94 research outputs found

    Shifting body weight-fecundity relationship in a capital breeder : maternal effects on egg numbers of the autumnal moth under field conditions

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    In the literature, various environmental factors are described as being capable of influencing the reproductive output of insect females irrespective of their body size. Still, female body size or weight is widely used as a proxy for fecundity. In the present study, a seven-year data set on the autumnal moth, Epirrita autumnata (Borkhausen) (Lepidoptera: Geometridae), was used to analyze whether the body weight-fecundity relationship in this capital breeding, cyclic forest defoliating lepidopteran is constant across years. Ambient temperature conditions and density of conspecifics during larval development, the length of the pupal period, as well as moth densities in the parent generation were examined as factors capable of modifying the body weight-fecundity relationship. While the regression slope of potential fecundity (total egg numbers per female) on pupal mass was constant across years, the mean total egg number per given body weight (the regression intercept) was significantly different between years. This residual variance in egg numbers after controlling for the effect of pupal mass was best explained by the pooled geometrid density (autumnal and winter moths) in the parent generation. The total egg number per given body weight decreased with increasing density of geometrid moths in the parent generation. Thus, maternal density effects on offspring fecundity were found in this system. Their rather weak nature suggests, however, that this maternal effect alone does not have the potential of causing cyclic population dynamics in the autumnal moth

    Larval parasitism of the autumnal moth reduces feeding intensity on the mountain birch

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    Plants respond to grazing by herbivorous insects by emitting a range of volatile organic compounds, which attract parasitoids to their insect hosts. However, a positive outcome for the host plant is a necessary precondition for making the attraction beneficial or even adaptive. Parasitoids benefit plants by killing herbivorous insects, thus reducing future herbivore pressure, but also by curtailing the feeding intensity of the still living, parasitised host. In this study, the effect of parasitism on food consumption of the 5th instar larvae of the autumnal moth (Epirrita autumnata) was examined under laboratory conditions. Daily food consumption, as well as the duration of the 5th instar, was measured for both parasitised and non-parasitised larvae. The results showed that parasitism by the solitary endoparasitoid Zele deceptor not only reduced leaf consumption significantly but also hastened the onset of pupation in autumnal moth larvae. On the basis of the results, an empirical model was derived to assess the affects on the scale of the whole tree. The model suggests that parasitoids might protect the tree from total defoliation at least at intermediate larval densities. Consequently, a potential for plant–parasitoid chemical signalling appears to exist, which seems to benefit the mountain birch (Betula pubescens ssp. czerepanovii) by reducing the overall intensity of herbivore defoliation due to parasitism by this hymenopteran parasitoid

    Expansion of the winter moth outbreak range : no restrictive effects of competition with the resident autumnal moth

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    1. Both direct and indirect competition can have profound effects on species abundance and expansion rates, especially for a species trying to strengthen a foothold in new areas, such as the winter moth (Operophtera brumata) currently in northernmost Finland. There, winter moths have overlapping outbreak ranges with autumnal moths (Epirrita autumnata), who also share the same host, the mountain birch (Betula pubescens ssp. czerepanovii). Competitive interactions are also possible, but so far unstudied, are explanations for the observed 1–3 years phase lag between the population cycles of the two moth species. 2. In two field experiments, we studied host plant-mediated indirect inter-specific competition and direct interference/exploitation competition between autumnal and winter moths. The experimental larvae were grown either with the competing species or with the same number of conspecifics until pupation. Inter-specific competition was judged from differences in pupal mass (reflecting lifespan fecundity), larval development time and larval survival. 3. Larval performance measurements suggested that neither direct nor indirect interspecific competition with the autumnal moth reduce the growth rate of winter moth populations. Winter moths even had a higher probability of survival when reared together with autumnal moths. 4. Thus, we conclude that neither direct nor indirect inter-specific competition is capable of suppressing the spread of the winter moth outbreak range and that both are also an unlikely cause for the phase lag between the phase-locked population cycles of the two moth species

    Local outbreaks of Operophtera brumata and Operophtera fagata cannot be explained by low vulnerability to pupal predation

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    One of the unresolved questions in studies on population dynamics of forest Lepidoptera is why some populations at times reach outbreak densities, whereas others never do. Resolving this question is especially challenging if populations of the same species in different areas or of closely-related species in the same area are considered. The present study focused on three closely-related geometrid moth species, autumnal Epirrita autumnata, winter Operophtera brumata and northern winter moths Operophtera fagata, in southern Finland. There, winter and northern winter moth populations can reach outbreak densities, whereas autumnal moth densities stay relatively low. We tested the hypothesis that a lower vulnerability to pupal predation may explain the observed differences in population dynamics. The results obtained do not support this hypothesis because pupal predation probabilities were not significantly different between the two genera within or without the Operophtera outbreak area or in years with or without a current Operophtera outbreak. Overall, pupal predation was even higher in winter and northern winter moths than in autumnal moths. Differences in larval predation and parasitism, as well as in the reproductive capacities of the species, might be other candidates

