Life-History Variation inChrysoperla carnea:Implications for Rearing and Storing a Mexican Population

A population ofChrysoperla carneafrom San Pedro, Coahuila, Mexico, showed phenological responses that differ from those of previously studied North American biotypes. Short daylengths that induce diapause in other biotypes resulted in low incidences of diapause in the San Pedro population. Diapause induction required a decrease in daylength (from long to short days). Constant long days produced variable reproductive responses, whereas an increase in daylength (from short to long day) resulted in high incidences of reproduction. Providing prey to adults that had been reared under short days consistently increased the incidences of reproduction. Storage of either diapausing or nondiapausing adults at low temperature (5°C) for 13 weeks yielded better survivorship and reproductive performance than in unstored (24°C) controls. For efficient production, the San Pedro population ofC. carneamay be reared either with an increase in daylength or with the regular intervention of a storage period. To induce diapause in individuals destined for storage, larvae may be reared under long-day photoperiod and the prepupae transferred to short days.     

Geographic variation in diapause induction and termination of the cotton bollworm, Helicoverpa armigera Hübner (Lepidoptera: Noctuidae)

Overwintering diapause in Helicoverpa armigera, a multivoltine species, is controlled by response to photoperiod and temperature. Photoperiodic responses from 5 different geographical populations showed that the variation in critical photoperiod for diapause induction was positively related to the latitudinal origin of the populations at 20, 22 and 25 °C. Diapause response to photoperiod and temperature was quite different between northern and southern populations, being highly sensitive to photoperiod in northern populations and temperature dependence in southern populations. Diapause pupae from southern population showed a significantly shorter diapause duration than from northern-most populations when they were cultured at 20, 22, 25, 28 and 31 °C; by contrast, overwintering pupae from southern populations emerged significantly later than from northern populations when they were maintained in natural conditions, showing a clinal latitudinal variation in diapause termination. Diapause-inducing temperature had a significant effect on diapause duration, but with a significant difference between southern and northern populations. The higher rearing temperature of 22 °C evoked a more intense diapause than did 20 °C in northern populations; but a less intense diapause in southern population. Cold exposure (chilling) is not necessary to break the pupal diapause. The higher the temperature, the quicker the diapause terminated. Response of diapause termination to chilling showed that northern populations were more sensitive to chilling than southern population.     

Induction and termination of diapause inOrius predatory bugs

Photoperiodic induction of reproductive diapause at 18°C was investigated in fourOrius [Heteroptera: Anthocoridae] species.Orius insidiosus (Say) displayed a long-day response with a critical photoperiod between L11:D13 and L12:D12. Diapause in this species was terminated rapidly when the temperature and/or the daylength were increased.Orius majusculus (Reuter) also displayed a long-day response. The critical photoperiod fell between L14:D10 and L16:D8. Diapause in this species was not terminated within 14 days when both temperature and daylength were increased. InOrius albidipennis (Reuter) no diapause could be induced at photoperiods varying from L8:D16 to L16:D8. InOrius tristicolor (White) a high proportion of diapause was found at all photoperiods tested. The effect of temperature on photoperiodic induction of diapause was studied inO. insidiosus at L10:D14. Diapause occurred at 18°C, 21°C and 25°C, but not at 30°C. Again, diapause was terminated rapidly after transfer to 25°C/L16:D8. Exposing only the nymphal instars 1–5 to short daylength was not enough to induce diapause in the whole population ofO. majusculus. Orius predatory bugs are used as biocontrol agents against western flower thrips,Frankliniella occidentalis (Pergande) [Thysanoptera: Thripidael, in greenhouses. The consequences of photoperiodic induction of diapause for the success of early season releases ofOrius are discussed.     

Diapause‐inducing signals prolong nymphal development in the two‐spotted spider mite Tetranychus urticae

Female two‐spotted spider mite Tetranychus urticae are grown under different photoperiods and the photoperiodic regulation of diapause is examined. The photoperiodic response curve for diapause induction was of the long day–short day type, with critical day lengths (CDLs) of 2 and 12.5 h; diapause was induced between these CDLs. The preimaginal period is significantly longer in diapausing females than in non‐diapausing females; moreover, a significant positive correlation is detected between diapause incidence and deutonymphal period. Diapause incidence is high when long‐night photoperiods are applied against a background of continuous darkness in the stages including the deutonymph; this stage appears to be the most sensitive to photoperiod. These observations suggest that diapause‐inducing conditions inhibit nymphal development, particularly in the deutonymphal stage when photoperiodic time measurement for determination of reproduction or diapause is carried out.     

