“策略”是指生物为适应某些特殊条件而演化形成的结构、生理或行为。寄生蜂的存活和生殖完全依赖于寄主，所以，寄生蜂就成为探究动物生活史进化机理的理想生物。产卵策略是寄生蜂生活史进化的生物学的重要特征之一。绝大多数寄生蜂的性别决定方式为单倍体-双倍体机制，即受精卵发育为雌虫，而未受精卵发育为雄虫，交配的雌性在产卵时可控制子代性别，故性别分配就成为产卵策略的重要决策之一。对于群集寄生蜂来说，还有另一重要决策—窝卵数，即一次产卵的数量。理论和实证研究认为，寄主质量（主要是体型大小）以及同种雌蜂的竞争是群集寄生蜂产卵决策的主要依据，但对其他生态和生理因素的影响较少关注，即使提及这些因素的影响，也常常局限于理论模型的预测，而少有实证研究的支持。对此，本研究以群集寄生性蝶蛹金小蜂Pteromalus puparum （L.）为模式，在观察子代蜂胚后发育形态和交配行为的基础上，首先验证了寄主质量和竞争对产卵决策的影响，然后重点研究了雌蜂体型大小、交配行为、抱卵量、寄生经历、产卵顺序等若干因素对产卵决策的影响。本研究对于全面理解群集寄生蜂产卵策略具有重要参考价值。研究获得以下主要结果和结论。 1、为详细了解蝶蛹金小蜂的胚后发育过程，详细观察了子代蜂胚后发育不同阶段的外形及其寄主蛹的外部形态。蝶蛹金小蜂胚后发育历时约2周，其中卵期1 d；幼虫历期约7 d。初孵幼虫体透明；胚后第3～6天体积快速增大，然后减缓，体色由绿变黄；胚后第8天进入预蛹，第9～12天蛹淡色，复眼由淡黄变为深红，第13～14天蛹暗黑色，并逐渐带有金属光泽。卵巢管在羽化当天即开始沉积卵黄，并在羽化后1～4 d连续增加直到出现卵吸收，羽化后5～6 d成熟卵量增速不明显甚至略有减少。寄主蛹随子代蜂从卵发育幼虫再到蛹，体色从绿色变为灰褐色再到土黄色。 2、为深入探究雌、雄蝶蛹金小蜂体型大小对交配行为的影响，采用2因素、3水平的析因设计试验，组成9个配对处理组合，观察分析求偶成功概率、求偶时间、雄蜂爬上雌蜂成功概率、交配时间以及交配总历期。雄蜂体型越大，求偶成功率越高，且第2次交配总历期越短；雌蜂体型越大，第1次求偶时间越长，且前2次交配总历期越长。前次交配成功与否影响下次求偶成功性和成功爬上雌蜂的概率。 为揭示配偶剥夺时间长短对交配行为的影响，设置首次交配后间隔不同时间（6 d、10 d或14 d）处理，观察其交配行为。结果表明，随交配间隔时间延长，雄蜂爬上雌蜂的成功率降低，交配时间稍微延长；首次交配成功与否显著影响第2次交配中成功爬上雌蜂的概率以及交配时间长短。 3、为探究蝶蛹金小蜂的卵成熟动态及其影响因素，观察了低温（5℃）和寄生时间长短（0 ~3 h之间每隔30 min）处理对子代蜂卵成熟动态的影响。低温处理被寄生的寄主使子代蜂卵巢管变细，成熟卵量减少，但低温的影响与雌蜂体型大小和日龄有关。低温处理明显减缓卵成熟速率，各日龄期成熟卵量均明显减少；适温下成熟卵量于羽化后第4天到达高蜂，而低温处理下高蜂期延至第7天；随寄生时间（在寄主体上的驻留时间）的增加，3级卵（共4级）比例明显减小，4级卵增加；寄生后2 h，3级卵全部转化为4级卵；大体型雌蜂内4级卵比例明显较少。本研究结果说明，冬季低温对蝶蛹金小蜂卵成熟有不利影响；首次发现蝶蛹金小蜂在有寄主存在时形成4级成熟卵，而此前研究认为最高为3级。 4、为研究母蜂日龄与其他蜂存在（气味）对蝶蛹金小蜂产卵决策的影响，采用2因素多水平的析因试验设计，首先通过试验确定雌蜂获得最长寿命的补充营养，据此设置母蜂日龄水平（5、15、25、35、45和55 d）；气味处理将其他雌蜂含血淋巴的卵巢涂抹于寄主蛹翅芽部位（有、无）。结果表明，雌蜂日龄越大，产卵概率越小，窝卵数与余卵量亦越少，雄性比例显著升高；雌蜂在无气味寄主上产卵的概率显著高于有气味寄主，剩余卵量明显较少；但气味处理对性比无显著影响。研究说明，雌蜂寿命和同类蜂气味可能影响其部分产卵决策。 5、为探究雌蜂抱卵量与寄主大小对产卵决策的影响，采用2因素、3水平的析因试验设计，选择羽化后不同时间（3、4、6 d）设置3个抱卵量水平，将寄主体重设置为大（0.18 g～0.22 g）、中（0.14 g～0.17 g）和小（0.09 g～0.13 g）等3个水平。结果表明：寄生前时间和余卵量随寄主体重的增加而缩短，驻留时间和子代雌蜂体型大小随寄主体重的增加而增加；抱卵量水平越高，余卵量越少，且子代雄性比例随抱卵量水平的提高而增加。研究结果说明，蝶蛹金小蜂可根据自身抱卵量和寄主大小调整其产卵决策行为。 6、为揭示雌蜂体型大小对其产卵决策的影响，在严格控制寄主菜粉蝶蛹体型大小（体重）的情况下，于室内观察了不同体型大小的蝶蛹金小蜂雌蜂的产卵行为，并调查了子代蜂数量（窝卵数）、性比和体型大小的变化。雌蜂在寄主上的驻留时间随其自身体型增大而缩短，但随寄主体重增大而延长。窝卵数和余卵量受到雌蜂体型大小的显著影响，均随雌蜂体型增大而显著增加（P < 0.05）；但子代蜂性比不受雌蜂体型大小的显著影响 (P > 0.05)。子代雌、雄性体型大小均与雌蜂体型大小无关，但子代雌蜂体型随寄主体重增大而增大。结果说明，雌性蝶蛹金小蜂体型大小影响其部分产卵决策。因此，在建立群集寄生蜂产卵决策模型中应考虑雌蜂体型大小这一重要变量因素。 7、为阐明寄生经历和竞争经历对蝶蛹金小蜂产卵决策的影响，采用2因素、多水平的析因试验设计，通过在寄生前让雌蜂经历不同的密度(1头/管，2头/管，5头/管)环境设置3个竞争经历水平；通过在寄生前给雌蜂提供1次寄生大寄主（0.18~0.22 g）、小寄主（0.09~0.13 g）、或无寄主的经历设置3个寄生经历水平。结果表明，具有竞争经历雌蜂的寄生前时间缩短（为无竞争处理的63.5%），但具有寄生经历雌蜂的寄生前时间显著长于无寄生经历蜂；与无竞争经历相比，具有弱竞争（密度为2雌/管）经历雌蜂的余卵量明显减少，但具有强竞争经历蜂的余卵量没有显著变化；与无寄生经历蜂相比，具有寄生大体型寄主经历雌蜂的余卵量显著减少，但有寄生小体型寄主经历蜂的余卵量没有显著变化。具有强竞争经历雌蜂的子代蜂性比显著大于具有其他竞争经历雌蜂，具有寄生大型寄主经历雌蜂的子代蜂性比显著大于具有其他寄生经历的蜂。研究结果说明，竞争经历与寄生经历显著影响蝶蛹金小蜂的产卵决策。 8、为探究同类蜂存在和连续寄生对产卵决策的影响，采用2因素、多水平的析因试验设计。采取提供不同访问处理的寄主代表同类蜂存在的3个水平：未被访问（对照）、被同窝蜂访问以及被异窝蜂访问；连续（2次）寄生处理中又包含寄主体型大小因素，从而分为4个水平：小→小、小→大、大→大、大→小。试验结果表明：如果2次寄生均为大体型寄主，则驻留时间显著长于其他体型组合；如果没有其他蜂访问，则雌蜂的驻留时间显著长于有其他蜂存在；此外，寄生组合与寄生顺序互作、寄生顺序与其他蜂访问因素互作，显著影响雌蜂驻留时间。与2次寄生的寄主均为大体型寄主（大-大）相比，雌蜂寄生其他组合寄主后的余卵量都显著增大；与没有其他蜂访问（对照）相比，寄生被异窝蜂访问的寄主后余卵量显著减少；而且寄生组合与其他蜂访问因素之间互作影响余卵量。与“大-大”寄主组合相比，寄生其他寄主组合后的窝卵数均显著减少；与无蜂访问相比，寄生其他蜂访问的寄主后的窝卵数显著减少，而且下次寄生的窝卵数显著少于上次，寄生组合与其他蜂访问处理之间、寄生顺序与其他蜂访问之间互作显著影响窝卵数。雌蜂在同窝蜂访问过的寄主上所产的子代蜂性比显著小于对照，寄生“大-大”寄主组合的性比显著高于其他寄主组合；（5）寄主组合处理对子代雌蜂体型大小有显著影响，但其他蜂访问和寄生顺序没有显著影响，寄生“小-小”组合寄主的子代雌蜂显著小于其他寄主组合，同窝蜂访问处理的子代雄蜂显著小于其他访问处理。研究结果说明，蝶蛹金小蜂的产卵决策不但受到同类蜂存在的影响，而且受到寄主体型大小的影响。 9、为验证连续寄生情况下寄生蜂产卵决策是否仍然符合“寄主大小—质量”假说的预测，连续观察了蝶蛹金小蜂雌蜂羽化后不同时间（第5、9、13或17天）的产卵行为。结果表明：窝卵数随寄生次序的增加而减小；子代蜂性比也随寄生次序增加而微弱降低。

