Diapause termination in the spotted stem borer, Chilo partellus (Lepidoptera: Pyralidae) in the laboratory

The effect of temperature, photoperiod, artificial diet and water on the termination of diapause by larvae of the stem borer, Chilo partellus (Lepidoptera: Pyralidae), was studied in the laboratory. Termination of diapause as indicated by pupation was affected mainly by a combination of high temperature and a long day photoperiod. Total darkness did not prevent termination of diapause and pupation occurred also in larvae which were never exposed to water. Long days accelerated pupation, but, under 16 h daylength, termination of diapause was faster than under constant illumination. Provision of artificial diet had no effect or slowed down pupation but water decreased the time to pupation. Under 28°C, 16 h daylength and availability of water, C. partellus diapausing larvae terminated diapause and pupated in about 9 days.     

Effect of the presence of olive fruit on ovarian maturation in the olive fruit fly, Dacus oleae, under laboratory conditions

Ovarian maturation was prevented in 7-, 22-, 23- and 28-day-old females of Dacus oleae (Gmelin) (Diptera: Tephritidae), developed in the pre-imaginal stages at LD 12:12, 19±1°C and kept as adults at LD 16:8, 26±1°C without access to olive fruits. In females of the above ages having continuous access to olive fruits and held under the same photoperiod and temperature conditions, 54, 87 and 100%, respectively, had mature oocytes. When the females had access to domes of paraffin wax, the percentages of females with mature oocytes were intermediate between those with and those without access to olive fruits. Under the above photoperiod and temperature conditions unfavorable for maturation, 50% of 4-week-old females had mature oocytes if exposed for one week to olive fruits during their first week and 91% if exposed during their 4th week of adult life. The respective percentages with wax domes in the cages were again intermediate between those with olives and those without olives or wax domes. The presence of olive fruits had also a strong positive effect on the ovarian maturation of females which developed from egg through the adult stage at LD 16:8, 26±1°C, a condition favoring ovarian maturation. Access to wax domes had again an intermediate effect on maturation. It is concluded therefore that the lack of ovarian maturation of D. oleae females which is observed under a short photophase during the pre-imaginal stages if followed by a long photophase and an increase of temperature during the adult stage, continues at least till the end of the 4th week of adult life in the absence of olive fruits but is averted when such fruits are offered to the adult flies.

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Résumé La maturation ovarienne des femelles adultes agées de 7, 22–23 et 28 jours de D. oleae ayant accompli leur développement embryonnaire, larvaire et nymphal en LD 12:12, 19±1°C et maintenues en LD 16:8, 26±1°C, sans accès à des olives, est inhibée. Dans les mêmes conditions, mais avec accès permanent à des olives, 54% des femelles ont des ovocytes mûrs à 7 jours, 87% à 22–23 jours et 100% à 28 jours. Avec des femelles ayant accès à des domes de paraffine, les pourcentages d'individus ayant des ovocytes mûrs sont intermédiaires entre ceux des deux situations précédentes. Dans les conditions cidessus défavorables à la maturation ovarienne, 50% des femelles de 28 jours ont des ovocytes mûrs si elles sont en présence d'olives durant leur première semaine de vie imaginale et 91% si elles sont en présence la 4éme semaine. Les pourcentages respectifs concernant les femelles pourvues de dômes de paraffine sont encore intermédiaires entre ceux des femelles avec olives et ceux de femelles privées de tout substrat. La présence d'olives a aussi un effet fortement positif sur la maturation ovarienne de femelles ayant accompli leur développement pre-imaginal et maintenues aussi à l'etat adulte en conditions LD 16:8, 26±1°C, favorisant la maturation ovarienne. L'accès à des dômes de paraffine a, là encore, un effet intermédiaire. On conclut par conséquent que la non maturation ovarienne des femelles de D. oleae qui est causée par une photopériode à jour court pendant la vie pre-imaginale accompagné par une photopériode à jour long et une augmentation de la température pendant la vie imaginale persiste au moins jusqu'à la fin de la quatrième semaine de la vie imaginale en absence d'olives, mais ne se produit pas si on met les femelles adultes en présence d'olives.

