Many parasitoids discriminate previously parasitised hosts from unparasitised ones to avoid mortality of offspring. Parasitoids that parasitise aggressive hosts such as lepidopteran larvae are known to attack hosts very quickly to avoid being attacked. However, little is known about host discrimination of such quick attacking parasitoids. We investigated host discrimination of Microplitis demolitor (Wilkinson) (Hymenoptera: Braconidae) a quick attacking parasitoid of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae). Results showed that ratios of female wasps that rejected the hosts after antennal examination did not differ between parasitised and unparasitised hosts, indicating that M. demolitor did not discriminate hosts by antennal examination. However, 95% of females that inserted ovipositor into unparasitised hosts actually laid eggs, whereas it was only 31% for parasitised hosts, indicating that females discriminated hosts by oviposition insertion. Analyzing video recordings revealed that the ovipositor exploration of the host took 0.3 s. Female wasps that had experienced high-host density of unparasitised hosts readily rejected parasitised hosts, while wasps with experience of low host availability of parasitised hosts tended to accept parasitised hosts. This suggests that host discrimination behaviour of M. demolitor is affected by previous experience of different host availability and host quality.

为了避免后代的死亡，许多寄生虫将先前寄生的寄主与未寄生的寄主区分开来。寄生于诸如鳞翅目幼虫等侵袭性宿主的寄生虫会非常迅速地攻击宿主以避免被攻击。但是，对于这种快速发作的寄生虫的宿主鉴别知之甚少。我们调查了棉铃虫（Hulbner）（鳞翅目：夜蛾科）的一种快速发作的寄生性寄生虫（Micropilitis demolitor，Wilkinson）（膜翅目：Braconidae）的宿主歧视。结果显示，在寄生和未寄生的寄主中，接受触角检查后拒绝寄主的雌性黄蜂的比率没有差异，这表明M. delitor没有通过触角检查区分宿主。然而，将产卵器插入非寄生虫宿主的雌性中有95％实际上产卵，而寄生虫宿主只有31％产卵，这表明雌性通过产卵插入来区分宿主。分析视频记录显示，对宿主的产卵器探索耗时0.3 s。经历过非寄生虫寄主高寄主密度的雌性黄蜂很容易拒绝寄生虫寄主，而寄生虫寄主的宿主利用率低的黄蜂倾向于接受寄生寄主。这表明除臭支原体的宿主歧视行为受先前不同宿主可用性和宿主质量的经验影响。