Suppression of female bagworm, Thyridopteryx ephemeraeformis reproduction potential with its sex pheromone, 1-methylbutyl decanoate

Mating of the female bagworm, Thyridopteryx ephemeraeformis (Haworth) (Lepidoptera: Psychidae) on host trees treated with the racemate of the species' female sex pheromone, 1-methylbutyl decanoate, was suppressed by 87% in the field. The suppressive effect of the pheromone was independent of insect population density when it was evaporated from female-infested trees at 712 (±29; S.E.) mg/tree/3 day from a 488 cm × 0.63 cm polyvinylchloride laminated tape. However, evaporation of pheromone at a lower rate did not suppress mating. Observations of adult male behavior in the vicinity of the pheromone-impregnated tape revealed that males were attracted to the tape and that they made copulatory thrusts toward the tape and any object touching the tape. These observations and analyses of the pheromone titers of individual females showed that males can respond to a wide range of pheromone concentrations. Indications are that the mechanism of mating suppression probably involved male sensory adaptation or central nervous habituation to the synthetic 1-methylbutyl decanoate and that the compound, evaporated from host trees, could be useful as a plant protectant against the bagworm.

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Résumé Les accouplements des femelles de Thyridopteryx ephemeraeformis Haworth (Lep. Psychidae) ont été réduits de 87% sur des arbres hôtes traités dans la nature par des racémates du 1-méthylburyldécanoate, la phéromone sexuelle femelle de cette espèce. Lorsque la phéromone s'évapore à partir d'un ruban de 488 cm sur 0,63 de chlorure de polyvinyle portant 712 (±29 S.E.) mg, par arbre pendant 3 jours, l'efficacité était indépendante de la densité de population de l'insecte. Cependant, l'évaporation de la phéromone à une plus faible concentration était sans effet. L'observation du comportement des mâles au voisinage des rubans imprégnés de phéromone a montré qu'ils étaient attirés par le ruban et qu'ils tentaient de s'accoupler avec le ruban et tout objet à son contact. Ces observations et les analyses des concentrations en phéromones des femelles ont montré que les âles pouvaient répondre à une gamme étendue de concentrations en phéromone. Il y a des indices que le mécanisme de suppression de l'accouplement implique une adaptation sensorielle du mâle ou une accoutumance du système nerveux central au 1-méthylbutyl méthylbutyl décanoate synthétique et que ce composé s'évaporant sur les arbres hôtes, pourrait être utilisable pour protéger efficacemment contre T. ephemeraeformis.

     

Differential stratification, movement and parasitism of sexes of the bagworm, Thyridopteryx ephemeraeformis on redcedar

Abstract. 1. Male and female bagworm larvae develop and pupate at different heights on redcedar trees.
2. Habitat segregation by height of male and female bagworms is apparent by the third instar, and results in part from differential movement of male and female larvae on redcedar foliage during their development. Females gradually ascend the crown, whereas males remain at the same height on the tree.
3. Parasitism of male bagworm pupae was greater than for female pupae. Pupal parasitism is heaviest in the bottom of redcedar trees, where most male bagworms pupate.
4. Several hypotheses are offered concerning the origin and maintenance of differential habitat utilization by male and female bagworms, despite apparently strong selection against males pupating low in the crowns of redcedar.     

Aerial dispersal and host plant selection by neonate Thyridopteryx ephemeraeformis (Lepidoptera: Psychidae)

Abstract.  1. Neonate evergreen bagworms, Thyridopteryx ephemeraeformis (Haworth) (Lepidoptera: Psychidae), disperse by dropping on a strand of silk, termed silking , and ballooning on the wind. Larvae construct silken bags with fragments of plant foliage. This species is highly polyphagous, feeding on more than 125 species of woody plants of 45 families. The larvae commonly infests juniper ( Juniperus spp.) and arborvitae ( Thuja spp.), but rarely feed on deciduous hosts such as maples. The hypothesis is proposed that polyphagy in T. ephemeraeformis is maintained by variation among larvae in dispersal behaviour, and time constraints on the opportunity to disperse, but patterns of host species preference result from a predisposition for larvae to settle on arborvitae and juniper but disperse from other hosts.
2. Consistent with that hypothesis, laboratory experiments revealed: (a) starved larvae varied in their tendency to disperse from paper leaf models; (b) starved larvae readily silked only during their first day; (c) larvae became increasingly sedentary the longer they were exposed to plant foliage; (d) when provided with several opportunities to silk, larvae became sedentary after exposure to arborvitae foliage, but repeatedly silked after exposure to maple ( Acer species) foliage or paper; and (e) larvae were less inclined to silk from foliage of arborvitae than from maple.
3. Field experiments supported the hypothesis by demonstrating that: (a) neonates tended to disperse from maple leaves while larvae older than 1 day tended to settle and remain; and (b) neonates were less likely to disperse from arborvitae and juniper trees than from maples.     

