斑痣悬茧蜂寄主搜索中的学习行为

利用风洞技术研究了斑痣悬茧蜂不同阶段的经历对其寄主甜菜夜蛾搜索行为的影响.结果表明:寄生蜂幼期发育到羽化早期所经历的植物对其成虫搜索行为具有一定的影响,在供试的大豆、棉花和白菜等3种植物中,只有大豆-寄主幼虫复合体对无经验寄生蜂的行为反应具有显著影响.寄生蜂1次产卵经历对后续搜索行为的影响取决于饲养寄主幼虫的植物种类,只有在大豆和白菜上的产卵经历对后续搜索行为产生显著影响,即明显偏好经历过的植物;对于在不同植物上经历2次产卵的寄生蜂,后续搜索行为反应取决于植物种类及其顺序,若2次产卵经历发生在大豆与白菜之间,无论顺序先后,后续行为反应均偏好大豆-寄主幼虫复合体;但若2次产卵经历发生在大豆与棉花之间,只有当第2次为大豆时,后续行为反应显著偏好大豆-寄主幼虫复合体;若2次寄生经历发生在棉花与白菜之间,只有当第2次经历为白菜时,后续行为反应显著偏好白菜-寄主幼虫复合体.根据研究结果推断,斑痣悬茧蜂幼期发育、成虫早期羽化的经历、成虫产卵经历对后续搜索行为具有显著影响,而且这种影响与寄主幼虫的食料植物有关.     

寄生蜂调控寄主害虫免疫与发育机理的研究新进展

寄生蜂是重要且种类最为丰富的膜翅目昆虫类群之一,也是极具价值的害虫生物控制因子。寄生蜂携带有不同类型的活性因子,包括毒液、多分DNA病毒类病毒颗粒、卵巢蛋白、畸形细胞及幼虫分泌物等,用于调控寄主害虫的免疫反应、发育等重要生理过程,以确保成功寄生并确保其子代在寄主害虫体内(内寄生蜂)或体表(外寄生蜂)正常发育,最终可导致寄主害虫死亡,从而有效控制寄主害虫种群数量。目前已有诸多与寄生蜂调控寄主害虫内在机理相关的研究报道,该领域也已成为昆虫寄生学与生理学的研究热点之一。本文仅从寄生蜂寄生因子多样性、寄生蜂调控寄主害虫免疫及发育的机理等方面,对相关的最新研究进展作一概述。     

生物因子对寄生蜂滞育的影响

在影响寄生蜂滞育的生物因子中,寄主及亲代是主要影响因子。寄主可以从种类、类型、生理状态及丰富度等方面影响寄生蜂的滞育:寄生不同种类的寄主,寄生蜂的滞育反应、滞育进度、滞育比例以及光周期反应表现等均有不同;寄主类型的影响在蚜茧蜂类群中表现最为突出,不同寄主类型能对蚜茧蜂的滞育诱导产生不同影响;此外,寄主生理状态和寄主丰富度也是影响寄生蜂滞育的重要因子。亲代对寄生蜂滞育的影响则通过其所经历的环境条件以及自身因素等方面来表现:亲代经历的光周期和温度等能显著影响子代的滞育,甚至起完全决定作用;在亲代自身因素的影响中,亲代虫龄差异是主要因素。本文同时对寄生蜂滞育的研究及应用前景也一并作了展望。     

寄生蜂取食寄主特性及其在害虫生物防治中的作用

许多寄生性天敌昆虫的雌虫不仅寄生寄主, 而且还能取食寄主。在卵育型（synovigenic）寄生蜂类群中, 取食寄主行为是较为普遍的现象。本文综合近20年相关研究进展, 从寄生蜂类群、取食类型、生态学意义及影响因子等方面对寄生蜂的取食寄主行为进行了归纳总结。寄生蜂通过取食不仅可以杀死寄主, 直接起到控制害虫种群数量的作用, 还能通过取食策略为卵的成熟和再生提供营养来源, 对延长雌虫的寿命也有一定的帮助。对取食寄主行为的了解可为筛选优势寄生性天敌种类、评估寄生蜂在害虫生物防治中的作用提供重要信息。     