Seasonal variation in the photoperiodic responses of a pea aphid population: evidence for long-distance movements between populations

Summary The purpose of the study was to quantify long distance movements in populations of pea aphid, Acyrthosiphon pisum (Harris), by estimating origins and distances travelled by immigrants into a southern Manitoba population. A strong relationship was demonstrated between latitude of origin and photoperiods at which pea aphid populations are stimulated to produce the diapause stage (Smith 1987). Therefore, the approach was to use photoperiodic response as a physiological marker to identify the source of immigrant aphids. The responses of 89 clones from Glenlea, Manitoba (49°38N), sampled 5 times over 2 seasons, were measured. One sample of clones collected the first season had photoperiodic responses similar to those of a population about 300 km to the south, and significantly different from clones collected in spring of the same year at the same site. Weather analysis corroberates that the migrants were probably carried into Manitoba on a southerly flow of air during the previous 24 to 36 h.     

Photoperiodic induction of prepupal diapause and its role in synchronization with host phenology in the hibiscus caterpillar,Xanthodes transversa

The hibiscus caterpillar, Xanthodes transversa (Lepidoptera: Noctuidae), is a multivoltine insect that is an important pest of Malvaceae plants such as the okra, Abelmoschus esculentus, and the common rose mallow, Hibiscus mutabilis, in Japan. In the present study, the effects of photoperiod and temperature on the induction of prepupal diapause and the adaptive significance of this diapause were examined in a local population of X. transversa in Miyazaki, Kyushu, southwestern Japan. Larvae showed a long‐day photoperiodic response for controlling the induction of prepupal diapause with a critical day length between 13 and 14 h at 20 to 25°C. Under long‐day conditions larvae rapidly pupated from the sixth instar, but under short‐day conditions they entered diapause in the prepupal stage. Diapause occurrence in the field increased in late September, which was consistent with the laboratory results in terms of the photoperiodic response. Non‐diapause development after this time is maladaptive because most larvae of the next generation could not reach the critical stage (prepupae) before winter and died during early winter in outdoor experiments. Larvae suffered from a high rate of mortality when fed leaves collected late in autumn. The photoperiodic response for controlling the induction of diapause in this insect may play an important role in synchronizing the life cycle with the seasonal changes in food and temperature conditions.     

Latitudinal clines in the timing and temperature-sensitivity of photoperiodic reproductive diapause in Drosophila montana

Reproductive diapause is a primary mechanism used by arthropods to synchronize their life cycle with seasonal changes in temperate regions. Our study species, Drosophila montana, represents the northern insect species where flies enter reproductive diapause under short day conditions and where the precise timing of diapause is crucial for both survival and offspring production. We have studied clinal variation in the critical day length for female diapause induction (CDL) and their overall susceptibility to enter diapause (diapause incidence), as well as the temperature sensitivity of these traits. The study was performed using multiple strains from four latitudinal clines of the species – short clines in Finland and Alaska and long clines in the Rocky Mountains and the western coast of North America – and from one population in Kamchatka, Russia. CDL showed strong latitudinal clines on both continents, decreasing by one hour per five degrees decline in latitude, on average. CDL also decreased in all populations along with an increase in fly rearing temperature postponing the diapause to later calendar time, the effects of temperature being stronger in southern than in northern population. Female diapause incidence was close to 100% under short day/low temperature conditions in all populations, but decreased below 50% even under short days in 19°C in the southern North American western coast populations and in 22°C in most populations. Comparing a diversity of climatic data for the studied populations showed that while CDL is under a tight photoperiodic regulation linked with latitude, its length depends also on climatic factors determining the growing season length. Overall, the study deepens our understanding of how spatial and environmental parameters affect the seasonal timing of an important biological event, reproductive diapause and helps to estimate the evolutionary potential of insect populations to survive in changing climatic conditions.     

Photoperiodic response in the subtropical and warm‐temperate zone populations of the southern green stink bug Nezara viridula: why does it not fit the common latitudinal trend?

