The effects of oviposition experience and host deprivation on host preference in Callosobruchus chinensis (L.)

The main goal of this study is to understand the changes of host preference based on the previous experience. Because Callosobruchus chinensis is an endophagous insect, and adults do not feed, the nutrition resources of this species is totally determined by the choice of the female. Therefore, the oviposition of females affects survival of offsprings. The host plant,of Callosobruchus chinensis, is the plant of Legurninosae. Females lay eggs on the seed. In the no-choice tests, females accept azuki bean or mung bean as host without significant difference in preference. However, females prefer to oviposit on azuki bean when it can choose between the two hosts. There are many factorses such as oviposition experience to affect oviposition. The study is composed of four portions to explore female ovipositional preference. Firstly, the previous ovipositional experience did not increase the host preference on mung bean. Female showed significant host preference on azuki bean even they had oviposited on mung bean. However, the ovipositional experience on azuki bean did not increase the host preference on it. Furthermore, we tested the effect of different ovipositional experience on host acceptance. The result showed that females shortened the acceptance time on azuki bean when they had ovipositional experience on mung bean. On the contrary, females needs more time to accept mung beans for oviposition when the situation was reversed. Based on these results, we confirmed the learning ability of Callosobruchus chinensis on host acceptance. Secondly, we investigated the effects of host deprivation on host preference. It was clear that host deprivation did cause the pressure of egg load. Although females speeded up to oviposit on host in order to release the pressure, they still preferred to lay eggs on azuki beans. The females did not increase oviposition on mung bean even with 24 hours of host deprivation. Regardless of host resources, females preferred to oviposit
on azuki beans. Females would lay the first egg on azuki bean right after a period of host deprivation. The result implied that the innate host preference could not be changed by host deprivation. Thirdly, we explored the effects of interference and competition experience on host preference. The results showed that females did not change ovipositional preference with the interference experience of being together with other females without host resource. However, females with competitive experience did not increase the host preference on mung bean when they were offered with azuki beans and mung beans. Fourthly, the main issue is the effect of intraspecific competition during oviposition on host preference. We found that females did slow down to oviposit while the numbers of females in competition did increase. The competition did not increase its preference on mung bean regardless the quantity of host resource. Therefore, we could conclude that the most prominent factor to determine the host preference was built in the host species.