Feeding preferences and their modification in early and late instar larvae of the bagworm,Thyridopteryx ephemeraeformis (Lepidoptera: Psychidae)

Feeding preferences in naive first instar and penultimate-final instar bagworm (Thyridopteryx ephemeraeformis)larvae were investigated using two choice tests. Naive first instar larvae showed a general (though not exclusive) preference for black willow (Salix nigra)over other hosts tested, regardless of the host of origin. Penultimate-final instar larvae showed strong preferences for the previous rearing host, suggesting induction of host preference; there was no evidence of host origin effects. The ability to discriminate among hosts is important if it is actually used to make host choices based on host quality. In bagworms, where host choices (if any) must be made by larvae in habitats where several hosts are often present, host discriminatory ability is likely important.     

Sex ratio, pupal parasitism, and predation in two declining populations of the bagworm, Thyridopteryx ephemeraeformis (Haworth) (Lepidoptera: Psychidae)

Abstract. 1. Two populations of bagworms were censused in Ohio for 6 and 5 years respectively, to determine the influence of major pupal mortality factors. Bagworm densities declined from 2.3 bags per 30 cm of terminal branch to zero.
2. No single key mortality factor was identified in population trends. Parasitic Hymenoptera were common but variable in effect. Avian predation may have been important in reducing one population, while the other was exterminated after a drastic change in sex ratio to favour males.     

Diapause termination in two species of damselflies

Larvae of two species of damselflies, Enallagma hageni and E. aspersum, were collected in southwestern North Carolina and subjected to different combinations of daylength (SD, 11 hr day; LD, 14 hr day) and temperature to determine the factor critical in the termination of diapause. Diapausing larvae were collected in September, and 15 comparable groups of each species were given pretreatments (SD, 10°C; LD, 10°C; or SD, 21°C) for 2, 4, or 8 weeks and then transferred to SD, 21°C or LD, 21°C until emergence. Control groups were maintained under both photoperiods at 21°C.Response times (days from collection to emergence) for both species showed that rapid development required transfer to LD, 21°C regardless of the type of pretreatment or length of exposure. Larvae transferred to LD, 21°C after exposure to any of the three types of pretreatment for equal lengths of time developed at similar rates. Pretreatments at 10°C, which were equally effective with SD or LD, stimulated subsequent rapid development at LD, 21°C to a greater extent than continuous exposure to LD, 21°C conditions, and the longer the exposure to 10°C, the faster the subsequent response. Pretreatments at SD, 21°C also resulted in rapid development, similar to that of larvae exposed to 10°C, upon transfer to LD, 21°C conditions. Long daylengths administered only during pretreatments did not effect rapid development, since all larvae responded slowly when transferred to SD, 21°C. Diapause termination, therefore, was effected by LD, 21°C conditions preceded by exposure to either low temperatures, during which the photoperiod was not important, or short daylengths at 21°C.     

Diapause in a Glasgow strain of the flour moth, Ephestia kuehniella

ABSTRACT. The incidence of diapause in Ephestia kuehniella Zeller from an unhealed granary in Scotland was influenced by both photoperiod and temperature. At 25°C, nearly 50% of larvae entered diapause when reared in continuous darkness (DD) and up to 30% did so in short photoperiods. Little diapause was detected around LD 14:10 but a second, smaller peak of about 20% occurred at LD 16:8 and LD 18:6, falling away again to nearly zero in continuous light. More larvae entered diapause when reared continuously at 15 or 20°C than at 25 and 30°C. However, when larvae reared from hatch at 25°C in LD 16:8 were transferred after 1 week to 15°C in LD 9:15, almost twice as many entered diapause as did those reared at 15°C throughout. The sensitive phase for diapause induction occurred near the start of the final instar. The mean duration of diapause was between 2 and 3 months in most photoperiods at 20 and 25°C, and was shorter at 15°C. However, in DD at 25°C, it lasted about 7 months. Termination of diapause was hastened in larvae reared at 25°C in DD by transferring them to LD 14:10, and also by chilling them at 7.5°C for 6 weeks before returning to 25°C in DD. In an unhealed store in southern England, viable adults emerged from May to July and originated from larvae which terminated diapause relatively late. It would appear from the results of transferring larvae back to the laboratory at various times during the winter that some phases of diapause development were completed quite early after exposure to low temperatures, although no further development took place in the store until temperatures rose again in April.     