Oviposition strategy is one of important characteristics in life history evolution of parasitoids. Most parasitoids have the system of haplodiploid sex determination, in which fertilized eggs develop into females and the unfertilized into males. For solitary parasitoids, sex allocation constitutes most of oviposition decision. But for gregarious parasitoids, another decision about how many eggs is deposited in a single oviposition—clutch size needs to be made, as well as sex determination. Numerous theoretical and empirical studies show that female parasitoids mainly base their ovipositon decision on host quality (e.g. body size) and competition from conspecifics. Other ecological and physiological factors, however, are less investigated—if they are, most are addressed theoretically—for the role in oviposition decision in parasitoids. The present study, using Pteromalus puparum (L.) as the model system, first observed morphology of post-embryonic development and mating behaviors, then verified the influence of host quality and competition, and finally made an intensive investigation into effects of other factors on oviposition decision, including mother body size, copulation behavior, egg load, parasitization experience, and oviposition sequence. This study provides an important contribution to understanding oviposition strategy in gregarious parasitoids. In what follows, major results and conclusions from this study are summarized. 1．To understand the process of postembryonic development of the gregarious parasitoid in details, external morphology of postembryonic stages of P. puparum and their hosts were described on a day to day basis across 2 weeks. The results indicated that postembryonic development took about 2 weeks. Egg stage lasted for 1 day, and larva ca. 7 days. Neonate larva was clear and grew rapidly with body color from green to yellow during next 3-6 days. Prepupal stage appeared 8 days later in light color and the eyes were from pale yellow to dark red 9-12 days later. Pupa was dark in color with metallic luster on day 13-14. Yolk appeared in ovarioles the same day of adult emergence and increased next few days until oosorption. Mature eggs did not obviously increase or even decrease a little during first 4-5 days after emergence. The host pupa, following the development of progeny parasitoid from egg to larva and then to pupa, varied in color from green to light brown and then to yellowish brown. 2．