对寄生蜂的研究往往集中于那些寄生植食性昆虫的种类，而对捕食性昆虫的寄生蜂生物学、行为和生态学所知甚少。本研究在摸清南京地区七星瓢虫Coccinella septempunctata和异色瓢虫Harmonia axyridis的寄生性天敌种类后，针对以七星瓢虫为寄主的2种幼虫-蛹跨期寄生的近缘啮小蜂—瓢虫啮小蜂Oomyzus scaposus和黄胫啮小蜂O. flavitibialis（暂定名），首先比较了这2种啮小蜂在形态、线粒体基因和寄生生物学特征上的差异，然后探究了这2种啮小蜂在共同利用同一头寄主时的子代分配对策，并深入研究了寄主与自身体型大小对瓢虫啮小蜂的子代分配对策的影响，最后比较了健康与被寄生七星瓢虫的自相残杀和集团内捕食情况。本研究为认识寄生瓢虫的寄生蜂行为生态学提供了新的知识。研究获得以下主要结果和结论。 1.瓢虫寄生性天敌调查及近缘种鉴别 选取南京地区三类干扰程度不同的生境进行调查，共发现8种寄生七星瓢虫的昆虫和2种寄生异色瓢虫的昆虫，并发现寄生性天敌种类和个体数量在人为干扰最少的荒地生境中最多。调查发现，伐蚤蝇（Homalotylus sp.）对异色瓢虫蛹的寄生率（5.31%）最高，啮小蜂对七星瓢虫幼虫寄生率（>15%）最高；除已知的瓢虫啮小蜂Oomyzus scaposus外，新发现一种未知的啮小蜂（暂名“黄胫啮小蜂O. flavitibialis）。经形态、杂交试验和线粒体COI基因核酸序列比较，可初步确认黄胫啮小蜂与已知的瓢虫啮小蜂之间存在明显差异，应为一新物种。以七星瓢虫2龄幼虫为寄主的非选择性寄生观察表明，瓢虫啮小蜂的发育历期（18.48 d）显著长于黄胫啮小蜂（16.46 d），子代窝蜂数（8.9头）显著少于黄胫啮小蜂（11.62头），子代体型（雌蜂：0.47 mm，雄蜂：0.40 mm）显著大于黄胫啮小蜂（雌蜂：0.44 mm，雄蜂：0.36 mm），子代性比（雄性占比= 0.18）和黄胫啮小蜂（0.15）无差异。对七星瓢虫不同龄期幼虫的双选寄生观察结果表明，瓢虫啮小蜂对不同龄期幼虫未表现偏好，但黄胫啮小蜂在1龄与3龄瓢虫之间偏好后者（90%）；当面临1、3龄瓢虫幼虫时，黄胫啮小蜂在寄主上的停留时间显著长于瓢虫啮小蜂。研究结果说明，啮小蜂是七星瓢虫幼虫的优势寄生蜂，瓢虫啮小蜂和黄胫啮小蜂可能是亲缘关系相近的姐妹种。 2.两种啮小蜂的寄主辨别能力与多寄生产卵对策 双选生测结果表明，瓢虫啮小蜂无论是否有寄生经验，都不能辨别出被黄胫啮小蜂寄生的寄主和健康寄主；但有寄生经验的黄胫啮小蜂能辨别出被瓢虫啮小蜂寄生过的寄主与健康寄主。对寄生蜂在寄主体上的停留时间分析结果也支持以上表现。瓢虫啮小蜂寄生1次（完成1次以上刺扎后自动离开寄主）与刺扎1次（完成1次刺扎后人为中断继续刺扎）相比，在窝蜂数和性比上均无显著差异；但黄胫啮小蜂寄生1次与刺扎1次的窝蜂数存在显著差异，前者为后者的1.75倍。两种啮小蜂面对已被对方寄生过的寄主具有不同的子代分配对策：①黄胫啮小蜂有25%的雌蜂（n = 24）接受已被瓢虫啮小蜂寄生过1次的寄主，有71.4%（n = 24）的雌蜂接受被刺扎过1次的寄主，而瓢虫啮小蜂有80.8%（n = 26）或91.3%（n = 23）的雌蜂接受已被黄胫啮小蜂寄生或刺扎1次的寄主；②两种啮小蜂面对已被对方寄生1次的寄主时，所产子代蜂窝蜂数均不受前一蜂产窝蜂数的影响，所产性比不受前一蜂的窝蜂数和性比的影响；③面对已被刺扎1次的寄主时，黄胫啮小蜂所产窝蜂数不受寄主体重和前一蜂产窝蜂数的影响，只受到自身体型大小的影响（正相关），瓢虫啮小蜂所产窝蜂数不受上述任何因素的影响；④两种啮小蜂子代性比不受寄主体重、前一蜂产窝蜂数、前一蜂产性比以及自身体型大小的影响。研究结果说明，黄胫啮小蜂可能具有寄主识别能力，但瓢虫啮小蜂无此能力；两种啮小蜂在对已被对方寄生过的寄主上产卵时，窝卵数和性比决策均不受前一蜂子代分配的影响。 3.瓢虫啮小蜂依赖于体型大小的子代分配策略 为明确七星瓢虫幼虫体型大小和雌蜂体型大小对产卵决策的影响，选择不同体型大小的雌性瓢虫啮小蜂，随机对各龄期不同大小的七星瓢虫幼虫进行寄生。结果表明，小体型雌蜂的寄生成功率随寄主大小的增大而减少，而大体型雌蜂的寄生成功率对不同大小寄主均保持较高的水平。随寄主体型增大，子代蜂发育时间缩短、窝蜂数增大，但子代蜂特征与雌蜂大小无关。寄主大小或雌蜂大小均不影响子代蜂性比，亦不影响子代蜂的体型大小。随窝蜂数增大，性比（雄性比例）增大、发育时间缩短；但子代蜂体型大小不受影响。研究结果表明，小体型雌蜂更愿意选择小体型的寄主，而大体型雌蜂对寄主的体型大小没有选择偏好；当窝蜂数增加时，倾向于产雄性子代。 4.瓢虫啮小蜂寄生对七星瓢虫幼虫应对自相残杀和异色瓢虫捕食的影响 为明确啮小蜂寄生是否影响七星瓢虫幼虫的种内（自相残杀）和种间（集团内捕食）捕食行为，在培养皿内引入被寄生和健康的七星瓢虫4龄幼虫，观察其相互捕食结果和时间。七星瓢虫被寄生后的时间长短以及饥饿程度均不影响其与健康寄主之间的互相残杀效应；对捕食发生的潜伏期分析结果也未发现寄生后的时间长短以及饥饿程度可影响被寄生与健康寄主幼虫间的互相残杀效应。但啮小蜂寄生可影响七星瓢虫幼虫与集团内异色瓢虫之间的捕食效应，3龄七星瓢虫幼虫被异色瓢虫幼虫捕食的比例最高（21%），而1龄（9%）和健康幼虫（10%）被其捕食的比例较低；此外，被寄生的1、3龄和健康七星瓢虫幼虫面对异色瓢虫时的掉落比例分别为50%、43%和47%，说明掉落是七星瓢虫幼虫应对异色瓢虫捕食的主要防卫行为。研究结果说明，寄生不影响七星瓢虫幼虫在自相残杀中的地位，但刚被寄生的七星瓢虫幼虫更容易被集团内异色瓢虫所捕食。

While parasitoids of phytophagous insect pests have received considerable attention, those of predatory insects have attracted scant attention in their biology, behavior, and ecology. In this thesis study, a field investigation was firstly carried out to uncover parasitoid natural enemies attacking two dominant ladybirds Coccinella septempunctata and Harmonia axyridis. Among the parasitoids attacking the seven-spotted ladybird (C. septempunctata, C7) larvae, were collected two gregarious parasitoids (Hymenoptera: Eulophidae), Oomyzus scaposus and its closely related conspecific, not yet named scientifically and temporarily named as O. flavitibialis. These two parasitoids were compared in morphology, barcode of COI, and parasitism performances; hybridization trials between were made. Following studies focused on progeny allocation of these two parasitoids in response to the host already parasitized by each other, with host and wasp body sizes as covariates. The final study examined the performance of parasitized C7 larvae in cannibalism and intra-guild predation by H. axyridis. This thesis study provides new data for a comprehensive understanding of behavioral ecology of gregarious parasitioids attacking predatory ladybirds. What follows are main results and conclusions from this study. 