     

Maintenance and termination of reproductive dormancy in an Australian stink bug, Biprorulus bibax

Reproductive dormancy in female Biprorulus bibax Breddin sampled during March-October in Southern New South Wales was terminated by exposure to 25°C under long (15h) and short (10h) photoperiods. 27% of individuals collected during March-May failed to oviposit under short days. Pre-oviposition period under short photoperiod was greates during March-June (22.4–61.7 d) and shortest during July-October (4.2–14.4 d). Under long photoperiod it was greatest in April and May (20.1–22.3 d) and shortest during June-October (4.9–16.6 d). Longevity ranged from 39.8–89.0 d, with longest lived females being collected in June and held under short days. Fecundity ranged from 51.6–164.4 and was greatest in individuals collected in June-July and held under short days. In females held under long days fecundity was greatest in March and lowest in May. These data indicate that female B. bibax pass the winter in a photoperiodically maintained reproductive diapause.     

Diapause termination and egg hatch in the bird cherry aphid, Rhopalosiphum padi

Conclusion TastePROBE is a convenient and flexible electronic circuit designed to record action potentials from taste sensilla of insects. It facilitates the recording of slow potentials arising in taste sensilla, improves the signal to noise ratio, and preserves spike shapes. This new amplifier design combines excellent signal to noise ratio with complete compatibility as regards existing electrophysiological equipment.DC recordings have higher information content than filtered recordings. With DC recordings, spike shapes are not modified and thus better sorting is possible. Moreover, slow variations in the transepithelial potential (i.e. less than 10 Hz) are preserved. Both aspects are of considerable importance when studying the physiology of taste receptors.     

Diapause induction in the codling moth, Cydia pomonella: effect of prediapause temperatures

The effect of four prediapause temperatures (18, 22, 26 and 30°C) on the photoperiodic response of the codling moth, Cydia pomonella (L.), was studied under controlled conditions. The highest rates of diapause were recorded, for all day-lengths, at temperatures of 22 and 26°C while relatively lower rates of diapause were elicited at 18 and 30°C. The same trend was demonstrated by projecting the values of the critical photoperiod which induces 50% diapause (=CPhP₅₀) over the prediapause temperature. The change in diapause incidence as a function of photoperiod, at all prediapause temperatures, exhibited a response characteristic of long-day insects, i.e. high rates of diapause at short days (12–13.5 h) and a decrease in diapause incidence at long days (14–15 h). The results for temperatures 22, 26 and 30°C support the view that lower prediapause temperatures enhance diapause induction, at a give photoperiod, while higher temperatures tend to avert or diminish the process. On the other hand, the low rates of diapause obtained at 18°C contradict this view. Nevertheless, high correlation was found between the laboratory evidence and field data, indicating the adaptability of the Israeli codling moth to subtropical climate.     

Diapause and seasonal life cycle strategy in the house spider, Achaearanea tepidariorum (Araneae, Theridiidae)

Abstract In order to elucidate the mechanism regulating its seasonal life cycle, the photoperiodic response of Achaearanea tepidariorum has been analysed. Nymphal development was faster in long-day and slower in short-day photoperiods. The combined action of low temperature, poor food supply and short daylength induced diapause at an earlier developmental stage than short days alone. Thus, photoperiod is a primary factor inducing nymphal diapause, but the diapausing instar is influenced by both temperature and food supply. Hibernating nymphs became unresponsive to photoperiod in late December. After hibernation, however, sensitivity was restored and the nymphs remained sensitive to photoperiod throughout their life. This spider could also enter an imaginal or reproductive diapause. Photoperiod was again a primary inducing factor and temperature modified the photoperiodic response to some extent. The induction of the reproductive diapause was almost temperature-compensated whereas development was not. So the involvement of a photoperiodic counter system was suggested. Irrespective of whether the nymph had experienced diapause or not, the imaginal diapause was induced in response to a short-day photoperiod after adult moult. Based on these observations, the seasonal life cycle and the adaptive significance of nymphal and imaginal diapause are discussed.     