    Responses of generalist invertebrate predators to pupal densities of autumnal and winter moths under field conditions

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    1. Generalist natural enemies are usually not considered as being capable of causing population cycles in forest insects, but they may influence the population dynamics of their prey in the low density cycle phase when specialist enemies are largely absent. 2. In the present field study, the total response of the generalist invertebrate predator community to experimentally established pupal densities of the closely related autumnal (Epirrita autumnata) and winter moths (Operophtera brumata) was analysed. 3. Due to the high amount of variation in the dataset, the exact shape of the response curve could not be convincingly estimated. Nevertheless, two important conclusions can be drawn from the analyses. 4. Firstly, the natural invertebrate predator community seems to become saturated at rather low densities of both autumnal and winter moth pupae. Secondly, the predator community seems to become saturated at much lower densities of autumnal than of winter moth pupae. 5. Furthermore, pupal mass was significantly negatively correlated with invertebrate predation probability in autumnal moth pupae. 6. These results indicate that differences in the predator assemblage being able to consume pupae of the two moth species, as well as different handling times, could be responsible for the substantially higher predation rates in winter than in autumnal moth pupae. 7. As a consequence, the population dynamics of autumnal moths might be less affected by generalist invertebrate predators than those of winter moths, as autumnal moths seem able to escape from the regulating influence of generalist predators at much lower population densities than winter moths

    Reversed impacts by specialist parasitoids and generalist predators may explain a phase lag in moth cycles : a novel hypothesis and preliminary field tests

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    Among cyclic populations of herbivores, inter-specific temporal synchrony has been attributed to both climatic factors and trophic interactions. In northern Europe, winter and autumnal moths undergo regular 9–11 year population cycles. The winter moth cycle has typically been phase-locked with that of the autumnal moth, but with a 1–3- year phase lag. We examined potential effects of natural enemies on this phase lag using field experiments and observational data. We found that larval parasitism was significantly higher in autumnal than in winter moths. Conversely, pupal predation by generalist invertebrates was clearly greater in winter than in autumnal moths. The difference in parasitism rates may contribute to the earlier collapse of the autumnal moth cycle. In addition, the phase lag may be strengthened by higher pupal mortality in winter moths in the early increase phase of the cycles. As a consequence, we put forward a hypothesis on reversed effects of natural enemies, providing a potential explanation for phase-lagged population cycles of these moth species

    Identification of insects, spiders and mites in vegetable crops. Workshop Manual, 2nd edition

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    Accurate and confident identification of the insects, spiders and mites in vegetable crops is the first step towards successful management of pests and natural enemies. It is an essential prerequisite for crop monitoring, which is the backbone of an effective pest management program. This workshop manual and trainer's handbook were compiled as part of an insect, spider and mite identification program for Australian vegetable growers. The workshop training is designed to help growers to: • know how to collect and preserve insects for identification • be able to classify most common insects (particularly those of horticultural significance) into broad groups • appreciate the importance of these groups in pest, predator and parasite identification and management • collect and classify some insect pests, predators and parasites of horticultural importance

    Japanese understanding of salvation : soteriology in the context of Japanese animism

