Foraging and main pollinators of Jatropha curcas in dry-hot valley.
Luo ChangWei, Li Kun, Chen XiaoMing, Chen You, Sun YongYu
Author Affiliation: The Research Institute of Insect Resources, Chinese Academy of Forestry, Kunming 650224, China.
Chinese Bulletin of Entomology 45 : 121-127
Abstract : To get a raise in its fruit set ratio, improve its yield, and provide scientific basis for large-scale planting, the foraging insects and main pollinating insects in the half-cultivated population of Jatropha curcas, an important biodiesel-producing crop, in Yuanjiang County, Yunnan Province, China, were investigated in 2006. J. curcas was planted along a country road as a hedge on a flatland in Yuanjiang dry-hot valley, near some economical crops including Mangifera indica, Musa acuminata, Jasminum sambac, Saccharum sinense, which provided good habitat for the insects. J. curcas produced flowers in racemose inflorescences, with dichasial cyme pattern. Its male and female flowers were produced in the same inflorescence. Normally, the inflorescences produced 184±189.02 (88-238) male flowers with bright yellow stamens. Everyday, 9.94±29.58 (0.21-21.57) of them open on the crown of the tree, making a great floral display. Both male and female flowers produced flower odour and nectar. Its salver-shaped flower base promised many kinds of insect-harvestable honey. Thirty-five foraging insect species, belonging to 5 orders and 20 families were observed, with half of them belonging to Hymenoptera, and the others belonging to Diptera, Lepidoptera, Hemiptera, and Coleoptera. By comparing the number and the pollination effectiveness of the foragers (including their foraging behaviour, foraging frequency, and daily activity rhythm), the main pollination insects were identified as: Chrysomya megacephala, Apis cerana and Catopsilia pomona f. crocale. These species had different foraging behaviour. The former two were smaller in body size than the honey bee, making it easy for them to transfer pollen from the stamens to the stigmas. However, honey bees were greater in number, thus compensating for their pollen-carrying ineffectiveness. The daily activity rhythm differed among the three pollinators, but was identical between male and female butterflies. Furthermore, the composition of foraging insects was influenced by the weather conditions, floral display and habitat conditions. It is concluded that the main pollinators showed differences with changed time and space.