Diapause induction in the codling moth, Cydia pomonella: effect of larval diet

The effect of larval diet on diapause induction in the Israeli strain of the codling moth, Cydia pomonella (L.), was studied in a field trial using intact apple fruits of two varieties: Ana (early-ripening, in the end of June) and Granny Smith (late-ripening, in October). Diapause incidence increased as fruit age (determined as days from fruit-set) progressed. These results corroborate former studies on other strains of the codling moth, where excised fruits were used.The combination of 80-day-old, fully ripe, Ana fruit treatment with the longest days of the year, yielded 38% diapause. This result demonstrates that mature fruit (inducing diapause) cannot completely override the effect of long day (averting diapause), but does confirm that larval diet modifies the photoperiodic induction of diapause in the codling moth.Deceased, October 1988     

Effects of photoperiod and temperature on the termination of diapause in the univoltine seed wasp Eurytoma plotnikovi

Abstract Mummified pistachios containing fully grown diapause larvae of Eurytoma plotnikovi Nikol'skaya (Hym., Eurytomidae) were collected in early August and late September in coastal northern Greece and subjected to various photoperiod and temperature treatments, then maintained at 19 or 26°C and a long-day (LD 16:8 h), a changing, or a short-day (LD 10:14 h) photoperiod until pupation. In larvae of early August (beginning of diapause) subjected for 20 weeks to 19°C under a long, a changing, or a short photophase, followed by 19°C and a long photophase, 50% of the larvae pupated after 24, 18 and 13 weeks respectively. After exposure for 20 or even 12 weeks to a short photophase and low temperatures (10 or 4°C), pupation occurred after only 7–8 weeks and was more synchronous. The ranges of temperature for diapause development and post-diapause morphogenesis overlap. After exposure for 12 weeks to short days and low temperature, larvae of late September pupated much sooner under long days than under short days and sooner at 26° than at 19°C. E.plotnikovi depends on both temperature and photoperiod for diapause development, low temperature having a strong favourable effect on the earlier part and long day on the later part of diapause. In a few larvae of another pistachio seed wasp, Megastigmus pistaciae Walker, after a long enough period of low temperatures, diapause was terminated normally at 26°C and long days, or at 19°C and long or short days.     

Diapause induction and termination in the predatory mite Euseius finlandicus in peach orchards in northern Greece

The course of diapause induction as well as of diapause termination infemales of the predatory mite Euseius (Amblyseius)finlandicus Oudemans (Acari: Phytoseiidae) in Northern Greece wasdetermined by transferring females during winter and early spring from peachtrees to a short day (LD 8:16) or a long day (LD 16:8) photoperiod both at 20°C. The first diapause females were found in mid September andby the first week of October all the females were in diapause. The mean numberof days required for diapause termination under the short day photoperiod LD8:16 was gradually reduced from 93.7 days in the beginning of October to lessthan 20 days in mid February and early March. Under the long day photoperiod ofLD 16:8 diapause was terminated in less than 20 days irrespective of the dateof collection. These results indicate that by mid February photoperiodicsensitivity of females was lost and diapause was terminated. However, femaleswere found in their overwintering sites until the second half of March,probablybecause of the prevailing relatively low temperatures and lack of adequatefood.     

