Changes in abundance of Vespula germanica and V. vulgaris in England

1. Thirteen time series, varying from 17 to 27 years, of the abundance of Vespula germanica and V. vulgaris from lowland England are examined. The time series depend on either spring queens and workers taken in Malaise or suction traps, or collected colonies. 2. During the late 1970s and early 1980s, the abundance of V. germanica declined abruptly but that of V. vulgaris did not. 3. During the early 1980s, the 2‐year cycle of annual abundance of V. vulgaris changed to a nearly perfectly damped pattern of annual abundances. 4. The most likely factor causing these population changes was the increased use of pesticides acting directly by killing the wasps and indirectly by reducing their food resources. 5. The difference in response of the two species to increased pesticide use may be related to a difference in foraging ability.     

Subaqueous hydrochory: open‐channel hydraulic modelling of non‐buoyant seed movement

1. Subaqueous transport may be a significant dispersal and migration mechanism of non‐buoyant seeds of aquatic and riparian plants, and also secondary transport of seeds once they have lost buoyancy, but the efficiency of this difficult to observe process is largely unexamined. This study uses hydraulic modelling to establish the discharges that move the non‐buoyant seeds of Hymenocallis coronaria as bedload or suspended load; uses stream gauge data to examine the frequency of effective discharges from late June to late September, the seed maturation and germination period; and the potential transport distance of the seeds. 2. The results show that the majority of non‐buoyant seeds of H. coronaria can be transported as bedload through entire modelled stream reaches of lengths 10.8, 18 and 14.4 km with the 0.5 year return interval flow. Bedload apparently has the ability to move seeds over great distances, and may be a substantial factor determining the genetic structure, demography and dynamics of populations and communities. However, prolonged movement of non‐buoyant seeds in suspension appears to be quite rare. 3. Although insect mediated pollination and biochory occur concurrently with bedload transport, bedload transport alone may be sufficient to account for the established gene flow rate of H. coronaria. The potential transport distance of many of the seeds exceed that between populations, and migration may occur more frequently than the species’ generation time. 4. This is the first known study to use open‐channel hydraulic modelling and sediment transport analysis to determine the effectiveness of non‐buoyant seed transport. This method of analysis shows promise for application in other contexts, and especially where flow management is a critical issue for maintenance of rare species.     

悦目金蛛拖丝的超微结构研究

采用非固定的抽丝方法,从一只未麻醉的悦目金蛛(Argiope amoena)的纺器将拖丝抽出,然后用扫描电镜(SEM)对拖丝进行超微结构的观察,结果表明:悦目金蛛拖丝至少具有2根、3根、4根及多根单丝纤维构成的4种不同结构,其中有一种类似弹簧的结构;另外,丝的表面还出现一种小环结构,这两种结构可能是拖丝纤维具有优良机械性能的原因之一。"束状结构"和"小环结构"在文献中未见报道。拖丝的直径范围为0.25~10.77μm;悦目金蛛似乎能调节拖丝的结构和直径,以适应其所面临的即时环境。本文基于上述观察结果并结合前人的研究,提出了蜘蛛拖丝结构-生物学功能多样性假说,对蜘蛛丝的结构与生物学功能之间的关系作了探讨。     

Natural mortality factors of Leucoptera coffeella (Lepidoptera: Lyonetiidae) on Coffea arabica

The natural mortality of the coffee leafminer, Leucoptera coffeella (Guérin-Méneville) was investigated in three strata of coffee plant canopy for three seasons through construction and analysis of ecological life tables. Mortality of the leafminer was similar on all thirds of the canopy. Total mortality of immature stages was 95%, with 38.5, 43.8 and 12.7% occurring during egg, larval, and pupal stages. Rainfall killed 39.3% of eggs and larvae, and together with egg inviability (16.3%) and Vespidae (11.3%), were the highest mortality factors. Six wasp parasitoids caused 8% of larval mortality. Egg and larva were the critical stages. Variation in mortality was primarily associated with egg inviability, rainfall, and parasitism by Horismenus sp. (Hymenoptera: Eulophidae). Physiological disturbances during molting and metamorphosis also contributed for fluctuations in mortality of the leafminer. Tactics of integrated pest management to enhance natural mortality of the leafminer while conserving or augmenting the action of natural enemies are discussed.     

