野外环境中斑痣悬茧蜂的产卵选择行为

为探究寄生蜂寄生率与寄主密度的依赖方式及其与寄生蜂搜寻选择寄主行为的关联,以斜纹夜蛾幼虫为寄主在大豆田进行了斑痣悬茧蜂野外释放-回收试验。结果表明:寄生率与寄主密度的依赖关系不是固定不变的,而是存在一个密度阈值(≈8头.株-1),在低于此阈值的密度范围内,寄生率随密度增大而明显降低;高于此密度阈值时,寄生率保持约50%的水平。采用跨栏模型分析寄主体质量对寄生概率和过寄生程度的影响表明,寄生率随寄主体型(用体质量表示)增大而降低,但寄主体型大小对过寄生程度(用寄主体内的卵数表示)没有显著影响,过寄生率为23.9%。根据研究结果推测,斑痣悬茧蜂在大豆植株上对寄主幼虫的搜寻采取随机方式,在寄生健康寄主时依据寄主体型大小评价寄主,但在过寄生时并不依据寄主体型大小。

Oviposition selection behavior of Meteorus pulchricornis ( Hymenoptera: Braconidae) in the field

To understand the association between host density and parasitoid host-foraging behavior,a release-recapture trial was conducted in the soybean field by using Spodoptera litura larvae and its solitary parasitoid Meteorus pulchricornis(Westmael).The results showed that the dependence of parasitism on host density was not constant,but hinged upon the host density threshold(≈8 larvae/plant),below which parasitism rate decreased with host density while beyond which it remained at about 50%.The analysis using the hurdle model indicated that the probability of single parasitism declined with host body size(body weight)but the extent of superparasitism,as measured by the number of eggs in a host,did not varied with host body size;superparasitism rate was as high as 23.9%.The study suggested that M.pulchricornis might randomly forage on plants,making use of host body size as the cue at single parasitism but not at superparasitism.