Effect of temperature on the termination of diapause in the univoltine almond seed wasp Eurytoma amygdali

Diapausing larvae of Eurytoma amygdali Enderlein (Hymenoptera, Eurytomidae) were collected in early August and late September. They were subjected to various photoperiod and temperature regimens for up to 20 weeks, then kept at L16:D8 and 19 °C for another 14 to 26 weeks for diapause to be terminated and pupation to take place. Photoperiod did not affect diapause completion. It was confirmed that the two morphologically distinct diapause stages have different temperature requirements for their completion. The first diapause stage was completed synchronously at temperatures between 16 and 19 °C. A higher temperature of 26 °C delayed diapause development. The second stage required lower temperatures between 4 and 10 °C. Spontaneous termination of diapause was observed at constant 19 °C. When applied to the first diapause stage for 20 weeks, low temperatures made the larvae refractory to subsequent intermediate temperatures. The first stage was thus maintained until a higher temperature of 26 °C made the larvae regain their ability to respond to the intermediate temperatures and complete this stage. Larvae grown in Retsou almonds had a higher diapause intensity than larvae grown in Truoito almonds. The results suggest that, in nature, the high temperatures of late summer and early autumn are likely to maintain the first diapause stage. Subsequently, the less warm temperatures of autumn allow the completion of the first stage by late autumn, and the low temperatures of late autumn and of winter allow the completion of the second diapause stage by mid winter.     

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.     

Photoperiodic induction of larval diapause and temperature-dependent termination in a wild multivoltine bruchid,Kytorhinus sharpianus

A wild bean weevil,Kytorhinus sharpianus Bridwell (Coleoptera: Bruchidae), has a multivoltine life cycle and enters a hibernal larval diapause at the fourth instar under a short daylength (Shimada & Ishihara, 1991). Here, we investigated their diapause incidence under different photoperiods at 24°C and 27°C. The critical photoperiods for diapause induction were 14.5 h at 24°C and 14 h at 27°C. The stages susceptible to diapause-inducing stimuli were estimated by transferring larvae of various instars from long days to short days and vice versa. Then we investigated the incidence of larval diapause. The sensitive stage was estimated to be from the third to early fourth instar. Though larval diapause, which was induced under a short daylength, was terminated only by increasing the daylength, the termination was more synchronized by an exposure to a low temperature followed by increasing temperature, irrespective of photoperiod.     

Effects of diet, photoperiod and temperature on the postdiapause reproduction in the cabbage bug,Eurydema rugosa

InEurydema rugosa Motschulsky (Heteroptera: Pentatomidae), the type of food supplied (i.e. seeds or leaves of the brown mustard,Brassica juncea Hemsel) and photoperiod, which control the induction of adult diapause, do not play a role in the initiation of reproduction after overwintering. A temperature above 13.2°C was required to start reproduction. After its initiation, however, short-day conditions on seeds induced diapause again in some adults. Although a diet of seeds under long-day conditions, in common with short-day conditions, induced diapause in young adults (Numata & Yamamoto, 1990), it did not reinduce diapause in adults after overwintering. Thus,E. rugosa that had overwintered became sensitive to diapause-inducing photoperiod again but not to dietary factors.     

Diapause induction in Ephestia cautella: An interaction between genotype and crowding

Larval diapause induction in Ephestia cautella (Walker) (Lepidoptera: Pyralidae) is a function of the interaction between genotype and larval crowding. A diapause stock in which 79% of the larvae diapaused under crowded conditions and 40% diapaused under uncrowded conditions was maintained by selection. Outbreeding of adults from this diapause stock to those from a non-diapause stock resulted in 36% diapause under crowded conditions and 6% diapause under uncrowded conditions. The rate of termination of larval diapause is inheritable and temperature dependent. These data seem to explain the seasonal trends in percentage larval diapause among E. cautella infesting citrus pulp during storage.Larval diapause was induced in groups of larvae by crowding in mass cultures and in single larvae by rearing on a small amount of fresh diet or on a larger amount of fresh diet containing residual diet from crowded cultures. The diapause-inducing effects of this residual diet could be removed by extraction with lipid solvents. Some activity was demonstrated when the extract was dried onto fresh diet.

