Spring behavioral patterns of the apple blossom weevil

Individual pairs of overwintered adult apple blossom weevils, Anthonomus pomorum (L.), confined with apple twigs under different ambient temperatures in the laboratory and on apple trees in the field, were observed through day and night for their spring activities. Flight behavior in relation to ambient temperature was also investigated under laboratory conditions using flight stands. Both sexes displayed predominantly nocturnal behavior patterns in both the laboratory and the field. Feeding, crawling, and mating activities increased following sunset in the field or onset of scotophase in the laboratory while resting occurred most frequently during daylight hours. Results of the laboratory experiments showed that temperature affected significantly the activity patterns. The diel pattern of activities became less distinctive at higher temperatures (above 15°C), and total activities in crawling, feeding, and mating were suppressed significantly at lower temperatures (below 5°C). Over 97% of the test weevils initiated take-off response from flight stands at 20°C within the 30 min trial period; however, flight initiation rarely occurred at temperatures 12°C or below. Overall, results of the laboratory and field experiments indicate that A. pomorum is a remarkably cold-adapted insect with ability to crawl, feed, and mate at a few degrees above freezing, a physiological attribute necessary for the exploitation of early stages of apple bud development in the cold early spring.     

Uscana lariophaga, West-African egg parasitoid of the cowpea bruchid beetleCallosobruchus maculatus: photoperiod, parasitization and eclosion interactions

The diurnal pattern of parasitization and eclosion of the trichogrammatidUscana lariophaga Steffan, egg parasitoid of the cowpea bruchidCallosobruchus maculatus (Fabricius) was studied for L12:D12 photoperiods. The wasp parasitized eggs throughout each 24-h period with about 70% of the parasitization taking place during the first 12 h regardless whether it was the photophase or the scotophase. More female progeny was produced when the first 12-h period was photophase instead of scotophase. Eclosion of wasps took place over a period of 4 days and occurred during the second half of the scotophase and the first half of the photophase. The number of wasps eclosed during the photophase was similar to that eclosed during the scotophase. Average development time was 8.9 days at 30°C. Male development was completed 6 to 8 h before the females, hence a higher percentage of females emerged in the later eclosion peaks. During scotophases more females eclosed than during photophases. Although the results indicate that the wasp is able to perform under dark storage conditions the effect of permanent low light intensity remains to be studied.     

Early‐Season Headspace Volatiles from Apple and Their Effect on the Apple Blossom Weevil Anthonomus pomorum

Apple volatiles emitted at early phenological stages are little investigated, although they may influence behavior of early‐season pests. The apple blossom weevil Anthonomus pomorum is a herbivore pest of orchards in Europe. It colonizes apple trees in early season and oviposits into developing flower buds, often leading to economic damage. Using in situ radial diffusive sampling and thermal desorption, followed by GC/MS analysis, headspace volatiles from apple twigs with flower buds at three early phenological tree stages were identified and quantified. The volatile blend consisted of 13 compounds for the first, and increased to 15 compounds for the third phenological stage sampled. These blends included benzenoids, terpenes, and derivatives of fatty acids. A recombined synthetic blend served as the odor source in a still‐air dual‐choice olfactometer bioassay, in which individual male and female weevils were tested. Results from this behavioral test document an attraction of both sexes to odors of their host plant, suggesting that apple volatiles emitted in early season serve as olfactory cues for host location of A. pomorum in the field.     

Phenological analysis of spring colonisation of apple trees by Anthonomus pomorum

Adult apple blossom weevils, Anthonomus pomorum (L.) (Coleoptera: Curculionidae), leave their overwintering sites within and outside orchards to colonise apple trees in early spring. This study was conducted to characterize the temporal pattern of spring colonization of apple trees by overwintered weevils in relation to climatic conditions and apple bud stages, based on multiple mark-release-recapture experiments and field observations of foraging activities of weevils. The process of spring colonization of apple trees by overwintered weevils was related to thermal time totals above 0 °C. The dispersal into orchards initiated when the thermal time totals reached 161±27 (s.d.) degree-days (DD) calculated from January 1, or 117±16 DD from February 1. The daily dispersal speed of individual weevils within orchards was determined primarily by the maximum daily temperature, whereas crawling, feeding, and mating activities of weevils on apple trees were influenced by the mean evening temperature between 18:00 and 22:00 hours. On the other hand, the spring colonization of overwintered weevils was not synchronized with any specific apple bud stage, though the level of female foraging and reproductive activities on apple trees was related to apple bud stages. The overwintered weevils initiated dispersal into orchards over a wide range of bud developmental stages from little silver greenish tip B (51) to the mouse-ear stage C3 (54). These findings are discussed in relation to the ecology and pest management of this insect.     

