1. a Nagahama Institute of Bio-Science and Technology , 1266 Tamura-cho, Nagahama, Shiga 526-0829, Japan
2. b Department of Mathematical and Life Sciences , Graduate School of Science, Hiroshima University , 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8526, Japan
3. c Natural Science Center for Basic Research and Development , Hiroshima University , 1-4-2 Kagamiyama, Higashi-Hiroshima 739-8526, Japan
4. d Yamada Apiculture Center, Inc. , 194 Ichiba, Kagamino-cho, Tomata-gun, Okayama 708-0393, Japan