茶园黑刺粉虱越冬虫态及空间分布型研究

黑刺粉虱Aleurocanthus spiuiferus是茶园重要害虫之一,为明确黑刺粉虱在北方茶园的越冬分布型及越冬虫态,通过对茶园黑刺粉虱越冬代虫源进行调查,分冠层统计不同越冬时期各虫态的发生量,利用聚集度指标分析、m*-m回归方程分析和Taylor幂法则回归方程分析其空间分布型。结果显示黑刺粉虱越冬代田间分布型为聚集分布,种群聚集均数λ>2,聚集原因为种群自身产卵习性与环境因素共同作用结果;各虫态在茶树冠层间的分布存在差异,卵和1龄若虫主要分布于树冠中、上部,3龄、4龄若虫和伪蛹主要分布于树冠中、下部;随着越冬时间推移,卵和低龄若虫占比逐渐减少,至越冬结束黑刺粉虱4龄若虫和伪蛹占种群总量的80%。本研究明确了黑刺粉虱在北方茶园以各龄若虫和伪蛹越冬,越冬期间可缓慢发育至4龄若虫和伪蛹,越冬代田间分布型为聚集分布,研究结果可为黑刺粉虱精准预测预报和合理制定综合防治措施提供技术支持。     

How do host plant use and seasonal life cycle relate to insect body size: A case study on European geometrid moths (Lepidoptera: Geometridae)

We used European geometrid moths (>630 species) as a model group to investigate how life history traits linked to larval host plant use (i.e., diet breadth and host-plant growth form) and seasonal life cycle (i.e., voltinism, overwintering stage and caterpillar phenology) are related to adult body size in holometabolous insect herbivores. To do so, we applied phylogenetic comparative methods to account for shared evolutionary history among herbivore species. We further categorized larval diet breadth based on the phylogenetic structure of utilized host plant genera. Our results indicate that species associated with woody plants are, on average, larger than herb feeders and increase in size with increasing diet breadth. Obligatorily univoltine species are larger than multivoltine species, and attain larger sizes when their larvae occur exclusively in the early season. Furthermore, the adult body size is significantly smaller in species that overwinter in the pupal stage compared to those that overwinter as eggs or caterpillars. In summary, our results indicate that the ecological niche of holometabolous insect herbivores is strongly interrelated with body size at maturity.     

Fecundity and size in the housefly: investigations of some environmental sources and genetic correlates of variation

Environmental sources and genetic correlates of variation in fecundity and size were studied in field and laboratory housefly populations in central Iowa, U.S.A. Electrophoresis of enzymatic proteins was used to monitor genotypes and heterozygosity. In the field, mean fecundity declined as adult densities increased. Fecundity varied greatly within breeding seasons. Fly body size varied spatially and temporally during summer and winter. Fecundity and size were positively correlated. Size was independent of genotypes at the six loci studied. No relationship was observed between heterozygosity and the magnitude or variability of body size.     

Gyne development in the Argentine ant Iridomyrmex humilis: role of overwintering and queen control

Abstract A possible stimulatory effect of overwintering on gyne development in Iridomyrmex humilis (Mayr) was investigated. Although gyne-potent larvae are present in the nest throughout the year, small queenless colony fragments composed of freshly overwintered ants (collected in late winter or early spring) produced 3–8 times more gynes than comparable fragments made up of non-freshly overwintered ants (collected at other times of the year). Apparently, this stimulatory effect of overwintering acts on both the developmental potential of larvae and the tendency of workers to rear sexually competent larvae as gynes; queenless colony fragments in which either the brood or workers were freshly overwintered produced more gynes than fragments composed of non-freshly overwintered workers or brood but fewer than fragments containing both brood and workers freshly overwintered. This increased sexualization potential of larvae due to overwintering is enough to overcome weak pheromonal inhibition of queens associated with low queen number; a single queen in a large freshly overwintered colony fragment is insufficient to inhibit gyne development, whereas ten queens are totally inhibitory. In non-freshly overwintered colony fragments one queen is completely inhibitory. Variability in egg developmental potential according to queen age does not appear to play a major role in the seasonal production of gynes, because at least some eggs of very young queens (less than 3 weeks old) are capable of gyne development. In the field this stimulatory effect of overwintering is superimposed on a seasonal fluctuation in the combined strength of pheromonal queen control. In southern France, gynes are produced only in spring where they arise primarily from overwintered larvae just after a sharp drop in queen number, and presumably the total level of inhibitory queen pheromone, due to the massive execution of queens by workers.     

Effect of mating on survival at low temperature in females of the Japanese common grass yellow,Eurema mandarina

1. In some insects that overwinter as adults, mating occurs both before and after overwintering. Two hypotheses have been proposed to explain the adaptive significance of pre‐overwintering copulation of females. One is the bet‐hedging hypothesis, which explains pre‐overwintering copulation as a preparation for less chance of mating in the following spring. The other is the nuptial gift hypothesis, which states that secretions derived from males increase overwintering success of females. 2. In Eurema mandarina, both diapause autumn‐ and non‐diapause summer‐form male adults emerge with autumn‐form female adults in the last generation in a year. Most autumn‐form females mate with summer‐form males before winter, and re‐mate with autumn‐form males in the following spring. Because autumn‐form females have sufficient chances for mating after overwintering, the nuptial gift hypothesis has been regarded as the more probable hypothesis. 3. To test the nuptial gift hypothesis, the survival period was compared under short‐day conditions at 10 °C between mated and unmated females that had been reared on sucrose solution at 25 °C for 15–21 days. The mated females had significantly greater longevity than the unmated females, supporting the nuptial gift hypothesis. Body size also affected the survival period. 4. The results suggest that the nuptial gift is an important factor for the evolution of pre‐overwintering copulation in species in which females mate both before and after overwintering.     