The photoperiodic response of diapause induction is studied in females of five subtropical and warm‐temperate zone populations of Nezara viridula (L.) (Heteroptera: Pentatomidae) in Japan (26.4–34.7°N; 127.4–135.7°E). Laboratory tests at 25 °C demonstrate that both warm‐temperate and subtropical populations have pronounced photoperiodic responses of adult diapause induction. Under short‐day conditions (LD 10 : 14 h), 73–100% of females enter diapause, whereas, under long‐day conditions (LD 15 : 9 h), 87–100% of females are nondiapause and reproduce. When the critical photoperiod for diapause induction is plotted against the latitude of origin of each population, the data points do not show the expected tendency of increasing critical photoperiod northwards but, instead, vary between 12 h 15 min and 13 h 30 min. It is suggested that adults from different populations of such a highly migratory species move often among subtropical islands (by themselves or being assisted by typhoons), thus constantly destabilizing the photoperiodic responses. Although important for general synchronization of seasonal development in the tropics and subtropics, winter diapause might not be so critical for survival in mild winters in these zones. Such circumstances might make the selective pressure over the photoperiodic response less severe in the tropics and subtropics than in the temperate zone. It is suggested that the current climate warming might contribute to this situation as well by promoting polewards migrations and lessening the selective pressure of overwintering conditions.     

Control mechanisms of larval diapause and quiescence in Trogus mactator, an endoparasite of papilionids

First instar larvae of Trogus mactator Tosquinet (Hymenoptera: Ichneumonidae) developed to second instar immediately after pupation of the host, Papilio xuthus L., under a short photoperiod (L10: D14) as well as under a long photoperiod (L15: D9). The host went into diapause as pupa under short photoperiods, and the parasite at the third instar in the host pupa. They responded independently to short photoperiods. The critical photoperiods for diapause induction both in the parasite and the host were between 12 and 13 h, but there was a slight disparity between them. Diapause of neither the parasite nor the parasitized host was terminated under short photoperiods. Diapause of the parasite in a diapausing host pupa was completed when it was transferred to an incubator having a long photoperiod. This suggests that the exposure to a long photoperiod breaks diapause in the parasite irrespective of physiological conditions of the host. The period from the change in photoperiod to time of parasite emergence shortened as the change was made later. The parasite remaining in a host pupa for 60 days completed diapause even under a short photoperiod when it was implanted into a nondiapausing host pupa, or when 20-hydroxyecdysone was injected into the parasitized and diapausing host pupa. These results indicate that the physiological development for diapause termination in T. mactator seems to complete 60 days after host pupation and endogenous ecdysteroids are somehow involved in termination of diapause in the parasite.

---

Résumé Que la photopériode soit brève (L10/D14) ou longue (L15/D9), le premier stade de T. mactator Tosquinet (Hym. Ichneumonidae) donne un second stade immédiatement après la nymphose de son hôte, Papilio xuthus L.,. L'hôte entre en diapause au stade nymphal sous photopériodes courtest et le parasite au troisiéme stade larvaire dans la nymphe de l'hôte. Ils réagissent indépendamment aux courtes photopériodes. Les photopériodes critiques pour l'induction de la diapause, tant de l'hôte que du parasite, se situent entre 12 et 13 h, mais il y a une légère différence. Ni la diapause de l'hôte, ni celle du parasite ne se terminent sous de courtes photopériodes. Le transfert dans une étuve ayant une longue photopériode rompt la diapause du parasite dans un hôte diapausant. Ceci laisse supposer que l'exposition à une longue photopériode rompt la diapause du parasite quel que soit l'état physiologique de l'hôte. Le délai entre le moment du changement de la photopériode et la date d'émergence du parasite, est d'autant plus raccourci que le changement est tardif. Les parasites restés dans une nymphe hôte pendant 60 jours, achèvent leur diapause même avec une photopériode courte quand ils sont transplantés dans un hôte sans diapause, ou quand de la 20-hydroxyecdysone a été injectée dans la nymphe hôte parasitée et diapausante. Ces résultats montrent que le développement physiologique nécessaire à la fin de la diapause semble achevé 60 jours après la nymphose de l'hôte et que les ecdystéroïdes endogènes semblent impliqués d'une manière ou d'une autre dans la fin de la diapause du parasite.