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 termination in the olive psyllid Euphyllura phillyreae, in the field and in the laboratory

Euphyllura phillyreae Foerster (Homoptera: Aphalaridae) which infests olive trees in Greece, is monovoltine and has an aestival-autumnal-hibernal reproductive dormancy as an adult which starts in June. Adult females collected periodically from June through February were maintained for 4 weeks at 12L:12D and 20° L:18° D, then the stage of ovarian development was recorded.In the field, diapause was terminated between mid December and early January. Subsequently, the insects remain in reproductive quiescence until February or early March when environmental conditions allow ovarian development and reproduction.In females collected in June, summerlike laboratory conditions, followed by winterlike, and then by springlike conditions were effective for diapause termination. Springlike conditions alone, or preceded by only summerlike or only by winterlike conditions were not effective. In females collected in August the requirement for summerlike conditions was much less or nil.

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Résumé Euphyllura phillyreae Foerster qui s'attaque sur l'olivier en Grèce, est une espèce oligophage, monovoltine, qui a une dormance reproductive aestivo-autumno-hivernale au stade adulte, qui commence en juin.Des femelles adultes ont été ramassées par les arbres périodiquement de juin au février et maintenues pendant 4 semaines à 12L:12D et 20° L:18° D. Après cette période, le stade du développement des ovaires a été le critère de la termination de leur diapause. La diapause fut considéré comme terminée quand au moins 50% des femelles avaient leurs ovaires au stade III ou même plus avancées.La diapause fut terminé entre mi-decembre et début janvier. En suite, les insectes restent à une quiescence reproductive jusqu'au février ou début de mars, lorsque les conditions environmentales permettent le développement des ovaires et la reproduction.Des femelles ramassées en juin et en août ont été soumises à certaines conditions de photopériode et de temperature en laboratoire, pour faire terminer leur diapause. Pour celles ramassées en juin, qui étaient au commencement de leur diapause, des conditions semblables à l'été, suivies par des conditions semblables à l'hiver et puis par des conditions semblables au printemps furent effectives pour la termination de la diapause. Seules des conditions semblables au printemps, ou précédées par des conditions semblables seulement à l'été, ou seulement à l'hiver, ne furent pas effectives. Pour les femelles ramassées en août, le besoin pour des conditions semblables à l'été fut beaucoup moin ou nul.

     

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     

Diapause in the gypsy moth: a model of inhibition and development

We present here the first recorded age-specific estimates of the developmental response to temperature in diapausing gypsy moth, Lymantria dispar (L.). The effect of temperature on diapause development in gypsy moth eggs was examined by exposing individual eggs to temperature regimes of 5 degrees C interrupted by a single, brief exposure to an experimental temperature. Exposure to each of six experimental temperatures took place at six different times during diapause. The relative effect of the exposure on diapause development was estimated by comparing the duration of diapause in each of the treatments to the duration in a control treatment of constant 5 degrees C. The effect of each temperature did not remain constant throughout the diapause phase and the pattern of change was not uniform among the experimental temperatures. We propose a model of diapause where the developmental phase is controlled by two simultaneous temperature-dependent processes: a typical developmental response to temperature that is inhibited by a temperature-activated biochemical agent, and the temperature-dependent removal of the inhibiting agent. This simple model of two simultaneous and temperature-dependent processes explains 92% of the variability in diapause duration observed in the experimental regimes.     

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 induction and termination: north-south strain differences in Ostrinia nubilalis

Diapause induction and termination responses of a northern strain (Minnesota [MN]) of Ostrinia nubilalis were compared with those of a southern strain (Georgia [GA]). A thermoperiod in constant light (12 hr at 25 degrees C alternating with 12 hr at 4 degrees C) failed to induce diapause in GA larvae, but approximately 50% diapause induction was observed in the MN population. Moreover, the 50% of MN larvae that continued their development (i.e., underwent pupation and adult development) did so at a slower rate, as measured by days to pupation, than GA larvae. In the laboratory, diapausing MN larvae responded more slowly to the optimal light-dark (LD) cycle for terminating diapause, LD 16:8, than did GA larvae. In the field MN populations are univoltine (i.e., are characterized by one generation per year). A delayed termination response in the spring, coupled with a longer critical daylength for diapause induction as daylength decreases during late summer (earlier diapause) restricts the time during which development can occur as contrasted with GA populations. In addition, it is postulated that these two phenomena, coupled with a possibly slower growth rate in the MN insects as revealed under laboratory conditions, may collectively represent the basis for univoltinism in the field.     

