductive diapause. A carbohydrate food source is not required by reproductively active adult male C. fraxinella to respond to pheromone and express mate location behaviours. The main factors involved in controlling male pheromone response plasticity and the implications of these factors for the C. fraxinella population in its expanded range are discussed.     

Effects of putrescine on diapause induction and intensity,and post‐diapause development of Helicoverpa armigera

Effects of putrescine on diapause induction and intensity, and post‐diapause development in Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) from Wuhan, Hubei, China were studied in the laboratory at different temperatures and photoperiod conditions. The results showed a generally higher incidence of diapause in putrescine‐feeding groups. Putrescine feeding distinctly restricted the development of non‐diapause‐destined and diapause‐destined larvae, except at 0.01% putrescine concentration, which accelerated the development of larvae at 21 °C. Putrescine had no significant effect on the duration of diapause, although it inhibited the post‐diapause development of pupae. Photoperiod played a different role in diapause induction and post‐diapause development between 21 and 23 °C. Putrescine played a definite role in diapause induction and intensity, and post‐diapause development in H. armigera, and a significant interaction between putrescine, photophase, and temperature is to be expected.     

Shifting daylength regimes associated with range shifts alter aphid‐parasitoid community dynamics

With climate change leading to poleward range expansion of species, populations are exposed to new daylength regimes along latitudinal gradients. Daylength is a major factor affecting insect life cycles and activity patterns, so a range shift leading to new daylength regimes is likely to affect population dynamics and species interactions; however, the impact of daylength in isolation on ecological communities has not been studied so far. Here, we tested for the direct and indirect effects of two different daylengths on the dynamics of experimental multitrophic insect communities. We compared the community dynamics under “southern” summer conditions of 14.5‐hr daylight to “northern” summer conditions of 22‐hr daylight. We show that food web dynamics indeed respond to daylength with one aphid species (Acyrthosiphon pisum) reaching much lower population sizes at the northern daylength regime compared to under southern conditions. In contrast, in the same communities, another aphid species (Megoura viciae) reached higher population densities under northern conditions. This effect at the aphid level was driven by an indirect effect of daylength causing a change in competitive interaction strengths, with the different aphid species being more competitive at different daylength regimes. Additionally, increasing daylength also increased growth rates in M. viciae making it more competitive under summer long days. As such, the shift in daylength affected aphid population sizes by both direct and indirect effects, propagating through species interactions. However, contrary to expectations, parasitoids were not affected by daylength. Our results demonstrate that range expansion of whole communities due to climate change can indeed change interaction strengths between species within ecological communities with consequences for community dynamics. This study provides the first evidence of daylength affecting community dynamics, which could not be predicted from studying single species separately.     

温度和光周期对管侧沟茧蜂滞育诱导及滞育茧的低温冷藏

【目的】为明确诱导管侧沟茧蜂Microplitis tuberculifer 滞育的主要因子,在田间和室内研究了不同温度和光周期下管侧沟茧蜂的滞育率和滞育茧的最佳冷藏温度。【方法】田间实验分别从8月31日到9月25日每隔5 d在室外罩笼内释放管侧沟茧蜂寄生的粘虫幼虫,待寄生蜂结茧后统计子代蜂的滞育率。室内实验共设5个不同温度（16℃, 18℃, 20℃, 22℃和24℃）和7个不同光周期（6L:18D, 8L:16D, 10L:14D, 12L:12D, 14L:10D, 16L:8D和18L:6D）,分别统计寄生蜂在各个处理条件下的滞育率。【结果】在河北中部地区秋季自然条件下,8月底当日平均气温为24.4℃,日平均光照时间为12 h 51 min 时,少数蛹（5.08%）开始进入滞育;9月25日,当日平均气温为17.2℃,日平均光照时间为11 h 36 min以下时,几乎所有蛹个体进入滞育,滞育率达到99.70%。在室内人工控制条件下,当温度为22℃以上,无论光周期如何变化,管侧沟茧蜂不能进入滞育,所结茧全部为非滞育茧。温度为22℃以下存在光周期反应,在温度16℃, 18℃和20℃,光周期10L:14D时形成滞育茧数量最多,滞育率分别为100%, 89.75% 和 29.58%。可见温度和光周期二者共同影响管侧沟茧蜂的滞育。滞育茧在0℃左右条件下冷藏 240 d 和5℃左右环境条件下冷藏180 d, 成虫的羽化率和寄生能力与发育茧差异不显著(P>0.05);0℃条件下冷藏300 d,滞育茧仍有79%可以正常羽化。【结论】该寄生蜂在秋季进入滞育主要是低温条件和短光照反应相互作用的结果,滞育茧在0℃和5℃温度下至少可以保存240 d。这些结果对管侧沟茧蜂的大规模繁殖和滞育茧的保存具有重要参考价值。     