Evidence for ‘dawn’ and ‘dusk’ hourglasses in Pimpla photoperiodic clock

Abstract

Resonance experiments (Nanda‐Hamner protocol) conducted at two temperatures for diapause termination in Pimpla instigator (Hymenoptera: Ichneumonidae) do not support the view that the photoperiodic clock has an oscillatory component, but suggest the presence of a non‐rhythmic timer or hourglass mechanism. These results are best explained by a two hourglasses model, one of which starts at light‐on and measures the photophase and the other is initiated by light‐off and measures the scotophase. The most likely hypothesis is that the ratio of photophase to scotophase lengths is the determining element. Good agreement is obtained between results predicted by two hourglasses model and results observed in Pimpla. The diurnal hourglass continues to run for long time (several months) in constant condition (LL) and does not require to be ‘turned over’ by D/L transition, in contrary to the classical model of hourglass which executes a single act of time measurement in extented phase and then stops. The most simple explanation is that some essential factor of diapause termination is synthesized during photophase and degraded during scotophase. Therefore an independent photoperiodic counter (for sommation of daily informations) is not necessary. The two hourglasses system serves as photoperiodic clock and accumulation of product as counter.     

Photoperiodic induction of pupal diapause in the flesh fly,Sarcophaga crassipalpis: embryonic sensitivity

Summary The last two days of embryonic development are crucial in programming pupal diapause in the flesh fly,Sarcophaga crassipalpis. Short daylength (greater than 10 1/2h of darkness) during this interval permits expression of diapause while long daylength during this brief sensitive stage eliminates the potential for diapause. Length of scotophase rather than photophase programs the diapause although three hours of light is needed to separate tandem dark periods. Early in the scotophase, photosensitivity is restricted to blue light (less than 540 nm). The scotophase can be divided into 4 phases according to the effect of light breaks on diapause expression. During Phase I (0–6 h after scotophase onset) embryos are highly sensitive to light interruption and diapause is effectively eliminated. A period of insensitivity to light, Phase II, extends from 6–hh after onset of scotophase. Light breaks at 10–11h coincide with the critical scotophase length and result in a partial reduction of diapause. In Phase IV, the scotophase reaction is complete and diapause competence is preserved even in the presence of light. Although light breaks result in elimination of diapause throughout Phase I, recovery time from a 1 h light break (length of darkness needed to counter the effect of a light break) differs dramatically depending upon when the light break is presented. Early in Phase I (0–3h) recovery from light interruption is rapid, while late in Phase I (4–6h), the effects of light are not readily reversible. The scotophase reaction thus appears to follow a step-wise progression rather than represent a simple linear response. We present a molecular model that could account for the dynamics of the scotophase reaction.     

高温对环带锦斑蛾幼虫滞育的抑制作用

本文报道了高温（31℃）对环带锦斑蛾幼虫滞育发生的抑制作用。当幼虫暴露于31℃ 时,所有个体都继续发育,与光周期无关。在诱导滞育的光周期条件(L12∶D12)下,光期的高温配合不同的暗期低温（15～28℃）,导致几乎所有个体滞育,但当暗期为5℃时,滞育率反而下降;相反,当光期的低温配合不同持续时间的暗期高温（31℃）时,则几乎所有的个体都继续发育,这说明高温在暗期发挥着重要的作用。在暗期给予不同时间长度（2、4、 6、8、10、12 h）的高温处理,结果表明一个2 h的高温处理就能有效地抑制滞育的发生。在暗期的不同时间给予4 h高温处理,显示了幼虫在暗期开始后的第一个4 h (18:00～22:00 )对高温最敏感,完全抑制了滞育的发生。最后讨论了高温调节滞育机制在该虫生活史上的适应意义。     

