Mating Behaviour Of Galerucella Birmanica Jacoby

Galerucella birmanica Jacoby(Coleoptera: Chrysomelidae) is a serious pest in south China where water caltrop, Trapa bispinosa Roxb, is commonly planted as an aquatic vegetable. The adults and larvae of G. birmanica feed on the leaves of water caltrop and seed yield could be significantly damaged. Knowledge about the impact of multiple mating or exposure to males on female reproduction is important for predicting the population dynamics of G. birmanica and for the development of control methods such as sterile insect technique. This paper studied the effect of multiple mating on female fitness and investigated female mate choice. Also we study the male competitive plasticity. Results are summarized as below:(1) Under restricted exposure conditions, where females were exposed to males only when mating, multiple mating significantly reduced female longevity, but promoted female daily and lifetime reproductive output(LRO) significantly. The average LRO increased from 404.31 to 674.62 eggs per female when mating number increased from 1 to 5. Multiple mating also boosted the hatch rate of eggs, especially those produced in the late oviposition stage. Under continuous exposure conditions, females housed with 4 males died significantly younger than females housed with 2 or 1 male, and they also died younger than females subjected multiple mating but with restricted exposure to males. The LRO decreased significantly with the increasing of number of males that the female was exposed to, and was significant lower for females continuously exposed to males than those with restricted exposed to males. Continuous exposure to males had no significant effect on egg hatch rate throughout the ovipositing period. These results demonstrated that multiple mating is important for female G. birmanica to achieve optimal reproductive output, but male harassment on females caused by exposure to males outweighs this benefit.(2) When females mated with males of different body size, female life time eggs and daily eggs, had no significant difference between treatments. When females mated with males of different age, female life time eggs, daily eggs and hatching rate had no significant difference between treatments. When females mated males with different sexual experience, female life time eggs, daily eggs and hatching rate had no significant difference, too. These results indicated females did not show preference for male size, age, and sexual experience.(3) Multiple mating is common in insects, which leads to males competing for mates and sperms competing for fertilizing the eggs. Males predict the intension of male competition according to the population density at the stage of larva and adult, and then they adjust strategy to maximize their reproductive output. We tested the plasticity of male competition under different population density. The results indicated that the duration of male response to female increased with the number of male rivals; but the density in stage of larva had no significant effect on duration of male response to female. Mating duration was not affected by larva density or the number of male rivals. The number of sperms not associated significantly with larva density or the number of male rivals, but seminal fluid proteins content was affected by larva density or the number of male rivals. The more the male rivals, or the higher the larva density, the more seminal fluid proteins content the males had. Therefore, males adjusted behavior and physiology according to the living environment of larva and adult male in order to achieve reproductive benefit maximization.