     

Melatonin pathway transmits information to terminate pupal diapause in the Chinese oak silkmoth Antheraea pernyi and through reciprocated inhibition of dopamine pathway functions as a photoperiodic counter

The present study investigated the functional involvement of melatonin and dopamine in photoperiodism to terminate pupal diapause in the Chinese oak silkmoth, Antheraea pernyi (Lepidoptera: Saturniidae). Diapause in this long‐day (short‐night) species is maintained during long nights and can be terminated by exposure to a short‐night photoperiod. We observed the effects of melatonin and dopamine and their receptor antagonists on diapause pupae. Melatonin and flupentixol, a dopamine receptor antagonist, terminated pupal diapause even under long‐night photoperiods. Dopamine and luzindole, a melatonin receptor antagonist, retarded adult emergence during short nights, whereas melatonin advanced the timing of adult emergence under the short‐night photoperiod in a manner dependent on the number of injections. The results of the day‐length extension experiment indicated that a change in the photoperiod was immediately detected as mRNA expression of the rate‐limiting enzyme of melatonin production. These findings suggest that the melatonin pathway transmits information on the photoperiod to terminate the pupal diapause of A. pernyi. The melatonin pathway also inhibited the dopamine production system, and the dopamine pathway inhibited the melatonin production system. We propose an insect model of the photoperiodic counter driven by mutual inhibition between the melatonin and dopamine pathways.     

Geographic variation in diapause incidence, life-history traits, and climatic adaptation in Drosophila melanogaster

In Drosophila melanogaster, exposure of females to low temperature and shortened photoperiod can induce the expression of reproductive quiescence or diapause. Diapause expression is highly variable within and among natural populations and has significant effects on life-history profiles, including patterns of longevity, fecundity, and stress resistance. We hypothesized that if diapause expression is associated with overwintering mechanisms and adaptation to temperate environments, the frequency of diapause incidence would exhibit a latitudinal cline among natural populations. Because stress resistance and reproductive traits are also clinal in this species, we also examined how patterns of fecundity and longevity varied with geography and how stress resistance and associated traits differed constitutively between diapause and nondiapause lines. Diapause incidence was shown to vary predictably with latitude, ranging from 35% to 90% among natural populations in the eastern United States Survivorship under starvation stress differed between diapause and nondiapause lines; diapause phenotypes were also distinct for total body triglyceride content and the developmental distribution of oocytes in the ovary following stress exposure. Patterns of longevity, fecundity, and ovariole number also varied with geography. The data suggest that, for North American populations, diapause expression is functionally associated with overwintering mechanisms and may be an integral life-history component in natural populations.     

Rhythmic components of photoperiodic time measurement in the pitcher-plant mosquito, Wyeomyia smithii

Photoperiodic time measurement regulating larval diapause in the pitcher-plant mosquito, Wyeomyia smithii, varies in a close relationship with latitude. The critical photoperiod mediating the maintenance and termination of diapause is positively correlated with latitude (r ² = 0.977) among six populations from southern (30–31° N), intermediate (40° N), and northern (46–49° N) latitudes in North America. The developmental response to unnaturally short and to unnaturally long photoperiods declines with increasing latitude, so that longer critical photoperiods are associated with a downward rather than a lateral shift in the photoperiodic response curve. Exotic light and dark cycles of varying period (T) with a short (10 h) photophase and a scotophase ranging from 14 (T = 24) to 62 (T = 72) h, reveal two geographic patterns: a decline in perturbability of the photoperiodic clock with increasing latitude, and no change with latitude in the 21-h period of rising and falling development with increasing T. These results show (1) that there is a rhythmic component to photoperiodic time measurement in W. smithii, (2) that the period of this rhythm is about 21 h in all populations, and (3) that more northern populations show decreasing responsiveness to photoperiod and increasing stability against perturbation by exotic period lengths (T > 24). Previous studies on W.␣smithii indicate that this single temperate species of a tropical and subtropical genus has evolved from south to north. We therefore conclude that the evolution of increasing critical photoperiod in W. smithii during its adaptive radiation into North America has more likely involved the amplitude and not the period of the underlying circadian pacemaker. Received: 22 July 1996 / Accepted: 30 September 1996     

