[Objectives]  To investigate the morphological characteristics, developmental duration, generation time, fecundity, and behavioral features, of immature stages and adults of Danaus genutia (Cramer), collected from Yuanjiang county, Yunnan province. Some potential host plants reported in the literature were also investigated. [Methods]  Life-cycle stages and duration of each stage were observed by rearing eggs, larvae and pupae individually in a climatic chamber. An experimental green-house population was founded to collect life history data. The behavior of larvae and adults were observed in both the green house and the field. Simultaneous choice, and sequential no-choice, experiments to determine adult oviposition and larval food preferences were conducted to identify likely host plants. [Results]  At 25℃, the period from egg to adult eclosion was 22-27 days, whereas that from egg to oviposition was 35-40 days. The sex ratio of the experimental population was 1∶1.26 and the average fecundity was 64.84 eggs per female. Two plant species in the genus Cynanchum (Asclepiadaceae); Cynanchum otophyllum and C. giraldii, were confirmed to be host plants of local Danaus genutia populations. [Conclusion]  There are obvious morphological differences among the larvae of different geographic populations of D. genutia, polymorphism in larval color and pattern, and local host-plant specificity. Two species of 

Cynanchum were confirmed to be host plants of the local D. genutia population but there was no evidence that the other nine previously reported host plants are, in fact, host plants of this species.