中文摘要：

实验室条件下以甜菜夜蛾各龄期幼虫为寄主,在大观察罩内的盆栽植物上模拟低龄（1～2龄）和高龄幼虫（3～5龄）在田间的分布特点接虫,在小观察罩内同质空间内混合各龄幼虫,分别观察斑痣悬茧蜂的寄主选择行为。研究结果表明,空间大小对斑痣悬茧蜂选择寄主龄期的行为具有很大影响。在大观察罩中,斑痣悬茧蜂对甜菜夜蛾低龄幼虫（1～2龄）的遭遇和放弃行为比例均大于高龄（3～5龄）幼虫,而在小观察罩内的表现则相反。虽然斑痣悬茧蜂的寄主处理时间随寄主龄期的增大而延长,但在大观察罩内斑痣悬茧蜂花费的寄主处理时间比在小观察罩内长。在小观察罩内,寄生蜂对低龄幼虫的再次攻击间隔时间（653.17s）长于高龄幼虫（171.32s）,但在大观察罩内则相反。在大观察罩内低龄幼虫的被寄生率（23.24%～38.54%）高于小观察罩内（7.88%～21.43%）,但是小观察罩内高龄幼虫（4龄）的被寄生率（34.65%）大于大观察罩（16.86%）。最后,就空间大小影响斑痣悬茧蜂寄主选择行为的机理进行了探讨。

英文摘要：

Host-instar selection behaviors of Meteorus pulchricornis in small and large arenas under lab conditions were observed using all larval instars of Spodoptera exigua as hosts.The host distribution on potted plants in the large arena was manipulated to simulate field spatial aggregation in L1-L2 and dispersed distributions in L3-L5.In the large arena,the parasitoid performed more encountering and rejecting acts toward young host larvae（L1-L2） than toward old host larvae（L3-L5）,but in the small cage the above pattern was reversed.Host-handling time was significantly longer in the large cage than in the small cage for each instar host,and increased linearly with increase in host instars both in the large and small cages.The parasitoids in the small cage resumed attacks on young larvae after 653.17 s and on old larvae after 171.32 s,whereas the reverse was observed in the large cage.The young larvae（L1-L2） were parasitized at higher rates in the large cage（23.24%-38.54%） than in the small cage（7.88% -21.43%）,but old larvae（L4） were parasitized more than in the small cage（34.65%） compared to the counterparts in the large cage（16.86%）.Our studies suggest that arena space can have major impacts on their host selection behaviors.Finally,mechanisms of differences in host selection behaviors in M.pulchricornis in different-sized spaces were discussed.