多胚发育寄生蜂腰带长体茧蜂在寄主亚洲玉米螟幼虫体内的发育

多胚发育的幼虫内寄生蜂腰带长体茧蜂Macrocentrus cingulum的卵、胚胎和幼虫在寄主亚洲玉米螟Ostrinia furnacalis幼虫血腔内发育，通常1枚卵可以分裂增殖为数百只胚胎。本文通过定时解剖寄生的寄主幼虫，初步了解了腰带长体茧蜂多胚的形成过程及其在寄主体内的发育情况。结果表明：以4龄末期亚洲玉米螟幼虫为寄主时，寄生蜂卵产入寄主体内10 min左右开始卵裂，1天左右，初级胚胎从卵壳中被释放出来。之后胚胎在胚外膜内持续分裂产生大量二级胚胎形成桑葚胚。寄生后3天左右，二级胚胎从胚外膜中被释放出来，进入胚胎发育阶段。寄生后6天左右，胚胎进入胚带形成阶段。寄生后8天左右，胚带伸长，头尾形成。寄生后9天左右，身体分节完成，部分幼虫孵化，蜕去胚外膜。寄生后13天左右，蜂幼虫从寄主体内啮出。胚胎在发育初期体积变化不大，但从胚带形成开始，体积则迅速增大。腰带长体茧蜂与另一多胚发育寄生蜂佛州点缘跳小蜂Copidosoma floridanum在胚胎发育进程上明显不同，体现了它们对各自寄主的适应。

Embryonic development of polyembryonic Macrocentrus cingulum (Hymenoptera: Braconidae) in the hemocoei of host Ostrinia furnacalis (Lepidoptera: Pyralidae) larva

Eggs,embryos and larvae of wasp Macrocentrus cingulum,a species of polyembryonic endoparasitoid develop in the hemocoel of host,within which usually one egg of the wasp may cleave and proliferate into several hundred embryos.In this study,the course of the embryo formation and the development of the wasp in host body were observed through dissecting parasitized host larvae at regular time interval.When the late 4th instar larvae of Ostrinia furnacalis were used as host,wasp eggs began to cleave within eggshell in ten minutes after oviposition,and preliminary embryonic cells raptured out of the chorion in about 1 day after oviposition.Then the preliminary embryos cleaved into a large number of secondary embryonic cells within extroembryonic membrane to form morulae,and the secondary embryonic cells were released and initiated morphogenesis 3 days after oviposition.Embryos entered the formation of germband 6 days after oviposition,and then germband extended and head and tail were formed within two days.Embryos were fully segmented,and then the first instar larvae hatched out of the extraembryonic membranes about 9 days after oviposition.Mature larvae gnawed out of body wall of the host 13 days after oviposition.At early developmental stage,size of the embryos increased slowly,but rapidly after the formation of germband.Differences existed between M.cingulum and another polyembryonic endoparasitoid Copidosoma floridanum in the course of development in host hemocoel,and this may be due to their adaptation to specific hosts.