1. College of Grassland Science and Technology, China Agricultural University, Beijing 100193, China
2. Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, China
3. National Animal Husbandry Station, Ministry of Agriculture, Beijing 100125, China
4. The Affiliated High School of Peking University, Beijing 100190, China
5. Department of Entomology, Pennsylvania State University, University Park, PA 16802, U.S.A.