寄生蜂寻找隐蔽性寄主害虫的行为机制

林木蛀干类害虫具有高度的隐蔽性,是林业上的一类重要害虫,也是目前世界上最难防治的害虫类群之一.寄生蜂在与寄主长期的协同进化过程中,形成了搜索、发现和攻击寄主害虫的独特机制,能够有效地找到并寄生它们.总结了寄生性天敌寻找、发现并成功定位隐蔽性寄主害虫的行为学机制.寄生蜂可以利用来自嗅觉的化学信息物质(如寄主、寄主粪便、虫道共生菌的挥发性气味)、寄主成虫的化学通讯物质、来自视觉的植物表面色差信息、来自触觉的寄主保护物性状特征、来自寄主取食和运动所产生的介质振动信号以及来自寄主活动和代谢的红外辐射等多种途径有效地发现隐蔽性害虫的位置,从而完成寄生行为.有些寄生蜂还能综合利用来源不同的多种信息,从而提高寄主定位的可靠性和准确性.本文还对寄生蜂寻找寄主的这些线索在生物防治上可能的利用途径和前景进行了讨论.这对促进我国在该领域的研究,充分利用天敌昆虫,提高生物防治效率具有参考价值.     

白蜡吉丁肿腿蜂学习行为的研究

肿腿蜂是防治林木蛀干害虫的重要天敌。为了解肿腿蜂搜索寄主的行为机制,研究了白蜡吉丁肿腿蜂Sclerodermus pupariae Yang et Yao搜索和寄生我国重大林木蛀干害虫——栗山天牛Massicus raddei(Blessig)幼虫过程中的学习行为。结果表明,白蜡吉丁肿腿蜂的记忆效应随着搜索次数的增加而增加。用寄主虫粪和木屑混合物预处理后,白蜡吉丁肿腿蜂搜索到寄主的时间缩短。不同学习经历的白蜡吉丁肿腿蜂对与寄主栗山天牛相关的气味源物质嗅觉测定结果表明,白蜡吉丁肿腿蜂经历栗山天牛幼虫虫粪和蛀屑环境后明显倾向于选择栗山天牛虫粪和木屑混合物,而经历栗山天牛幼虫或辽东栎树皮环境的肿腿蜂对相应的气味选择偏好性不显著。研究结果表明,多寄主型寄生蜂白蜡吉丁肿腿蜂具有较强的联系性学习能力有利于用来防治多种非原始寄主害虫,能够明显提高其对新寄主的寄生作用。     

木虱啮小蜂对枸杞、枸杞木虱的行为反应

木虱啮小蜂Tetrastichus sp.是枸杞木虱Paratrioza sinica Yang & Li若虫外寄生蜂,是控制枸杞木虱种群数量动态的重要因子之一。为查明其寻找寄主的信息素,应用四臂嗅觉仪、培养皿两种方法测定了枸杞Lycium barbarum L.的健康叶、虫伤叶、枸杞木虱若虫、若虫与叶复合体、卵与叶复合体和若虫分泌物等不同物质对木虱啮小蜂行为反应的影响。结果证明枸杞木虱若虫分泌物对木虱啮小蜂有明显的吸引作用,四臂嗅觉仪测定时有73%的雌蜂趋向分泌物材料区（P=0.0000）。枸杞健康叶, 虫伤叶及其水、正丁烷提取物, 卵与枸杞叶复合体对木虱啮小蜂无明显吸引作用。木虱若虫水提物及正丁烷提取物在培养皿中可吸引木虱啮小蜂并可引起刺探行为,但嗅觉仪测定时单独若虫并不吸引木虱啮小蜂,只有活体若虫与枸杞叶片复合体才对木虱啮小蜂有吸引作用（P=0.0004）。木虱啮小蜂通过与寄主若虫的接触,可提高其搜索效率。接触过寄主若虫的雌蜂第一次找到寄主的时间显著少于未曾接触寄主若虫的雌蜂,前者只用后者1/4的时间,说明该寄生蜂能对其寄主若虫进行学习。     