Pheromone-binding protein and general odorant-binding protein of Sesamia nonagrioides: sex- and diel-dependent expression

The expression of a pheromone‐binding protein (PBP) and a general odorant‐binding protein (GOBP) in Sesamia nonagrioides (Lef.) (Lepidoptera: Noctuidae) was studied. Lymantria dispar's PBP1 antibody yielded an immunoreactive band with an apparent MW of approximately 14.8 kDa, present specifically in the antennae of both sexes, with males having approximately three‐fold the quantity found in females. Furthermore, Manduca sexta's odorant‐binding protein‐2 (GOBP2) antibody recognized a band at approximately 14.5 kDa in the antennae of both sexes. Levels of both proteins were compared between scotophase and photophase periods in insects that were raised under L16:D8 or under constant light. The level of GOPB2 was significantly lower in both sexes during photophase and continuous light; whereas the level of the PBP was significantly lower in females’ antennae, in males’ antennae it remained at the same level as that found during the scotophase.     

Diel periodicity and influence of age and mating on female sex pheromone titre in Estigmene acrea (Lep., Arctiidae)

Abstract:  Calling behaviour, diel periodicity, and effect of age and mating on female sex pheromone titre in Estigmene acrea (Drury) were studied under laboratory conditions. Forty-five per cent of females started calling during the first scotophase, but the highest number of calling females was observed during the second, third and fourth scotophases. Calling behaviour occurred from the third hour after dark until just before the end of the scotophase. However, females exhibited a bimodal pattern of calling with the first peak occurring between 4 and 6 h and a second peak at 10 h after the onset of scotophase. The mean onset of calling time differed significantly with age. Older females showed a tendency to call longer, but there was no significant difference. The amount of (Z,Z)-3,6-cis-9, 10-epoxyheneicosadiene in females was quantified from the first scotophase following emergence, until the fifth scotophase. Glands of 0-day-old females presented a higher content of pheromone compared with that found in glands of 1-, 2-, 3- and 4-day-old females. Pheromone titre was determined at 2-h intervals throughout the third scotophase and photophase. (Z,Z)-3,6-cis-9,10-epoxyheneicosadiene was found in the gland during the scotophase as well as the photophase. However, there was no consistent pattern of pheromone production throughout the scotophase or photophase. Mated females of E. acrea produced significantly less pheromone than virgin females.     

Locomotor activity in adult Pyrrhocoris apterus (Heteroptera) in relation to sex, physiological status and wing dimorphism

The pattern of locomotor (walking) activity was studied in adult males and females of short‐winged (brachypterous) and long‐winged (macropterous) morph of the flightless bug Pyrrhocoris apterus (Linnaeus) (Heteroptera: Pyrrhocoridae) under constant laboratory conditions. Walking activity was measured with a computerized video system and analysed with respect to sex, physiological status (reproduction, diapause and reproductive arrest of non‐diapause type) and wing dimorphism of the bugs. The largest duration was observed in the macropterous females with reproductive arrest of non‐diapause type (average 6 h per day) and the shortest duration in diapausing brachypterous females and males (average less than 2 h per day). This was reflected also in the overall time spent by walking during the first 14 days after imaginal ecdysis. The time spent by walking significantly increased in the macropterous morph as the bugs aged, whereas in diapausing brachypters the time spent by walking decreased with age. No linear relationship between walking activity and age was found in reproductive brachypterous morph. The bugs of all experimental groups moved mostly during the photophase and were almost inactive during the scotophase. Thus, walking activity in P. apterus is diurnal, irrespective of the wing morph, physiological status, sex and age. Contrary to the macropterous morph, where the locomotor activity of females during photophase was significantly higher than in males, no significant differences were found between the locomotor activities of brachypterous males and females. The observed differences in locomotor activity are discussed in relation to different roles of two wing morphs in the life history of this heteropteran.     