Control of diapause in codling moth larvae

Diapause in a New Zealand strain of codling moth (Cydia pomonella Linnaeus [Lepidoptera: Olethreutidae]) was induced in larvae by photoperiods of 15 h or less. Once diapause had been initiated, it could not be terminated by any combination of conditions tested for at least 20 days after cocooning. In diapausing larvae a low rate of pupation occurred at 25 °C under a long day (18 h) photoperiod. A high rate of pupation was achieved under a long day regime when larvae were decocooned, and provided with apple as nourishment. Diapause could be terminated predictably in 94–100% of larvae by 1) conditioning at 15 °C and constant darkness for periods of 40–100 days, then 2) chilling at 2±2 °C and constant darkness for 20–50 days followed by 3) any post-chill condition periods at 25 °C, 18 h photoperiod. Complete diapause termination was achieved when 100 days conditioning was followed by 30 days or 50 days post-chill period. Under these conditions, 76% termination occurred in the post-chill period after 10 days, and 93% after 25 days.To terminate diapause in codling moth larvae, we recommend that a 100 days conditioning followed by 30 days chilling and 50 days post chilling periods be used.     

Diapause induction in adults of three Rhipicephalus appendiculatus stocks

Newly-moulted adults of three Rhipicephalus appendiculatus stocks, originating from Kenya, Zambia and Zimbabwe, were kept in different photoperiods (12h : 12h, 13h : 11h and 14h : 10h light : dark). The stock originating from Kenya showed almost no behavioural diapause in any of these day lengths, whereas virtually all individuals of the Zimbabwean stock entered a behavioural diapause irrespective of day length. Adults from the Eastern Province of Zambia, a transition zone between the multivoltine phenology in equatorial Africa and the univoltine in southern Africa, exhibited a photoperiod-dependent diapause response. The possible mechanisms of diapause regulation and their origin are discussed.     

Energy storage during reproductive diapause in the Drosophila melanogaster species group

Summary Temperate species of the Drosophila melanogaster group enter reproductive diapause for overwintering in response to short daylength. During the prediapause period they accumulate triacylglycerols, but not glycogen, as energy resources. The capacity for storing triacylglycerols differs between species, and appears to be closely correlated with diapause and cold-hardiness; cool-temperate species, such as those of the auraria species complex, which enter a deep diapause and are highly cold-hardy, accumulate larger quantities of triacylglycerols than warm-temperate species, such as D. rufa and D. lutescens, which enter a weak diapause and are less cold-hardy. Among the cool-temperate spcies, D. subauraria occurs at a higher latitude and has the greatest capacity for accumulating triacylglycerols. A subtropical species, D. takahashii, which has no diapause in nature and is not cold-hardy, is unable to store the same quantities of triacylglycerols as temperate species.     

光周期和温度对亚洲玉米螟滞育诱导的影响

亚洲玉米螟Ostrinia furnacalis (Guenée)属兼性滞育昆虫, 其滞育特性与种群利用适生境的最大化和季节性活动密切相关。解析季节性因素如光周期和温度对其滞育的诱导作用可为预测种群发生动态提供科学依据。本实验在HPS 500型和HPG-320H型自动控制环境气候箱中, 测定了RH 80%下温度20℃, 27℃和30℃与11个光周期组合对吉林农安（NA）、 河北衡水（HS）、 广东惠州（HZ）和海南海口（HK）等4个地理种群的滞育诱导作用。结果表明： 光周期、 温度及其交互作用均对亚洲玉米螟滞育诱导具有重要影响, 其中光周期在滞育诱导中起主导作用。在20℃条件下, 其光周期反应曲线属典型的长日照反应型, 临界光周期随种群分布的地理纬度降低而缩短, 4个地理种群NA, HS, HZ和HK的临界日昼长依次为14 h 3 min, 13 h 59 min, 13 h 32 min和13 h 7 min, 最有效的滞育诱导光周期是日昼长12 h。另一方面, 随种群分布纬度升高, 其对光周期诱导滞育的敏感性降低。温度为27℃时, 其光周期反应曲线为短日照 长日照反应型, 各种群有两个临界光周期, 临界日昼长依次为12 h 50 min和13 h 32 min, 11 h 35 min和13 h 8 min, 12 h 58 min和13 h 1 min, 以及11 h 50 min和12 h 26 min, 且最有效的滞育诱导光周期范围的滞育率明显低于20℃。一定温度范围内（20℃～27℃）, 随温度升高, 临界光周期缩短; 温度达到30℃时则滞育显著被抑制, 滞育率仅为4.3%或更低。这些结果说明温度对亚洲玉米螟滞育的光周期诱导具有很强的补偿作用。因此, 在自然界亚洲玉米螟的滞育属具有温度补偿作用的长日照反应型昆虫, 临界光周期随地理纬度北移而增长; 种群滞育的短日照 长日照反应型特性可能是产生局部世代种群的重要内因。     

