This paper presents a study on the biology of Byasa impediens, and includes life table data and the analysis of the habitat requirements and key factors causing threats to this species. It aims at the detection of specific protection methods, in order to guarantee the long-term survival of Byasa impediens in Baishuijiang Reserve.
Byasa impediens: Bivoltine in Baishuijiang reserve. Overwintering: pupae on shrubs or tree branches. Eclosion of first generation starts in MidApril. The adults of first generation will emerge with a great quantity in Mid-late May, and the second one will be on the wing from late June to MidJuly. The two generations overlap. The male adults emerge 710 days earlier than females. Perching along small rivers and gullies and flower visits determine their flight behavior. They are strong fliers. On the contrary, the flight ability of females is weak, thus they just visit flowers, mate and lay eggs near the natal area. The ratio of female to male is 1∶4.1. The male can live for a maximum of 26 days with an average of 6.9 days, while females have a maximum of 21 days with an average of 7.6 days. The fertilized eggs per female are 31.5 on average. The adults prefer the following nectar plants: Albizzia julibrissin, Bauhinia glauca, Clerodendrum bungei, and Sambucus chinensis.
Habitats: the plant Aristolochia heterophylla is distributed from 900m to 1680m of elevation, and the most suitable range is from 1200m to 1500m. Host plants grow mainly along paths and along borders of forests in which the canopy is rather open and which have shrubby undergrowth. The plant can be hardly found when canopy density of forest is over 0.8. The most suitable elevational range of larvae is from 1200m to 1500m. The ideal habitat of host plants also seems to be the ideal habitat of Byasa impediens.
Key factors that negatively affect the population of Byasa impediens are habitat loss and deterioration. The loss and deterioration of habitats result in lower numbers of host plants and a more restricted distribution of potential habitats. The habitat will be influenced easily by anthropogenic activity, such as herding, cultivating and using pesticides, which will especially influence the growth of host plants Aristolochia heterophylla and larvae of butterflies. Abnormal climatic conditions and natural enemies are key factors for the population density. Hot and dry weather in summer and too much rain in autumn reduce the survival rate of eggs and larvae very much. Ichneumon parasitoids reduce the survival rate of over-wintering pupae. The natural enemies of larvae include spiders, earwigs, wasps, bugs and ichneumon parasitoids. Further natural enemies of pupae and adults are birds.
The most important conservation measures are preservation and reconstruction of the natural habitat, which includes recreational forestry, the enhancement of management, enforcing existing laws, and developing Eco-tourism. Creating a core-patch at a central area near to all patches is also an important measure. In the most ideal habitat, appropriate shrub cutting can increase the host plants growth and then promote the population of Byasa impediens.