Tuesday, December 12, 2006

Exploring the effect of adult egg-laying experience on host acceptance of seed beetle, Callosobruchus maculatus (F.)(Coleoptera: Bruchidae)

Rou-Ling Yang, f87632005@ntu.edu.tw, Shiau-Min Dai, and Shwu-Bin Horng, sbhorng@ntu.edu.tw. National Taiwan University, Department of Entomology, #1, Sec. 4, Roosevelt Road, Taipei, Taiwan

Previous studies showed that recent egg-laying experience may play little or no role in seed beetleís host species discrimination, but they always could not rule out the effect of individualís physiological state (i.e., egg-load). Therefore, (1) minimizing individual differences in egg-load by shortening the experimental protocol, and (2) offering different host species sequentially every 30 minutes, were used in this study to test the effect and the duration of egg-laying experience on host acceptance of the seed beetle, Callosobruchus maculatus. It was found that adult egg-laying experience did affected its later host acceptance. The number of eggs laid on host drastically decreased when adults were transferred from adzuki beans to mung beans. As the adults were transferred from mung beans to adzuki beans, the number of eggs laid significantly increased. In addition, it was first found that the effect of adzuki-laying experience could inhibit later oviposition on mung beans for 2.5 h at least. Removing the seed coat could change the beetlesí acceptance on adzuki beans but not on mung beans. Thus, there might be no inhibition substance on mung beansí coat, but might be a character for host recognition on seed coat of adzuki beans. It was proposed that this character played an important role in host-rank determination and might be a cue for learning. The lost of such character on mung beans is an interesting issue in exploring insect-plant interaction.

Species 1: Coleoptera Bruchidae Callosobruchus maculatus (seed beetle)