拟寄生蜂搜索产卵过程中对寄主的竞争

综述拟寄生蜂搜索产卵过程中对寄主竞争的最新研究进展.这类竞争具有四种方式,即标记寄主、杀卵和杀幼、守护寄主和捕食寄主.（1）标记寄主常涉及寄主标记信息素,这是由雌蜂在产卵前、产卵时或产卵后分泌的化学物质.寄主标记信息素常介导拟寄生蜂对已寄生和健康寄主的辨别、减少过寄生和多寄生、减轻种内和种间竞争压力.（2）雌蜂遇到已寄生寄主时,很多种类杀死前一雌蜂遗留的卵和幼虫,再产下自己的卵.雌蜂使用三种方法杀卵和杀幼,即产卵器穿刺、取食和使用有毒物质.通过杀卵和杀幼,产卵雌蜂清除了前一雌蜂遗留的后代,主动改善了寄主品质,从而有利于自身后代的生存.（3）守护寄主在肿腿蜂科、缘腹细蜂科、金小蜂科、缨小蜂科和茧蜂科中均有报道,守护者驱逐入侵者以保护后代及健康寄主.（4）捕食寄主不仅减少了健康寄主数量,且直接导致已寄生寄主中拟寄生蜂卵和幼虫的死亡.雌蜂一般在体内成熟卵量较少时捕食寄主.讨论了研究拟寄生蜂搜索产卵过程中竞争寄主的理论意义和实际应用价值.     

农业景观格局与麦蚜密度对其初寄生蜂与重寄生蜂种群及寄生率的影响

农业景观格局与过程能够强烈影响寄生蜂对寄主的寻找及寄生作用,寄主密度亦是影响寄生蜂分布的重要因素,然而农业景观的格局和寄主密度对寄生蜂寄生率的相互影响是一项值得研究的工作.在简单与复杂2种麦田农业景观结构下,调查了麦蚜的分布格局与2种寄主密度下麦蚜的初寄生率与重寄生率,分析了景观结构对麦蚜密度的影响、景观格局与麦蚜密度对寄生蜂寄生率与重寄生率的影响及交互作用.结果表明:景观结构的复杂性对麦蚜分布和寄生蜂初寄生率与重寄生率的影响均不明显,但寄主密度与景观结构的复杂性对寄生蜂的影响存在着明显的交互作用,寄主密度与寄生率呈正相关,寄主密度较低时烟蚜茧蜂为优势种,寄主密度较高时燕麦蚜茧蜂为优势种.麦蚜初寄生蜂与重寄生蜂对寄主密度的反应与其形态学、体型大小以及生活史特征相关,初寄生蜂与重寄生蜂的群落组成显著影响其对麦蚜的寄生率,而与景观结构的复杂性关系不大.     

用替代寄主繁殖的川硬皮肿腿蜂的学习行为

采用Y型嗅觉仪进行双向选择实验,研究了用替代寄主黄粉虫蛹繁殖的川硬皮肿腿蜂寄主搜索过程中的学习行为。结果表明,川硬皮肿腿蜂羽化期和成虫初期经历松枝皮、松针、松节油、杉枝皮等的挥发物后,雌蜂对这些挥发物的选择性明显提高,但对杉叶挥发物无明显的学习行为。羽化期和成虫初期是否投放新鲜寄主,对雌蜂的气味选择性没有明显的影响。成蜂取食黄粉虫蛹和蜂蜜时均可联系性学习松枝和杉枝气味。取食并经历杉枝和松枝挥发物4天和8天的寄生蜂之间对相应气味的选择性无显著差异。     