1. Survey of parasitoid natural enemies of predatory ladybirds and comparison of two sibling eulophid parasitoids The survey in suburbs of Nanjing uncovered 8 parasitoid species from rearing C. septempunctata and 2 from H. axyridis. The most numerous species and highest parasitism rate were found in the habitat with least disturbance among three types of habitat varying at the level of anthropogenic disturbance. Pupae of H. axyridis were parasitized at the highest rate (5.31%) only by the Diperan phorid, Phalacrotophora sp., while C. septempunctata larvae were attacked by 26.1% and its pupae by 36.8%, to which Oomyzus parasitoids (> 15%) contributed most. Two species of Oomyzus parasitoids were found together attacking C7 larvae, O. scaposus and another one named temporarily as O. flavitibialis for the yellow hind tibia, which was differentiated from the former with black hind tibia.The differentiation between these two Oomyzus parasitoids was further supported by the results from hybridization trial, sequencing mitochondrial COI gene, and observation of parasitism performances. The scaposus had a longer egg-to-adult time (average 18.48 d) than the flavitibialis (16.46 d), a smaller brood (8.9) than the flavitibialis (11.62), and smaller offspring adults (female HTL: 0.47 mm, male HTL: 0.40 mm) than the flavitibialis (female HTL: 0.44 mm, male HTL: 0.36 mm). The two species were not different in offspring sex ratio (proportion males) (the scaposus, 0.18; the flavitibialis, 0.15). Host instar choice trials showed that O. scaposus did not prefer older hosts while O. flavitibialis preferred 3rd (90%) to 1st (10%) instar larvae. The residence time on host body of the 1st to 3rd instars was significantly longer for O. flavitibialis than for O. scaposus. The results suggest that O. scaposus and O. flavitibialis were the most important parasitic wasps of C7 larvae, and they were sister species. 2. Host discrimination and progeny allocation in multiparasitism The dual-choice trials showed that both naive and experienced O. scaposus females had no preference between healthy and heterospecifically parasitized C7 larvae. While naive O. flavitibialis females did not show the prefence the experienced preferred healthy to parasitized hosts. By the residence time on host body, O. scaposus, either naive or experienced, did not show any preference between the two hosts, but experienced O. flavitibialis stayed longer on healthy than parasitized host. A comparison between a single bout of parasitization and of stinging (the way of attack) showed different progeny allocation performances between the two parasitoids. For O. scaposus, brood size and sex ratio (proportion males) did not chage with the way of attack; for O. flavitibialis, brood size of a bout of parasitization was 1.75 times as large as a bout of stinging, though sex ratio same. In response to a parasitized host, 25% (n = 24) of O. flavitibialis females made the progeny allocationon the host attacked by a bout of parasitization and 71.4% (n = 24) on that by a bout of stinging, while 80.8% (n = 26) and 91.3% (n = 23) O. scaposus females made the allocation on the respective hosts. Females of these two parasitoid species did not change their progeny allocation in brood size and sex ratio in response to the host previously parasitized by each other. The results suggest that while O. scaposus may not be able to discriminate between healthy and heterospecifically parasitzed C7 larval hosts, O. flavitibialis may have such ability; these two parasitoids make progeny allocation irresponsive to the host previously parasitized by each other. 