To investigate in detail the influence of body size on mating behaviors in P. puparum, a factorial experimental design was exercised for two factors with three levels. The body size of male and female was divided into large, medium, and small categories, which resulted in 9 pairs of combination. Observation was made of courtship success, courtship time, climbing success, copulation time, and total mating time. The probability of courtship success increased with male body size, but total mating time decreased with the later. Courtship time of first mating and first two mating increased with female body size. The first mating success influenced next courtship success and climbing success. Total mating time increased with the first copulation time. To examine effects of mate deprivation on mating behavior, time intervals were manipulated as 6, 10 and 14 days after the first mating. The results showed that the success of male climbing on to female (climbing success) decreased and copulation time slightly extended with increase of time intervals. The success of first mating influenced climbing success and copulation time of the second mating. 3．To investigate egg maturation dynamic and influential factors,effects of low temperature treatment of parasitized host pupae and parasitization time (every 30 min from 0 to 3 hours) on egg maturation dynamics were observed. The low temperature treatment (5℃) caused ovariole thinner and less mature eggs, and this influence was dependant on female body size and age. The low temperature treatment reduced maturation speed of eggs and day-specific number of mature eggs. The number of mature eggs peaked at the 7th day under low temperature treatment as opposed to the 4th day under the suitable temperature treatment (residence time on host). Proportion of the 3rd class eggs decreased but that of the 4-class eggs increase with the increase in parasitizing time. All 3rd class eggs turned into 4th class eggs when parasitizing time was beyond 2 h. Females with large body size contained fewer 4th class eggs. The results suggested that low temperature exerted negative influence on egg maturation and the 4th class eggs, first reported in this parasitoid, appeared at the presence of hosts. 4．To assess the influence of female age and presence of conspecifics on oviposition decision, factorial design was used for two factors. Age of female parasitoids was manipulated as 6 levels (every 5 days from 5 to 55 days) based on an exploratory test of longevity under different sugar foods. The factor—presence of conspcifics—was categorized as 2 levels (hosts with or without smearing ovary containing hemolymph). The results showed that likelihood of egg deposition, clutch size and remaining eggs decreased, but male proportion increased, with female age. The likelihood of egg deposition increased, but remaining eggs decreased, when the host was free of materials from other comnspecifics as compared to that when the host received the treatment. Sex ratio of progeny parasitoids was not affected by the treatment of hosts. The results suggested that female age and residues from conspecifics affected oviposition decision. 5．