Effects of low temperature on diapause termination and body colour change in adults of a stink bug, Plautia stali

Abstract. Diapause adults of Plautia stali Scott maintained at 20°C under short day conditions (LD 12:12 h) were exposed to four temperatures of 5–20°C to examine the effect on diapause development which was assessed in terms of oviposition. Diapause adults kept at 20°C under short day conditions changed their body colour gradually from brown to green and started egg laying after a prolonged preoviposition period. Those transferred to either 10 or 15°C also showed colour change but did not lay eggs. Bugs exposed to 5°C underwent neither body colour change nor oviposition and died more rapidly than those kept at higher temperatures. When 30-day-old diapause adults were chilled at 5, 10 or 15°C for 30 or 60 days and returned to 20°C and long day conditions (LD 16:8 h), the preoviposition period varied primarily depending on the chilling, but not on the temperature. On the other hand, when 60day-old diapause adults chilled for 30 days were observed at 20°C and long day conditions, their preoviposition period tended to be longer as the chilling temperature was lower In this case, a temperature of 10°C appeared to intensify diapause. Therefore, the effect of chilling on diapause development varied depending on the age at which insects were chilled. When chilled bugs were transferred to short day conditions at 20°C, most females failed to lay any eggs and some turned green, then after a while, some green bugs changed to brown again. These results indicate that bugs remained sensitive to short day conditions even after a 60-day chilling at 10 or 15°C.     

中华稻蝗五地理种群的卵滞育强度及生活史模式变异

为调查中华稻蝗Oxya chinensis的地理适应,自北纬42.3°至20.0°采集了5个地理种群的标本,比较了其子代的卵滞育发生、滞育强度及成虫虫体大小。结果表明: 不同的中华稻蝗地理种群显示了不同的光周期和温度反应模式。铁岭、济宁和泗洪种群的滞育不受光周期和温度的影响,滞育率均为100%。南方的长沙和海口种群仅部分卵进入滞育,海口种群在短日条件下的滞育率高于长日条件,卵期温度亦对其滞育有较大的影响,而长沙种群的卵滞育仅受卵期温度的调控。长沙和海口种群的卵滞育强度最弱,其次是铁岭种群,中间纬度的济宁和泗洪种群的滞育强度最高。在北方的一化性种群中,滞育强度随着纬度的降低而增强。成虫的虫体大小因栖息地纬度的变化而呈现复杂的变异,北方种群的虫体大小与栖息地纬度存在显著的负相关关系,而长沙和海口种群的虫体小于济宁和泗洪种群。结果提示中华稻蝗各种群已形成各自的地理适应机制,纬度梯度在其生活史的形成和发育中起着重要的作用。     

Selection for high diapause incidence in blow flies (Calliphora vicina) maintained under long days increases the maternal critical daylength: some consequences for the photoperiodic clock

Using a population of Calliphora vicina from southern Scotland (55 degrees N), showing a critical day length for maternal induction of diapause of about 14.5 h per day, strains of flies were selected for a high incidence of larval diapause under long day length (LD 16:8 h). Diapause incidence was raised from under 10% to almost 100% within five or six generations. The selected flies showed an increase in their critical day length to over 16 h per day, and a high incidence of larval diapause under very long photophases. Selected flies, however, showed mean circadian periods for locomotor activity little different from the original stock, or from flies selected for high diapause under LD 12:12 h, and a Nanda-Hamner profile lacking peaks and troughs of diapause incidence at about 24 h intervals. These results are interpreted to show that the photoperiodic regulation of diapause and the control of overt behavioural rhythmicity are 'separate' physiological systems.