Host Selection Behaviour Of Microplitis Pallidipes Szépligeti And Its Mechanism

In this study, we investigated the selection behavior of Microplitis pallidipes Szépligeti on Spodoptera exigua(Hübner) and Spodoptera litura (Fabricius), and distinguish between virus infected and noninfected S. litura larvae. The effects on learning experience by parasitoid on its host selection. And Preliminary Study on the identify mechanism of virus infected and noninfected S. litura larvae. The results are as follows:1 The selection behavior of M. pallidipes to S. exigua and S. lituraThe experience of prepupal stage would have some influence on searching and distinguishing between two kinds of vegetable armyworms by M. pallidipes. The parasitoid preferred to attack reproductive host at the first time. The time of attacks was also shorter. Parasitoids spend more time on attacking S. exigua. This was not influenced by the experience of prepupal stage. The searching ability would be increased for adults when they have learning behavior. The parasitoids choose the one which he has learned. The searching time and the time of attacks would be less when he has learned it. Rates of Parasitism would be higher than control.2 The selection behavior of M. pallidipes on virus infected and noninfected S. litura larvaeThe M. pallidipes could distinguish between the healthy and virus infected larvae. When the virus concentration was 1.68×108 PIBs/ml, parasitoids would be more like to choose the healthy hosts in the third day after larvae fed with the virus. This result was the same as the experiment of field caging. Parasitoid would be more like to choose the healthy hosts in the fourth day after larvae fed with the virus when the virus concentration was 1.68×107 PIBs/ml. When the virus concentration was 3.36×106 PIBs/ml, the choice of wasps has the tendency, but the difference was not significant. The rates of parasitism change along with the change of attack times. The decreasing rates of parasitism might be caused by the development of larvae. The M. pallidipes preferred the virus infected larvae in the first day (virus concentration was 1.68×107 PIBs/ml), 1th-2nd (virus concentration was 3.36×106 PIBs/ml) day after virus inoculation. When virus concentration was 1.68×108 PIBs/ml, we could not see the difference. Another experiment shows us that experience of larvae for the wasps could help them to distinguish healthy and virus infected larvae. This results showed that M. pallidipes spend less time to find the virus infected when it born of the same one. The time of attacks was less too. They first like to attack treatment of virus. From this test, we could know that the wasps could remember something when they were young. But this remembrance was not influence the final choice. It just effect on the first searching and identification. After the parasitoids attacked the host many times, they would choose the healthy hosts and avoid the infected ones finally. The learning behavior of the adult wasps played an important role in their choosing behavior. It would choose the healthy one if it had pocked the body of virus treatment. Compare with the virus treatment, the parasitoid spended less time on searching the non-infected hosts, more times to attack it, rates of parasitism was significant increased. But the times of attack by the wasps for the healthy host was always more than those for virus infected larvae.3 The tendency behavior of M. pallidipes for the larvae and the damaged plantsThe tendency behavior of M. pallidipes could not distinguish the infected and non-infected larvae in 1st to 4th day after the larvae fed with virus. In the 5th day, the parasitoid preferred to choose healthy one. The wasps would choose the health host after 4 days post virus inoculation when the smells include larvae and damaged plants. The parasitoid could not find the difference between healthy and infected host according the shit of the larvae. The wasp was not slide over the solution of virus.4 The influence on melanin and the PPO activity for the SINPV infected larvaeAfter the S. litura larvae were fed with virus, the virus increased in the larvae, while the melanin decreased. 4 days later. The contents of melanin were significant different with those in healthy larvae. In this research, comparing the SINPV–infect larvae and the non–infected larvae. We saw that the PPO activity of was rising continually after virus inoculation. 3 days later, The PPO started falling down. Finally, the PPO activity was lower than the level in the healthy host.