帚状漏斗蛛模式标本的再研究(蜘蛛目:漏斗蛛科)

本文重新描述了保存于湖南省生物研究所的帚状漏斗蛛Agelena scopulata Wang, 1991的模式标本,并提供了鉴别特征及生殖器官形态结构图。     

皱胸尖裂姬蜂对机敏异漏斗蛛的拟寄生行为及其发育特征

寄生蜂是蜘蛛的主要天敌类群之一,但寄生于漏斗蛛的寄生蜂种类较少,且缺乏相关寄生蜂的详细研究报道。我们研究了皱胸尖裂姬蜂(Oxyrrhexis rugosus)对机敏异漏斗蛛(Allagelena difficilis)的拟寄生,旨在揭示蜘蛛寄生蜂的拟寄生行为及其发育特征。显微镜下观察了12头机敏异漏斗蛛头胸部背面的皱胸尖裂姬蜂卵,并以均值法统计了皱胸尖裂姬蜂各发育阶段的历期,进一步观察了皱胸尖裂姬蜂寄生机敏异漏斗蛛后对寄主的影响。交配后的雌性皱胸尖裂姬蜂经过寻找、降落、蛰刺蛛体后伺机将卵产在机敏异漏斗蛛的头胸部背面后部;孵化后的皱胸尖裂姬蜂幼虫头部形成一个特殊摄食导管,通过摄食导管获取蛛体的营养;幼虫随着龄期增长,体色由浅变深,历期约10 d;幼虫老熟后在蛛网的漏斗状管道内结茧化蛹,蛹期约为12 d;成体雌、雄蜂寿命约为11 d,皱胸尖裂姬蜂的平均生活史周期约为33 d。皱胸尖裂姬蜂寄生后对寄主蜘蛛的行为和生活状态造成了严重的影响,随着幼虫龄期增长被寄生机敏异漏斗蛛不再进食、蜕皮,活动减少,蛛体逐渐萎缩,直至老熟幼虫离开蛛体时,蜘蛛死亡。该研究不仅增加了漏斗蛛寄生性天敌的已知种类,而且初步了解了以漏斗蛛为寄主的姬蜂的产卵行为、后代的发育特征以及对寄主蜘蛛的影响,这将为研究蜘蛛寄生蜂及其与寄主蜘蛛之间的化学通讯和协同进化提供重要的基础资料。     

季节变化对聚果榕-榕小蜂互利共生系统生长与繁殖的影响

榕属植物及其传粉昆虫榕小蜂是自然界协同进化的经典模型,榕果内雌花资源如何分配一直是备受关注的问题。为验证季节变化对榕树-榕小蜂互利共生系统生长与繁殖的影响,该研究以西双版纳地区的聚果榕(Ficus racemosa)为材料,分析了季节变化对榕果大小、自然进蜂量以及榕树-榕小蜂繁殖的影响,并利用人工控制性放蜂实验和模型拟合,探讨榕果最适进蜂量及不同季节进蜂量对雌花资源分配的影响。结果表明:季节对榕果直径有显著影响,雨季的榕果直径显著小于干热季和雾凉季;不同季节的自然进蜂量也有显著差别,苞片口对调节进蜂数量有重要作用;季节对榕树-榕小蜂繁殖分配也有影响,雾凉季产生的种子数量和榕小蜂数量均最多;同时人工控制实验和二次抛物线模型拟合结果表明,母代雌蜂数量与种子及榕小蜂后代数量均呈抛物线关系,雌蜂数量过多或过少都对榕树-榕小蜂的繁殖不利,自然进蜂量与拟合的最优进蜂量基本一致。研究结果说明榕果进化出了适应西双版纳地区季节变化的繁殖策略。