How host plant variability influences the advantages to learning: a theoretical model for oviposition behaviour in Lepidoptera

Learning can allow individuals to increase their fitness in particular environments. The advantage to learning depends on the predictability of the environment and the extent to which animals can adjust their behaviour. Earlier general models have investigated when environmental predictability might favour the evolution of learning in foraging animals. Here, we construct a theoretical model that predicts the advantages to learning using a specific biological example: oviposition in the Lepidoptera. Our model includes environmental and behavioural complexities relevant to host selection in these insects and tests whether the predictions of the general models still hold. Our results demonstrate how the advantage of learning is maximised when within-generation variability is minimised (the local environment consists mainly of a single host plant species) and between-generation variability is maximised (different host plant species are the most common in different generations). We discuss how our results: (a) can be applied to recent empirical work in different lepidopteran species and (b) predict an important role of learning in lepidopteran agricultural pests.     

Nectar provisioning close to host patches increases parasitoid recruitment,retention and host parasitism

In the adult stage, many parasitoids require hosts for their offspring growth and plant-derived food for their survival and metabolic needs. In agricultural fields, nectar provisioning can enhance biological control by increasing the longevity and fecundity of many species of parasitoids. Provided in a host patch, nectar can also increase patch quality for parasitoids and affect their foraging decisions, patch time residence, patch preference or offspring allocation. The aim of this study was to investigate the impact of extrafloral nectar (EFN) provisioning close to hosts on parasitoid aggregation in patches. The aphid parasitoid Diaeretiella rapae (M’Intosh) was released inside or outside patches containing Brassica napus L. infested by Brevicoryne brassicae L. aphids and Vicia faba L. with or without EFN. When parasitoids were released outside patches, more parasitoids were observed in patches with EFN than in patches deprived of EFN. This higher recruitment could be linked to a higher attraction of a combination of host and food stimuli or a learning process. A release–recapture experiment of labeled parasitoids released within patches showed the higher retention of parasitoids in patches providing EFN and hosts, suggesting that food close to the host patch affects patch residence time. Both attractiveness and patch retention could be involved in the higher number of parasitoids foraging in host patches surrounded by nectar and for the higher parasitism recorded. Nectar provisioning in host patches also affected female offspring allocation inside the patch.     

Early experience influences several steps of the host selection process differentially in Aphidius ervi (Hymenoptera,Braconidae)

Experience of host-associated olfactory stimuli during development affects subsequent foraging decisions in many parasitoids, leading to host fidelity. We have recently shown that odours emitted by an alien host-plant complex (HPC) may affect this learning process. However, the consequences of this olfactory experience on parasitoid host foraging decisions is unknown. Here, we investigated if olfactory preferences induced by experience might drive parasitoid HPC choice and oviposition decisions. We presented two HPCs in dual choice experiments to Aphidius ervi females that had been reared on each HPC, either in a simple (one HPC) or complex (two HPCs) olfactory environment. HPC choice, time before landing on a HPC and number of aphid attacks were recorded. Early experience had contrasting effects on each of these parameters. Regardless of their origin, parasitoids did not land preferentially on any HPC, but they more frequently attacked one of the two hosts (Acyrthosiphon pisum) once they had landed on its HPC. Females emerging from the A. pisum/faba bean HPC attacked more aphids, regardless of the host species. Finally, the olfactory complexity of the environment had inconsistent effects on foraging decisions. These observations, contrasting with previous results obtained in olfactometer assays, indicate that olfactory preferences induced in early stages are not sufficient to predict parasitoid oviposition decisions. Moreover, the integration of multiple signals at several scales might generate different foraging patterns at each step of the host selection process.     

Aphid parasitoid responses to semiochemicals — Genetic, conditioned or learnt?