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    Text in GermanCosmology and sociology show that animism is the predominant worldview of Japan. Concepts of God, the issue of controlling mana-power, implications of the Japanese soul-concept, the orientation of the conscience and ancestor veneration are critically discussed with Christian beliefs. When compared to the Biblical peace-concept the Japanese peace-concept shows an aesthetic bias that has to be overcome by adding the concept of justice. Japanese soteriology has no reference to God the Creator, whose proclamation is the basis of understanding man's misfortune as rebellion against God and his salvation as reconciliation with Him. Cosmologically speaking, man experiences his misfortune as fear of super-human powers. Salvation is sought through defensive magic and fortunetelling. Christianity acknowledges security as a basic human need but seeks protection and guidance from God. The main focus of Japanese soteriology is in the field of sociology, which in Japan also includes the relationship with the living dead. Misfortune is mainly experienced as shame and ostracism, salvation as rehabilitation. Defilement of naturally good humans is a central theme in Japan's understanding of man's misfortune. The Christian concept of sin, on the contrary, has a theological and an ontological dimension as well. In Japan salvation is understood solely as this-worldly benefits such as health, happiness, prosperity, fertility, and longevity. But in Christianity suffering is a central theme. An overly strong orientation on "this world" can lead to ethical shallowness, overemphasizing the "coming world" to a dangerous ethical relativism. Christian soteriology must keep the tension between these two extremes. The hope of the coming world must neither be robbed of its historical truth by its transformation into a principle, nor must it be historically ineffective.As for his relationship with God, man is solely the object of God's salvation. But as for Christian acts, man is called to act "in the Lord".Ausführungen zur Kosmologie und Soziologie zeigen, daß das vorherrschende Weltbild Japans das des Animismus ist. In kritischer Auseinandersetzung mit dem Christentum werden der Gottesbegriff, der Gebrauch der Mana-Kraft, Implikationen des Seelenbegriffs, die Gewissensorientierung und die Ahnenverehrung diskutiert. Die Gegenüberstellung mit dem biblischen Friedensbegriff zeigt, daß der japanische Friedensbegriff seine ästhetische Einseitigkeit durch die Erweiterung um den Aspekt der Gerechtigkeit überwinden muß. In Japan hat die Soteriologie keinen Bezug zu Gott, dem Schöpfer, dessen Verkündigung die Grundlage für das Verständnis des Unheils als Rebellion gegen ihn, des Heils als Versöhnung mit ihm ist. Kosmologisch wird das Unheil in Japan als Angst vor übermenschlichen Mächten erfahren, das Heil durch Schutzzauber und Wahrsagerei gesucht. Das Christentum erkennt das Grundbedürfnis der Sicherheit an, sucht Schutz und Führung aber bei Gott. Das Schwergewicht japanischer Soteriologie liegt im Bereich der Soziologie, zu der in Japan auch die Beziehung zu den living dead gehört. Unheil wird vor allem als Beschämung und Ächtung, Heil als Rehabilitation erfahren. Im japanischen Unheilsverständnis nimmt Verunreinigung des an sich guten Menschen einen hohen Stellenwert ein. Das christliche Sündenverständnis hat dagegen auch eine theologische und ontologische Dimension. Heil wird in Japan rein diesseitig als Gesundheit, Glück, Reichtum, Fruchtbarkeit und langes Leben verstanden. Dagegen spielt in der christlichen Heilslehre das Leiden eine zentrale Rolle. Eine zu starke Orientierung auf "diese Welt" kann zu ethischer Seichte, eine zu starke Orientierung auf die "kommende Welt" zu einer gefährlichen ethischen Relativierung führen. Die christliche Soteriologie muß die Spannung zwischen beiden Polen aufrechterhalten. Die Hoffnung auf die kommende Welt darf weder durch ihre Erhebung zum Prinzip ihrer geschichtlichen Wahrheit beraubt werden, noch darf sie selbst geschichtlicher Wirklichkeit entbehren. Was die Beziehung des Menschen zu Gott angeht, ist der Mensch ganz und gar Objekt des göttlichen Heilshandelns. Was aber das christliche Handeln angeht, ist der Mensch zum Handeln "im Herrn" berufen.Christian Spirituality, Church History and MissiologyD.Th. (Missiology

    Area-efficient snoopy-aware NoC design for high-performance chip multiprocessor systems

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    Manycore CMP systems are expected to grow to tens or even hundreds of cores. In this paper we show that the effective co-design of both, the network-on-chip and the coherence protocol, improves performance and power meanwhile total area resources remain bounded. We propose a snoopy-aware network-on-chip topology made of two mesh-of-tree topologies. Reducing the complexity of the coherence protocol - and hence its resources - and moving this complexity to the network, leads to a global decrease in power consumption meanwhile area is barely affected. Benefits of our proposal are due to the high-throughput and low delay of the network, but also due to the simplicity of the coherence protocol. The proposed network and protocol minimizes communication amongst cores when compared to traditional solutions based either on 2D-mesh topologies or in directory-based protocols. (C) 2015 Elsevier Ltd. All rights reserved.Roca Pérez, A.; Hernández Luz, C.; Lodde, M.; Flich Cardo, J. (2015). Area-efficient snoopy-aware NoC design for high-performance chip multiprocessor systems. Computers and Electrical Engineering. 45:374-385. doi:10.1016/j.compeleceng.2015.04.020S3743854

    The role of spiders as predators of two lepidopteran Brassica pests

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    Spiders are thought to play a significant role in limiting pest outbreaks in agroecosystems such as vineyards, orchards and cotton. The diversity and impact of spiders in vegetable crops are less well understood, although there is evidence that predators may be important for suppression of lepidopteran pests in Brassica crops, particularly early in the season before parasitoids become established. Sampling was conducted in early season plantings of Brassicas in the Lockyer Valley (South East Queensland, Australia) in order to determine the most commonly occurring spider families. The most numerous were Theridiidae, which were more strongly associated with cauliflower and poorly associated with cabbage. The Lycosidae and Clubionidae/Miturgidae (formerly in the ‘catch-all’ family Clubionidae) also occurred commonly. Lycosidae (and to a lesser extent Salticidae) had above average abundance in Chinese cabbage and below average abundance in broccoli compared with average abundance for these spider families; Clubionidae/Miturgidae had above average abundance in cauliflower. Laboratory studies were then conducted to explore the predatory capacity of these three most commonly occurring spider families. All three were capable of feeding on larvae of the diamondback moth, Plutella xylostella (Linnaeus), and cabbage cluster caterpillar, Crocidolomia pavonana (Fabricius), under laboratory conditions. Theridiidae, which are thought to prey on small pests such as leafhoppers and aphids, were able to successfully attack larvae up to five times their body size. Predation rates varied from an average of 1.7 (SE = 0.47) (1.6 control corrected) larvae consumed over a 24 h period in the case of the Theridiidae, to 3.3 (SE = 0.60) larvae for the Clubionidae/Miturgidae
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