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Resume L'induction de la diapause larvaire d'Ephestia cautella (Walker) dépend du génotype et de la densité larvaire.Des croisements à l'intérieur de la souche diapausante donnent 79% de diapause aux fortes densités larvaires et 40% aux faibles densités. Les croisements des adultes de cette souche avec ceux de la souche non-diapausante donnent 36% de diapause aux fortes densités et 6% aux faibles densités. La fréquence de fin de diapause est héréditaire et dépend de la température. Ces résultats peuvent expliquer les variations saisonnières du taux de diapause E. cautella dans la pulpe de citron stockée.La diapause larvaire a été induite chez des groupes de chenilles par surpeuplement dans des élevages standards, et chez des chenilles isolées par élevage sur une quantité limitée d'aliments frais ou sur une quantité abondante d'aliments frais contenant des résidus alimentaires provenent d'élevages surpeuplés. Les effets inducteurs de ces résidus alimentaires disparaissent après extraction avec les solvants de lipides. Une certaine action est observée par de l'extraint sec sur de l'aliment frais.

     

大猿叶虫哈尔滨种群的滞育诱导研究

本文研究了光周期、温度和食料对大猿叶虫Colaphellus bowringi Baly哈尔滨种群滞育诱导的影响。结果表明,在恒温20～30℃范围内,大猿叶虫哈尔滨种群滞育率为91.8%～100%,未见明显的光周期诱导反应,但温度对其滞育诱导具有一定的作用,高温可使少部分大猿叶虫继续发育而不滞育。在平均25℃的温周期与光周期L12∶D12条件下,其滞育诱导差异不显著。大猿叶虫取食白菜、油菜、雪里蕻、萝卜和独荇菜5种食料,在25℃滞育率为89.5%～100%;在28℃滞育率为76.9%～100%,食料种类对大猿叶虫哈尔滨种群滞育诱导差异显著,其中,取食独荇菜滞育率最低,取食萝卜滞育率最高。     

Aestivo-hibernal reproductive diapause in Drosophila moriwakii: flight as a controlling factor

Drosophila moriwakii Okada & Kurokawa (Diptera; Drosophilidae) generally has only one generation per year and enters aestivo-hibernal reproductive diapause in Sapporo, northern Japan, but a small fraction of the population produced a second generation in summer at a place where breeding resources were abundant. In this species, diapause seems to be controlled by flight activity. When flies were cultured in cages in which they were able to fly freely, they entered diapause irrespective of photoperiod, but they did not do so at long daylengths when cultured in small vials in which they were prevented from flying. Furthermore, flies with wings removed did not enter diapause at long daylengths even if they were cultured in the cages.     

Diapause, embryo growth and supercooling capacity of Epirrita autumnata eggs from northern Fennoscandia

The supercooling point (SCP) of individual Epirrita autumnata eggs (approx. 60 eggs batch^-1) was tested each month from September (eggs newly laid) to April under laboratory conditions simulating winter temperatures in the field (from +4 to-30 °C). Parallel to each test, one batch of eggs was transferred from the acclimation treatment to room temperature (22 °C) and the incubation duration to the first 50% hatch was recorded, giving a measure of embryo growth at the time of the SCP test. Data also give information on egg mortality, which generally was low.The SCP was found to be equivalent to the lower lethal temperatures for this species. Already in autumn, the SCP was in a low range of-34.9 to-36.5 °C and either rose (at a storage temperature of -3 °C) to a range between-28.3 and-29.8 °C in February, due to reduced cold hardiness during embryogenesis, or remained unchanged because the eggs were in quiescence (at -10 °C).The time to 50% hatch at 22 °C decreased from 60 days to 10–14 days in January when it either continued to decrease up to hatch (at -3 °C), or remained unchanged, indicating end of diapause in January. In December, 260 degree-days (DD) above a threshold of +5.8 °C was required for 50% hatch; in February the corresponding figures were 362 DD and-2 °C.When the supercooling point moved from the low to the high SCP range, the frequency distribution of the individual SCPs changed from positively to negatively skewed. The transition was rapid, intermediary distributions being flat and covering both ranges.Thus, in the field the eggs run the risk of freezing mainly at two temperature levels: below about-36 °C during diapause and post-diapause quiescence (in midwinter) and below about-29 °C during embryogenesis (in late winter spring).

