白蜡吉丁柄腹茧蜂的寄生和繁殖生物学

白蜡吉丁柄腹茧蜂Spathius agrili Yang是我国天津地区寄生白蜡窄吉丁幼虫的一种重要天敌。本研究通过林间调查并结合室内观察，测定了该寄生蜂在不同营养条件下的存活时间和不同时期的产卵量，调查了不同寄主大小对寄生蜂后代生长发育的影响，以及寄生蜂对不同深度树皮下的寄主利用情况。结果表明：不同营养条件下白蜡吉丁柄腹茧蜂的存活时间差异很大，补充20％蜂蜜水的成蜂存活时间明显延长，最长可达3个月。相同条件下雌蜂的存活时间比雄蜂略长。在补充营养的条件下，茧蜂的产卵时间最长可达8周，产卵的高蜂在羽化后第2周前后，平均每雌每周产卵量在整个产卵期内基本保持在8～12粒上下，没有大的波动。茧蜂低龄幼虫也可能分泌毒素主动攻击寄主，提高了寄生蜂后代的生存能力。寄主个体大，营养量也大，寄生其上的茧蜂幼虫成功完成发育的数量随之增加，表明寄主营养资源的多少直接影响到寄生蜂后代的生长发育和存活。白蜡吉丁柄腹茧蜂对1～6.5 mm树皮深度范围内的适龄寄主幼虫均能够寄生利用，约92％的被寄生白蜡窄吉丁幼虫个体分布于1～4 mm深度的树皮下，在3 mm厚的树皮下分布的数量最多。茧蜂数量与树皮深度大致上呈抛物线关系，理论上在树皮深度为3.97 mm处茧蜂分布数量最多。

Parasitism and reproductive biology of Spathius agriliYang (Hymenoptera: Braconidae)

Spathius agrili Yang(Hymenoptera: Braconidae) is an important natural enemy parasitizing larvae of the emerald ash borer(EAB),Agrilus planipennis Fairmaire(=A.marcopoli Obenberger)(Coleoptera: Buprestidae),in Tianjin,China.The survival time of S.agrili under different nutrimental conditions,egg productions of the parasitic wasp at different periods,influence of host size on the development of wasp offspring,and utilization of host beneath the bark of different thickness,were investigated in fields, combining with observations in the laboratory.The results showed that the survival days of the parasitoid differ significantly under different nutritional conditions.Wasps can live pronouncedly longer after feeding 20% honey dilution with the maximal survival time of 3 months,and under the same conditions females usually can survive a little longer than males.When supplied with nutrition,the maximum period for oviposition of the braconid is up to 8 weeks with the peak around the 2nd week.During the whole oviposition period,the mean egg production of 8-12 eggs per female per week is almost constantly maintained without high fluctuation.The newly hatched larvae of S.agrili may produce venoms and attack host initiatively,so help to improve the survival opportunities of parasitoid progeny.The number of successfully developed parasitoid offspring from host enhances with the increase of host larval weight,which indicates that the host nutrition capacity affects the development and survival of wasp progeny.S.agrili can utilize those hosts at right ages beneath the bark of 1-6.5 mm in thickness.Approximately 92% EAB larvae parasitized by Spathius are distributed at 1-4 mm thickness of the bark with the peak at 3 mm.Relationship between the number of wasps and bark thickness can be simulated with a quadratic parabola roughly,and the theoretical maximum number of the parasitoid would be expected at 3.97 mm thickness of the bark.