To investigate the influence of egg load and host size on oviposition strategy, a factorial experimental design was exercised for two factors each with three levels. Three egg load levels were set by time after eclosion (3rd , 4th and 6th day) and three levels in body size were set by host weight (large: 0.18g~0.22g; medium: 0.14g~0.17g; small: 0.09g~0.13g).The result shows that pre-parasitizing time decreased, but residence time and female offspring size increased, with increasing host body. Remaining eggs reduced but male proportion increased with egg load levels. Results of the present research suggested that P. puparum could adjust their oviposition strategy according to their own egg load and host size 6．Host body size, one of host quality attributes, is often a major focus of the study of foraging behavior in parasitoid behavioral ecology. But little emphasis was placed on parasitoid body size. To investigate the effects of female body size on oviposition strategy in the gregarious parasitoid, Pteromalus puparum, experiments were conducted in laboratory under the stringent control of host (Pieris rapae pupae) body size to observe the oviposition behavior and examine the changes in the clutch size, sex ratio, and body size of the progeny parasitoids. The residence time of females on host pupae decreased with increase of their body size, but increased with host body size. Larger females gave birth to more offsprings with more eggs reserved after a bout of oviposition. Sex ratio and body size of offspring parasitoids were not affected by female body size, but the body size of female offsprings increased with host body size. The results confirm that female body size may affect part of the oviposition strategy in P. puparum, and should therefore be incorporated into models of oviposition strategies for gregarious parasitoids as an important variable. 7．To investigate into effects of experiences of parasitization and competition on oviposition strategy, a factorial experimental design was performed for two factors with multiple levels. The competition experience was manipulated as three levels by maintaining parasitoids, before exposed to parasitism, at different densities in a glass tube (1, 3, or 5 females/tube). The parasitization experience was produced by having parasitoids parasitize hosts of either of large (0.18~0.22g) or small (0.09~0.13g) body sizes, or without parasization (control). Hosts of medium size （0.14~0.17g）were exposed to testing. The results showed that pre-parasitizing time decreased by 63.5% for parasitoids with competition experiences as long as the counterparts without the experience, but increased for parasitoids with the experience of parasitization as opposed to those with the experience of parasitization. Parasitoids with the experience of weak competition left fewer eggs after a bout of oviposition, as compared to their counterparts without the competition experience. Compared to those without the experience of parasitization, parasitoids with the experience of parasitizing hosts in large body size kept less eggs after about of oviposition, while those with the experience of parasitizing hosts in small body size stored eggs by the same number. Sex ratio of progeny parasitoids increased for parasitoids with the experience of strong competition as opposed to those treated with the other experience levels, and also increased for parasitoids with the experience of attacking hosts in large body size as opposed to those with the other treatments of parasitization. The results suggested that experiences of competition and parasitization can influence oviposition decision in P. puparum. 