3. Body size dependant progeny allocation of O. scaposus We investigated the combined effect of host size across successive host larval stages and maternal wasp size on fitness-correlated performances of offspring parasitoids, using the larval-pupal gregarious parasitoid Oomyzus scaposus attacking C7. The results showed that the probability of parasitism success decreased with ladybird body weight at the time of parasitism when small sized wasps made the attack, but maintained a high level across the full range of host weights when large sized wasps made it. Offspring development time to adulthood decreased, while brood size increased, asymptotically with host body weight, but they did not vary with maternal wasp size. Sex ratio was female-biased and did not vary with ladybird body weight or maternal wasp size. Body size of F1 adult parasitoids did not vary with ladybird body weight or maternal wasp size. By extending the contact time between the host and the wasp, we can get samples with larger variation in brood size, which is much more close to the parasitic situation in the field, and evaluate the affects from another feature. The results showed that proportion males and egg-to-adult time were significantly affected by brood size. As brood size increased, the proportion males increased and the egg-to-adult time was shortened, while offspring size and emergence holes were not affected by brood size. Our findings suggest that small C7 ladybird larvae are preferred hosts for small O. scaposus females, while large sized ladybird larvae appeared to have little or no effect on parasitism success of large female parasitoids; proportion males increased with brood size. 4. Performances of parasitized C7 larvae in cannibalism and intra-guild predation This study aimed at examining the effect of parastized C7 larvae on intra- (cannibalism) and inter-specific (intraguild predation) competition. The results showed that the odds of winning of parasitized and healthy larvae did not differ under all treatments imposed. Cox proportional hazard model showed the predation risk of parasitized 4th instar larvae did not differ between being attacked at the 1st and 3rd instars. The median death time of them was 22 h and 22.5 h. Besides, the predation risk of 4th instar larval hosts separately parasitized at 1st between 12 h starvation and 24 h starvation was not significant as well. However, the larval median death time with 24 h starvation treatment (4 h) was shorter than that with 12 h starvation treatment (20 h). Then we recorded and examined the predation risk and behaviors of C7 larvae with different treatment in response to H. axyridis. The results showed that the probability of C7larvae being preyed was significantly influenced by the treatments. The probability of C7 larvae being preyed at the 3rd instar was highest (21%), but it was 9 % at the1st or 10 % in healthy larvae. The dropping probability was 50 % for the 1st instar, 43% for the 3rd and 47 % for healthy ones. The results from the present study suggest that parasitized C7 larvae were not at disadvantage over competitors in cannibalism, yet have a higher risk of predation by H. axyridis in the guild.