Parasitoid foraging behaviour is known to be influenced by interactions of genetic, physiological, environmental and experiential factors. Although the role of genetics, learning and conditioning in determining responses to foraging cues has been studied in lepidopteran parasitoids, aphid parasitoids have been less intensively researched. Using the tritrophic system,Vicia faba — Acyrthosiphon pisum — Aphidius ervi, evidence for the role of genetics and learning in parasitoid foraging is presented, and the difficulty of differentiating between genetic responses and those conditioned during parasitoid development is discussed. Aphidius ervi responds to aphid sex pheromones both in the field and in the laboratory. Since laboratory reared individuals have never experienced sexual aphids, the response must be genetic as it cannot have been conditioned during development. An example of a response conditioned during development is the variable response ofA. rhopalosiphi to different wheat cultivars depending upon host feeding. Aphid parasitoids also are adept at learning as shown by their responses to plant-derived cues which are learnt as Conditioned Stimuli (CS). Host products such as honeydew, as well as the host itself, can act as the Unconditioned Stimulus (US) in the learning process. Aphidius ervi offers a good model for investigating the role of these factors in parasitoid foraging behaviour. Finally, the value of such research for biological control programmes involving aphid parasitoids is discussed.     

Density‐mediated indirect interactions alter host foraging behaviour of parasitoids without altering foraging efficiency

1. Foraging decisions of parasitoids are influenced by host density via density‐mediated indirect interactions. However, in the parasitoid's environment, non‐suitable herbivores are also present. These non‐hosts also occur in different densities, which can affect a parasitoid's foraging behaviour. 2. The influence of non‐host densities can be expressed during the first phase of the foraging process, when parasitoids use plant volatiles to locate plants infested by their host. They may also play a role during the second phase, when parasitoids use infochemicals from the host and plant to locate, recognise and accept the host. 3. By using laboratory and field setups, it was studied whether the density of non‐host herbivores influences these two phases of the foraging behaviour of the parasitoid Cotesia glomerata as well as the parasitoid's efficiency to find its host, Pieris brassicae caterpillars. 4. The findings show that a high non‐host density, regardless of the species used, negatively affected parasitoid preference for host‐infested plants, but that the behaviour on the plant and the total host‐finding efficiency of the parasitoids were not influenced by non‐host density. 5. These results are discussed in the context of density‐mediated indirect interactions.     

半闭弯尾姬蜂寄主搜索中的学习行为

研究了半闭弯尾姬蜂寄主搜索过程中的学习行为。结果表明,成虫期之前的饲养寄主所取食的寄主植物对成蜂行为没有影响,而雌蜂早期的短暂经历可对其随后的行为反应产生显著影响,从而对已经历的植物气味表现出显著的嗜好,但这种通过学习所表现出的嗜好又可因新的经历而改变。雌成蜂不仅能对其所经历的虫伤寄主植物释放的信息化合物进行学习,而且对其所经历的寄主幼虫的信息化合物也能进行学习。     

Host kairomone learning and foraging success in an egg parasitoid: a simulation model

Abstract 1. Trissolcus basalis (Wollaston) (Hymenoptera: Scelionidae) is an egg parasitoid that recognises chemical residues left by its host the green stink bug Nezara viridula (L.) (Heteroptera: Pentatomidae) as kairomone signals, enabling it to find egg masses in which to lay eggs. 2. Kairomones are usually present as patches deposited by N. viridula females, and recent results (Peri et al., Journal of Experimental Biology, 209 , 3629–3635, 2006) indicated that females of T. basalis are able to learn the features of their foraging environment and to adjust accordingly the amount of time spent on the patches of kairomones they are visiting, depending on whether or not host eggs are found. 3. In order to assess the impact of this learning ability, a Monte Carlo, spatially explicit and individual‐based simulation model was built to quantify the foraging efficiency of T. basalis females in environments with different levels of host abundance and distribution. In all cases, the present study compared the foraging efficiency of simulated T. basalis females having the ability to learn with those lacking this ability. 4. Learning females always visited a higher number of kairomone patches and attacked a higher number of hosts than non‐learning females, especially when there was a high density of kairomone patches in the environment. 5. Learning ability globally appears to allow the maintenance of efficient foraging success, especially when there is a low probability for the kairomone patches to contain discoverable hosts. 6. The increase in foraging efficiency for learning females appears to depend on the characteristics of the habitat in which they are foraging. Results thus suggest that significant variation in learning ability is likely to occur in natural wasp populations facing different environments with different host spatial distributions.     