豆天蛾越冬幼虫滞育解除后生物学特性的研究

[目的]豆天蛾Clanis bilineata tsingtauica以老熟幼虫进入滞育越冬,为探明豆天蛾滞育解除的机制.[方法]本研究设置4个不同温度梯度,在恒湿条件下,研究不同温度处理下豆天蛾滞育持续时间、化蛹及羽化的差异.[结果]温度对豆天蛾滞育解除存在一定影响.随着温度升高,豆天蛾滞育持续时间和蛹期逐渐缩短,在35℃条件下滞育持续时间和蛹期最短,分别为(34.4±0.3)d和(6.7±1.2)d;而化蛹率、蛹重随温度的升高呈先升高后降低,在25 ℃时,化蛹率最高为(80.60±0.26)％,在30 ℃时,蛹重最大为(4.21±0.07)g/头.豆天蛾成虫羽化率随温度升高而显著降低;25℃条件下,单雌产卵量最大,达到(204±9)粒.本室内条件下,豆天蛾滞育解除的有效积温为111¨日·度.[结论]在温度为25 ℃的条件下最有利于豆天蛾滞育解除后的生长发育.     

苹果蠹蛾滞育特性研究进展

苹果蠹蛾是苹果、梨等仁果类果树上的重要害虫,也是重要的入侵害虫。其具有寄主广泛、适生性强、蛀果为害等特点,一旦侵入很难彻底根除。老熟幼虫脱果后寻找隐蔽场所滞育的习性是其适应不利环境和维持种群繁衍的重要生存策略。本文就苹果蠹蛾幼虫滞育的诱导和终止因素、滞育场所的选取及聚集习性、滞育幼虫对环境的适应能力及内在生理生化特性以及针对滞育幼虫的防治技术等研究进行了综述,为探明苹果蠹蛾的灾变机理、预测预报和防治提供依据。     

Factors influencing the duration and termination of diapause in the Indian-meal moth, Plodia interpunctella

The influence of environmental factors on the duration of diapause in Plodia interpunctella larvae reared in short photoperiods at 20 or 25° C was examined, Diapause terminated most rapidly in long photoperiods at high temperatures. Pupation was more delayed, and mortality was higher, in darkness than in the presence of light. At 20° C, LD 16: 8 hastened diapause termination only slightly in unchilled samples. Chilling for 10 weeks at 10° C greatly reduced the duration of diapause at 20 or 25° C in constant darkness, and rendered LD 16:8 effective in terminating diapause at 20° C. In addition, the quite short duration of diapause under LD 16:8 at 25° C was further shortened by holding for 6–10 weeks at 10° C or below, or by holding in an outbuilding during winter. Holding diapausing larvae at 15 or 20° C proved less effective. Temperature rises from 20 to 25 or 30° C proved effective in terminating diapause. In one stock, the temperature at which diapause was induced influenced its subsequent duration. Lighting conditions during induction had less influence on duration than had temperature, and no difference occurred between pupation times of larvae reared at different population densities, Under all conditions tested, diapause lasted longer in a recently collected field stock than in a laboratory stock.     

Factors influencing the duration and termination of diapause in the Warehouse moth, Ephestia elutella

The influence of environmental factors on the duration of diapause was evaluated in larvae of Ephestia elutella (Hübner) reared in short photo-periods at 25C or below. Termination of diapause was hastened by long photoperiods, high temperatures, long periods at low temperature, or exposure to fumigants. Diapause terminated rapidly under long photoperiods at 30 or 25C, but not at 20C. The critical photoperiod for the termination of diapause was similar to that for induction, lying between 13 and 16 h at 25C. The longest duration of diapause occurred in constant darkness (DD) at 20C. However, batches of larvae reared at 20C in DD pupated a little sooner than batches reared under LD, if both were transferred at the start of diapause to warm, long-day conditions. Long exposure to low temperature reduced the number of long photoperiods necessary for the rapid termination of diapause at high temperature. Samples of larvae brought to the laboratory at monthly intervals from an unheated outbuilding in which they were overwintering, required an average of c. 200 days to pupate in DD at 25C when transferred in December, compared with only 32 days when transferred in February or March. By comparison, batches transferred to LD 16:8 at 25C required 39 days when transferred in December and 20–24 days in February and March. Holding at low temperature for long periods also encouraged synchronous emergence of the sexes. Duration of diapause was generally shorter in a laboratory stock than in a stock collected from the field.     

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.     

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.