Studies On The Sexual Selection And Copulation Of Octodonta Nipae (Maulik)(Coleptera: Chrysomelidae)

Octodonta nipae (Maulik) is one of the most important pests of palmae plants,which has a strong adaptive and reproductive capacity. This study systematicallyexamined reproductive behavior of O. nipae by three aspects, the mating rhythm,sexual selection and mating behavior. The main results were summarized as follows.1. After emergence, the beetle had to experience a period of feeding nutrition, thenthey could mate with each other. The results showed that the precopulation duration ofmale (15.17±1.59d) was longer than that of female (6.67±1.95d). After copulation, thefemales not only need to feed, but also need to reach certain ages to lay eggs,generally for19.76±1.74d after emergence. Copulation behavior could be observed allday long, but maintained a higher mating rate from9:00to20:00. At the age of28d to32d, the beetle was more active; the adults copulated as much as5.45±0.85times aday.2. The beetles had a female-biase sexual size dimorphism. The males prefered tomate with the females whose body weights were heavier, the females prefered tochoose the males with small body size. Females and males prefered to choose theadults with sexual maturity as spouse. At the same sexual mating level, adults had noselection on the age of spouse. Virgin females and mated males had no selection onspouses’ mating experience, virgin males prefered to mate with mated males, matedfemales chose to copulate with mated males.3. The beetle completed amating processes including five steps, approaching,mounting, joining, locking and leaving. The result showed that, affected by manyfactors, the beetle’s mating durations were different. There were no significantrelationships between mating duration and body weight or female’s density orexperience of males. But mating duration of the beetle was affected by adults’ age,females’ mating experience and male’s density. Within the range of certain age,mating duration was extending with the increasing of age of adults. After emergence,the beetle didn’t mate with each other; however, the mating duration of the beetlemight be significantly decreased. Mating duration reached a maximum with the sex ratio of1♀:2♂, while decreased with the number of male. It was found that beetle’sformer mating affected the mating duration of remating.