Patch exploitation strategies of parasitoids under indirect intra‐ and inter‐specific competition

1. Insect parasitoids are expected to evolve behavioural strategies to exploit resources in competitive environments optimally. Indirect competition between parasitoids is particularly common because exploited host patches remain available in the environment for other foraging individuals. 2. The effects of indirect competition on the behaviour of two closely related generalist egg parasitoids were investigated: Trichogramma pintoi Voegelé and Trichogramma minutum Riley (Hymenoptera: Trichogrammatidae). Patch residence time, a patch‐leaving mechanism, and progeny sex allocation of females foraging were analysed: (i) alone, (ii) in patches partially parasitised by conspecifics, and (iii) in patches partially parasitised by heterospecifics. 3. Each species responded differently to indirect competition. Trichogramma pintoi females shortened their patch residence times, but they did not adjust their progeny sex ratios. In contrast, T. minutum females did not modify their patch residence times, but they did increase their progeny sex ratios in response to competition. Both Trichogramma species used host rejection, either by antenna rejection or by ovipositor rejection, as a patch‐leaving mechanism. 4. In agreement with a companion study of direct competition using the same model species, the present results indicate that even amongst closely related species, responses to competition can vary considerably.     

Learning in the Generalist Tachinid Parasitoid Exorista Mella Walker (Diptera: Tachinidae)

Many parasitoids have been shown to learn visual and/or olfactory cues associated with hosts. In contrast to the Hymenoptera, learning in dipteran parasitoids is relatively unstudied. This study explores the ability of a polyphagous tachinid, Exorista mella, to learn to associate visual and olfactory cues with hosts. In an experiment involving colored host models, flies trained on models of one color were subsequently attracted more strongly to models of the color that they had not experienced. The unsuitability of these models as hosts suggested that the flies may have engaged in avoidance learning. Flies demonstrated the ability to learn to associate colored disks with hosts. A separate experiment demonstrated that flies responded to volatile plant compounds but failed to find evidence for odor learning. Learning of host-associated cues by E. mella may allow this generalist parasitoid to take advantage of locally abundant host populations and maintain host-searching efficiency in an environment.     

Importance of host feeding for parasitoids that attack honeydew-producing hosts

Insect parasitoids lay their eggs in arthropods. Some parasitoid species not only use their arthropod host for oviposition but also for feeding. Host feeding provides nutrients to the adult female parasitoid. However, in many species, host feeding destroys an opportunity to oviposit. For parasitoids that attack Homoptera, honeydew is a nutrient‐rich alternative that can be directly imbibed from the host anus without injuring the host. A recent study showed that feeding on host‐derived honeydew can be an advantageous alternative in terms of egg quantity and longevity. Here we explore the conditions under which destructive host feeding can provide an advantage over feeding on honeydew. For 5 days, Encarsia formosa Gahan (Hymenoptera: Aphelinidae) parasitoids were allowed daily up to 3 h to oviposit until host feeding was attempted. Host feedings were either prevented or allowed and parasitoids had ad libitum access to honeydew between foraging bouts. Even in the presence of honeydew, parasitoids allowed to host feed laid more eggs per hour of foraging per host‐feeding attempt than parasitoids that were prevented from host feeding. The higher egg‐laying rate was not compromised by survival or by change in egg volume over time. In conclusion, host feeding can provide an advantage over feeding on honeydew. This applies most likely under conditions of high host density or low extrinsic mortality of adult parasitoids, when alternative food sources cannot supply enough nutrients to prevent egg limitation. We discuss how to integrate ecological and physiological studies on host‐feeding behavior