Flight activity of three Spodoptera spp., Spodoptera litura, S. exigua and S. depravata, measured by flight actograph

Flight activities of three Spodoptera species were measured by the aid of flight actograph: S. litura and S. exuiga being regarded as long‐distance migratory insects, and S. depravata being non‐migratory and diapause‐inducible species. In all species tested, flight activities were observed only in scotophase, males showed far higher activities than females, being several times higher at the time of maximum flight activity, which was observed within 2 days after adult eclosion. Total flight activity in males was highest in S. litura, some being flyable even 12 days after eclosion, followed by S. exigua being one‐third compared to the former species, while in S. depravata flight activity was nearly half of that of the second species and most ceased to fly within a week after eclosion. There occurred species‐specific daily rhythms in flight activity during respective scotophase. In S. litura, both females and males exhibited a peak of flight activity shortly after light‐off and exhibited the second flight activity in late scotophase, the females slightly but the males more actively compared to early scotophase. In S. exigua, both sexes did not respond to light‐off, did not show a peak of flight activity in early scotophase, whereas males, but not females prominently increased activity toward the end of scotophase. In S. depravata, both sexes exhibited a peak of flight activity in early scotophase, and the males revived flight activity, being maximum shortly before light‐on, but the females did not show a clear rhythm in flight activity. These features observed in flight activity were discussed in relation with migratory capability.     

Effect of temperature and photoperiod on the induction of diapause in the mite Metaseiulus occidentalis

Diapause in a predaceous mite, Metaseiulus occidentalis, from a Californian vineyard population is a photoperiodically induced, facultative, adult reproductive diapause in females. The laboratory-determined critical photophase at 19°C was estimated at 11·2 hr. At 16°C, the critical photophase under laboratory conditions was approximately 11·6 hr. Temperature influenced the photoresponse of M. occidentalis so that diapause was entirely averted at temperatures of 22, 25, and 30°C. Aestival diapause at higher temperatures and long photophases was lacking. Development was continuous under constant darkness at all the temperatures tested. Diapause termination in laboratory-reared mites occurred spontaneously under the inductive conditions. Under constant 19°C temperatures, females responded to photophases so that diapause was terminated most rapidly under a 16 hr photophase (in 18·6 days); the 12 and 8 hr photophases, at this temperature, were next in their effectiveness, with 27·9 and 73·0 days, respectively, required for termination.     

Diapause affects cuticular hydrocarbon composition and mating behavior of both sexes in Drosophila montana

Envipnmental cues,mainly photoperiod and temperature,are known to control female adult reproductive diapause in several insect species.Diapause enhances female survival during adverse conditions and postpones progeny production to the favorable season.Male diapause(a reversible inability to inseminate receptive females)has been studied much less than female diapause.However,if the males maximized their chances to fertilize females while minimizing their energy expenditure,they would be expected to be in diapause at the same time as females.We investigated Drosophila montana male mating bchavior under short-day conditions that induce diapause in females and found the males to be reproductively inactive.We also found that males reared under long-day conditions(reproducing individuals)court reproducing postdiapause fermales,but not diapausing ones.The diapausing fies of both sexes had more long-chain and less short-chain hydrocarbons on their cuticle than the reproducing ones,which presumably increase their survival under stressful conditions,but at the same time decrease their attractiveness.Our study shows that the mating behavior of females and males is well coordinated during and afier overwintering and it also gives support to the dual role of insect cuticular hydrocarbons in adaptation and mate choice.     

The role of the main photophase on dark-time measurement used for diapause determination in the Indian meal moth, Plodia interpunctella