Mortality during dispersal and the cost of host-specificity in parasites: how many aphids find hosts?

1. For a full assessment of explanations for the evolution of host-specificity it is necessary to estimate the probability that a dispersing parasite finds a host. We develop a method of estimating this success rate from samples of dispersing parasites and populations resident on hosts.
2. Applying this method to data on the bird cherry-oat aphid, Rhopalosiphum padi (L.), from southern Scotland in 1984–92, we estimate that 0·6% of the autumn migrants find hosts.
3. With such a low success rate, there should be selection for a broadening of host range, to include any host on which the colonist's fitness is more than about 0·6% of that on the normal hosts. We argue that neither nutrition nor the need for 'enemy-free space' are sufficient explanations of the host-specificity of this animal, and propose instead that it is the host's role as a rendezvous for mating that constrains the migrants to their costly host-specificity.
4. We also discuss the implications of this low success rate for the hypothesis that aphids speciate sympatrically through the formation of host races.     

Effects of soil humidity on respiration and frost resistance during winter diapause in the pine beauty moth,Panolis flammea

1. Panolis flammea is an important pest whose populations intermittently outbreak in Europe. The species overwinters as pharate moths in the pupal stage in soil.
2. Details on the metabolic activity and cold hardiness of P. flammea during the overwintering period have not been published. Therefore, we assessed O₂ consumption and the supercooling point (SCP) of P. flammea in late November, mid-February, and mid-March and the influence of soil humidity under fluctuating temperatures and with brief exposures to two increased temperature regimes (10 and 20°C).
3. The respiration pattern indicated diapause termination in mid-February. A threshold of 0.169 μl O₂ h⁻¹ mg⁻¹ fresh weight indicated potentially activated pre-emerging moths. Drought increased respiration rates.
4. The SCP was lowest in mid-February (−22.2°C) and was negatively correlated with pupal mass. The frost tolerance tended to increase with low substrate humidity, especially at the end of the overwintering period.
5. Our results indicate that P. flammea requires more energy during dry and mild winters than in wet and cold winters. Winter diapause termination and post-diapause development may therefore be accelerated as environmental warming and drought increase.

     

Cold hardiness of the overwintering black carpenter ant

Abstract Cold hardiness was investigated in overwintering field nests of the black carpenter ant Camponotus pennsylvanicus (De Geer) in the Commonwealth of Virginia. No active nest thermoregulation was observed: temperatures of galleries, worker bodies, worker clusters, and larval clusters were within 3°C of ambient temperature. Nest temperatures generally fluctuated less rapidly and severely than did ambient temperature; thus, the nest afforded protection from potentially fatal sudden temperature drops. Glycerol, the only polyol cryoprotectant detected, was found in all castes and larvae. Supercooling points were low and ranged from ? 17°C in major workers to ?22°C in larvae. A second heat release peak, occurring around ? 8°C, was seen in all adults, but it was not observed in larvae. This higher temperature peak in adults probably represents the freezing of the gut contents, as adults were found to overwinter with the crop full or partially full. Larvae did not overwinter with liquid food in the gut.     

Life-cycle variation in the aphid Sitobion avenae: costs and benefits of male production

Abstract 1. Patterns of male production and life-cycle variation were investigated in the aphid Sitobion avenae . Seventy-seven field-collected clones were subjected to a 14 °C short day-length regime to assess their reproductive modes, and three clones were used to study life-cycle inheritance. A further analysis assessed the cost of male production.
2. In comparison with those from East Anglia, there were more holocyclic and intermediate clones found in Scottish populations, and they produced significantly more mating females. In total, 44% of clones were androcyclic.
3. The inheritance of life cycle showed a greater level of complexity than could be achieved by previously suggested monohybrid inheritance mechanisms.
4. Holocyclic and intermediate clones produced a higher proportion of males than did androcyclic clones. Inter-clonal differences were reflected in the pattern of male production in the reproductive sequence.
5. A significant cost was associated with male production in terms of a reduction in both fecundity and total offspring biomass.
6. Winged females rarely gave birth to males but the pattern of mating female production differed between holocyclic and intermediate clones.
7. Patterns of male and mating female production by the different types of clone may be related to different advantages and disadvantages of dispersal and inbreeding.
8. Recent models of aphid overwintering could be enhanced by consideration of issues raised in this study, such as the cost of male production, the inheritance of life cycle, and the patterns of sexual morph production.     

Overwintering microhabitat selection by an Endoparasitoid (Hymenoptera: Aphidiidae): Induced phototactic and thigmokinetic responses in dying hosts

Aphidius nigripesAshmead, an endoparasitoid of the potato aphid, Macrosiphum euphorbiae(Thomas), not only has the ability to modify host behavior, but does so differently depending on its physiological state. A previous study indicated that just prior to death, parasitized aphids that contain diapausing parasitoid larvae leave the host plant to mummify in concealed sites, while those containing nondiapausing parasitoids generally remain on the plant. This study explored the proximal factors involved in the selection of an overwintering microhabitat by a host containing a diapausing A. nigripeslarva. Parasitized aphids showed negative phototaxis, thigmokinesis, and chose a dark rather than a light-colored substrate when seeking a site to mummify. However, their behavior was not influenced by either gravity or the presence of another mummy. The combined effects of these behavioral patterns would result in dormant parasitoids overwintering in sheltered sites, thereby reducing the negative effects of adverse climatic conditions and the actions of natural enemies. The utilization of these proximal cues may also enhance parasitoid, survival by reducing aphid wandering time prior to mummification.