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Résumé La température de congélation (supercooling point: SCP) de chaque uf de E. (Oporinia) autumnata (Lépido, géométride) (environ 60 ufs par ponte) a été examinée chaque mois, de septembre (ufs venant d'être pondus) à avril, dans des conditions simulant les températures hivernales de la nature (de-30° à +4 °C). Parallèlement à chaque expérience, une ponte était transférée aux fins d'acclimatation à la température du laboratoire (22 °C) pour noter la durée d'incubation des premiers 50% d'ufs éclos, afin d'avoir une donnée sur la durée du développement embryonnaire à l'époque de l'expérience de congélation, et sur la mortalité embryonnaire, d'ailleurs généralement basse.Le point de congélation (SCP) a correspondu pour cette espèce aux températures létales les plus basses. En automne déjà, la SCP avait une gamme basse de-34.9 à-36.5 °C et, soit s'élevait (pour une température de conservation >-3 °C) à une gamme de-28.3 à-29.8 °C en février, par suite de la diminution de la résistance au froid pendant l'embryogenèse, soit demeurait inchangée parce que les ufs étaient quiescents (<10 °C).Le temps d'éclosion 50 à 22 °C s'est abaissée de 60 j à 10–14 j en janvier pour ensuite, soit continuer de diminuer jusqu'à l'éclosion (>-3 °C), soit rester inchangé indiquant la fin de la diapause en janvier. En décembre, 260 degrés-jours (DD) au-dessus du seuil de +5.8 °C ont été nécessaires pour obtenir 50% d'éclosions, en février il a fallu 362 DD et-2 °C.Quand la température de congélation était déplacée de faibles à fortes valeurs de la SCP, la distribution des fréquences des SCP individuelles passait d'un biais positif à un biais négatif. La transition était rapide, les distributions intermédiaires étant plates et recouvrant les deux gammes.Ainsi les risques de congélation des ufs dans la nature se situent à deux niveaux: environ audessous de-36 °C pendant la diapause et la quiescence post-diapause (au milieu de l'hiver), et au-dessous d'environ-29 °C pendant l'embryogenèse (en fin d'hiver et au printemps).

     

Diapause induction, maintenance and termination in the rice stem borer Chilo suppressalis (Walker)

The rice stem borer, Chilo suppressalis, enters facultative diapause as fully grown larvae in response to short-day conditions during the autumn. Our results showed that the critical night length for diapause induction in C. suppressalis was between 10 h 22 min and 10 h 45 min at 22, 25 and 28 °C, 11 h 18 min at 31 °C, and between 10 h 5 min and 10 h 20 min under field conditions (average temperature ranged from 27.2 to 30.7 °C). The diapause incidence declined in ultra-long nights (18-22 h scotophases) and DD, and increased in ultra-short nights (2-6 h scotophases) and LL. Moreover, we found that the third instar was the stage most sensitive to the photoperiod, and night length played an essential role in the initiation of diapause. Night-interruption experiments with a 1-h light pulse at LD 12:12 (light 12:dark 12) exhibited two troughs of diapause inhibition, with one occurring in early scotophase and the other in late scotophase. Field observations for six years showed that most larvae entered winter diapause in August in response to declining day lengths, despite the high temperatures prevailing during August. By periodically transferring the field-collected overwintering larvae to different photoperiods and temperatures, the results showed that photoperiod had a significant influence on diapause development during the early phase of diapause, while high temperature significantly accelerated the termination of larval diapause.