8．To explore the influence of existence of conspecifics and continuous parasitization on oviposition decision, a factorial experimental design was exercised for two factors (existence of conspecifics and host-size combination exposed to two round of parasitization) with multiple levels. Three levels of conspecifics’ existence were set up by providing hosts that were visited previously by parasitoids from the same clutch, a different clutch, or not visited (control). The host-size combination treatment was manipulated as three levels by pairing hosts in either large or small body size, with four combinations of large→large, large→small, small→large, and small→small, respectively. The residence time was longer on hosts that were not visited previously by conspecifics than on hosts visited. Residence time was longer on the large→large host combination than on the other combination levels, and on the hosts not visited than those visited by conspecifics. Moreover, the analysis found significant interactions between host-size combination and parasitization order and between visit by other parasitoids and parasitization order, for the residence time. Remaining eggs were more for the parasitoids attacking the other host combinations than for the large-large combination, but less for the parasitoids attacking hosts visited by conspecifics than for those attacking hosts not visited. Moreover, host-size combination and visitation were interacted in affecting number of remaining eggs. Clutch size increased for parasitoids parasitizing ‘large-large’ host combination as opposed to those attacking the other host-size combinations. Parasitoids laid a large clutch when attacking hosts were visited by conspecifics as opposed to when the hosts were not visited. The analysis revealed significant interactions on clutch size between host-size combination and parasitization order and between visit by other parasitoids and parasitization order. Sex ratio increased in progeny parasitoids from hosts not visited as opposed to visited by conspeficifics, and from hosts of large-large combination as opposed to the other host-size combinations. Body size of female progeny parasitoids was smaller from the ‘small-small’ hosts than fro the other host-size combinations, and from the hosts visited by conspecifics from the same clutch than from the other clutch or not visited. The results suggested that oviposition decision can be affected not only by the presence of conspecifics but by the body size of the host. 9．To test the applicability of “host size-quality” hypothesis to parasitoids performing continuous ovipsition, female parasitoids were observed for oviposition decision at 5, 9, 13, and 17 days after eclosion. The result showed that clutch size increased, but sex ratio slightly decreased, with progress of oviposition.