Effect of photoperiod experienced by parents on diapause induction in Trichogramma cacoeciae

In the genus Trichogramma, the prepupal stage can survive the cold season in diapause. However, optimal conditions for the induction of this cessation of development during the process of mass production of the parasitoid in a biological control program depend on the species. In Trichogramma cacoeciae Marchal (Hymenoptera: Trichogrammatidae), diapause is induced more easily if the parents are reared under short‐day conditions (L10:D14), and if the temperature is 10 °C rather than 13 °C. However, the effect of parental photoperiod on diapause induction is weaker at lower temperatures (10 °C). Following diapause induction, individuals can be stored at 3 °C for several months, up to 1 year. Non‐optimal conditions led to the establishment of a quiescent state in some or all individuals. In such cases, it was necessary to reduce the storage period to 1 or 2 months only, to prevent high mortality rates and low fecundity.     

Emergence of the overwintering generation of peach fruit moth (Carposina sasakii) depends on diapause and spring soil temperatures

Survival rate and emergence timing of the overwintering generation of many temperate agricultural pests is expected to affect their population dynamics and damage potential. However the impact of fluctuating winter and spring conditions on the successful emergence of insects post-diapause is generally poorly known. Here we characterize diapause responses in the peach fruit moth (PFM) pest, Carposina sasakii Matsumura, which overwinters at the larval stage in soil. Temperatures at a depth of 5 cm fluctuated markedly in early spring during the critical PFM post-diapause period (late December to mid-April). By removing outdoor larval samples over this period, we show that the completion of diapause for PFM in northern China starts from late January and continues until March. This extended developmental period is accompanied by an ongoing loss of cold resistance. Temperature conditions experienced in the field were associated with cold tolerance and emergence times, and reduced cold tolerance was associated with shorter emergence time. Cryoprotectants declined from late December, and levels were associated with changes in the supercooling point (SCP) of the larvae, but both correlated weakly to survival under cold stress during the post-diapause period. These findings suggest that diapause stage and soil temperatures should be taken into account when predicting field dynamics of soil-dwelling overwintering insects based on degree day accumulation models and other approaches.     

Effects of thermoperiod on photoperiodic determination of larval diapause in Ostrinia nubilalis

Some effects of thermoperiods on the photoperiodic determination of larval diapause in the European corn borer, Ostrinia nubilalis are reported. Thermoperiods and photoperiods were shown to interact to a highly significant degree in the induction of diapause. Diapause determination was found to be sensitive to the duration and temperature of the cryoscotophase of the thermophotoperiod; the thermophotophase characteristics exerted only minor influence. Cryoscotophase temperatures of 10°C or lower caused an unexpected increase in the apparent critical nightlength for diapause determination. A 0°C cryoscotophase effectively prevented the photoperiodic determination of diapause. Experimental investigation of the effects of 0°C cryoscotophases produced evidence that such low-temperature cryoscotophases may suppress the biological clock functions regulating the determination of diapause. Photoperiodic regimes in which 0°C pulses were inserted at successive points in 24-h cycle evoked responses suggesting that the early scotophase (saturation phase) was more strongly influenced by the low temperature pulse than was the later scotophase (scotonon); low temperature had little effect on the light-dependent processes (photonon) associated with the photophase.