Abstract.  The Indian meal moth Plodia interpunctella Hubner (Lepidoptera: Pyralidae) measures night length and enters diapause as a last-instar larva. To examine the role of photophase on dark-time measurement, the main LD 7 : 17 h photoperiod is disrupted by various lengths of darkness at 25 °C. When the light phase is not disrupted, the incidence of diapause is 76%. As the dark pulse disrupting a 7-h photophase becomes longer, the incidence of diapause decreases. To detect the dynamic kinetics of the time-measuring process, the main scotophase of 17 h is scanned by a 2-h light pulse. When the dark pulse in a 7-h photophase is fixed at 1 h after dawn and its duration is varied systematically from 1 to 3 h, or when the end of the dark pulse is fixed at 1 h before dusk, diapause is prevented completely by a 2-h light pulse inserted in the middle of 17-h darkness. These results are compared with those of a single night interruption of a 17-h scotophase with a 2-h light pulse but with an intact 7-h photophase. The disruption of a 7-h photophase by a dark pulse shifts the descending and ascending slopes of the response curve to some extent toward dawn and dusk, respectively, indicating that the dark pulse tends to shorten the critical length of dark time for diapause induction. When the main photophase (7 h) is interrupted by a 1-h dark pulse at 3–4 h after dawn, the 2-h scanning light pulse in the main scotophase (17 h) appears to act effectively as a dusk signal in the early scotophase. However, those in the mid- and late scotophase do not define the critical night length from dusk as sharply as for the critical night length from a 2-h light pulse to dawn. The results indicate the importance of photophase in the dark-time measurement.     

Age-dependent cyclic locomotor activity in the cricket, Gryllus bimaculatus, and the effect of adipokinetic hormone on locomotion and excitability

Excitability and locomotor activity of male and female last instar larvae and adults of the two-spotted cricket are measured under crowded conditions, allowing the animals to interact with conspecifics during observations. Male and female last instar larvae display age-dependent cyclic patterns of activity with maxima during early to mid scotophase and minima during early photophase. A period of low locomotor activity without time of day-dependent cyclic changes starts 1 day before the final moult and lasts until 1 day after the moult. Then, both excitability and locomotor activity increase and become cyclic again within 2 or 3 days. The cyclic changes gradually dampen in adult females older than 6 days and finally cease. When injected into photophase larvae and adults, adipokinetic hormone (AKH) increases excitability and locomotor activity in a dose-dependent manner, whereas it has no such effect when injected into scotophase animals. Other behaviours (jumping, hind wing trembling) that mostly occur in scotophase crickets are also increased by injecting AKH into photophase crickets. We argue that AKH could be responsible for linking the endogenous clock output with the cyclic changes in locomotor activity. Furthermore, AKH may serve to synchronise metabolism and behaviour to optimise larval development and reproduction.     

Sex pheromone titre in the glands of Spodoptera litura females: circadian rhythm and the effects of age and mating

The present study investigates the effects of age and mating status on the circadian variations of gland sex pheromone titre in female Spodoptera litura Fabricius. Similar to other nocturnal moths, S. litura females exhibit circadian variations of gland sex pheromone contents, with higher levels during scotophase and lower levels during photophase. The sex pheromone titre in the glands peaks during the first scotophase after eclosion and sharply declines afterwards. Higher pheromone contents during scotophase may facilitate female reproductive activities, and the negative relationship between pheromone titre and female calling is likely the result of pheromone release during female calling. Interestingly, the present study demonstrates that mated S. litura females have significantly higher sex pheromone titre in their pheromone glands (PGs) than virgin females. This finding contrasts with all previous studies of other insect species, in which mating generally reduces the sex pheromone titre in female PGs. In S. litura, mating and male accessory gland fluids can suppress female calling behaviours and re‐matings. These results suggest that the suppression of female calling behaviours by mating and male accessory gland fluids may significantly reduce the release of sex pheromones and thus result in higher sex pheromone titre in the PGs of mated females.     

Environmental regulation of female calling and male pheromone response periodicities in the codling moth (Laspeyresia pomonella)

Codling moth female calling and male pheromone responsiveness under the defined conditions of 23°C and light:dark (LD) 16:8 occurred primarily during scotophase. Under either continuous photophase or scotophase females called with periodicities very similar to their periodicity under the LD cycle, indicating that the rhythmicity is circadian. Male response rhythmicity was maintained under continuous photophase. A decrease in the temperature from 23° to 16°C resulted in a reduction in the proportion calling when the decrease in temperature occurred during scotophase and a shift of maximal calling into photophase when the decrease in temperature occurred 3 hr prior to the initiation of scotophase. Decreases of temperature from 23° to 16°C and of light intensity did not produce similar shifts in the periodicity of male upwind orientation. Of 6 pheromone dosages from 10^?5 to 10² μg, 10^?1 and 10⁰ μg elicited the most male upwind orientation.     

