Nesting characteristics of Megachile rixator (Hymenoptera: Megachilidae)

Author of the article:GUO Peng-Fei, GUO Shi-Kun, WANG Ming-Qiang, LI Yi, CHEN Jing-Ting, YANG Juan-Juan, LUO A-Rong, ZHU C

Author's Workplace：Key Laboratory of Zoological Systematics and Evolution, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China

Key Words：leaf-cutter bee; solitary bee; subtropical forest; trap-nest; sex ratio

Abstract：[Objectives]  To investigate the nesting biology of Megachile rixator in order to provide a theoretical basis for the protection, artificial management and domestication of this pollinating bee species. [Methods]  A total of 88 sample plots were established at the BEF-China experimental site in Xingangshan town, Dexing city, Jiangxi province, China between August 2015 and July 2020. Standardized trap-nests were used to collect M. rixator whose biological characteristics were then recorded and analyzed. [Results]  A total of 866 nests were recorded, 347 of which were successful with an overall mortality rate of 60%. The ratio of female to male offspring was 0.57. Females built nests using plant leaves from May to November, building an average of (3.75 ± 2.24) nests each time. The average diameter of nests was (10.00 ± 2.37) mm, and nests tended to be within the range of 11-13 mm. Diapause occurred after September and individuals overwintered in the pre-pupal stage. The sex ratio of offspring peaked in May after which it decreased each month until increasing again in November. The sex ratio of offspring was lowest in nests with a diameter of 5-7 mm, was higher in nests of moderate diameter, and lower in nests with a diameter of 13-15 mm. [Conclusion]  M. rixator is a typical solitary, leafcutter bee species that uses plant leaves to build nests. It is, however, polymorphic. Each nest produces multiple offspring and has a high mortality rate. Nesting takes place continuously from late spring to late fall each year. The sex ratio of offspring tends to be male biased. Female M. rixator can be collected from September to November using trap nests with a thicker inner diameter.