Hormonal regulation of sex pheromone biosynthesis in the turnip moth,Agrotis segetum

Pheromone production in the female turnip moth, Agrotis segetum, is under the control of a brain factor. This factor was demonstrated to be a proteinaceous substance termed pheromone biosynthesis activating neuropeptide-like substance (PBAN-like substance). The sex pheromone of Swedish A. segetum includes (Z)-5-decenyl acetate, (Z)-7-dodecenyl acetate, and (Z)-9-tetradecenyl acetate as major components. Decapitation of a female decreased pheromone production significantly. Pheromone production was restored by injection of homogenates of either male or female brain-suboesophageal ganglion or the corpora cardiaca alone. Pheromonotropic activity was also found in homogenates of the female thoracic ganglion and abdominal ganglion that were obtained during scotophase. Injection of female brain and thoracic ganglion homogenates made from insects during the scotophase induced two and four times as much Z7-12:OAc, respectively, as injection with similar homogenates from photophase. As little as one-eighth female equivalent (FE) brain homogenate was sufficient to increase the amount of Z7-12:OAc. The effect of brain homogenate on pheromone titer reached its maximum after 30 min. The activity of the PBAN-like substance present in female brain extracts was not correlated to the age of the donor. Injection of hemolymph collected during either photophase or scotophase into decapitated females did not increase the pheromone titer. The target site of the PBAN-like substance was not the pheromone gland, and the ventral nerve cord was not involved in the transportation of the PBAN-like substance, which implies a mode of action different from what has been reported in other moths. Brain homogenates obtained during photophase from females of African A. segetum, Spodoptera littoralis, or Ostrinia nubilalis as well as synthetic Bombyx-PBAN also induced pheromone production in decapitated Swedish female A. segetum. © 1995 Wiley-Liss, Inc.     

The effect of temperature and light conditions on diapause induction in a Korean population of Neoseiulus womersleyi Schicha (Acari: Phytoseiidae)

To determine the condition for diapause induction of a Korean population of Neoseiulus womersleyi, combinations of constant temperatures (14, 16, 18, 20 and 25 °C) and photoperiods (0, 8, 10, 12, 14, 16 and 24 h photophase) were used from egg to adult emergence. Diapause induction was determined by reproductive cessation of adult females. Lower temperature and shorter photophase resulted in higher diapause induction. Critical photophases for diapause induction were 10 and 12 h at 18 and 16 °C, respectively. Diapause-induced N. womersleyi adult females consumed significantly fewer eggs of the two-spotted spider mite, Tetranychus urticae, than non-induced females. Field monitoring of N. womersleyi showed that there was no egg-bearing female after 282 Julian date, while a model estimated complete diapause induction at 288 Julian date. Diapause of this predatory mite occurred approximately 2 weeks before diapause of its main prey, T. urticae, in Korean apple orchards. Further study perspectives are discussed relative to the spider mite biological control system in fruit orchards.     

Diurnal locomotion and feeding activities of two rice-ear bugs,Trigonotylus caelestialium and Stenotus rubrovittatus (Hemiptera: Heteroptera: Miridae)

Diurnal locomotion and feeding activities of Trigonotylus caelestialium (Kirkaldy) and Stenotus rubrovittatus (Matsumura) were investigated using a video camera and electrical penetration graph. Diurnal locomotion activity of T. caelestialium was higher in photophase than in scotophase, whereas that of S. rubrovittatus was higher in scotophase than in photophase. No difference was observed in the locomotion activity of T. caelestialium between mated and unmated bugs or between males and females. Locomotion activity of S. rubrovittatus was different between the sexes. The activity of females was higher than that of males. Diurnal rhythms of feeding activity were obscure compared with those of the locomotion activities in both mirids. The feeding behavior of T. caelestialium was significantly more active in the photophase than in the scotophase. In S. rubrovittatus, feeding activity of males was higher in the scotophase than in the photophase, whereas females showed no such difference. It is thought that both species of mirid bugs are active during the daytime and nighttime, although the locomotion and feeding activities of T. caelestialium were high in the photophase, while those of S. rubrovittatus were high in the scotophase.