The nesting, oviposition and life history, of Chalybion hainanense

Author of the article:ZHANG Chu-Ge1, 2** OUYANG Fang2 WANG Ming-Yi2, 3 ZHOU Hao2, 4 CHEN Li-Lin5*** XIAO Zhi-Shu2, 4

Author's Workplace：1. Anxi College of Tea Science, Fujian Agriculture and Forestry University, Quanzhou 362406, China; 2. State Key Laboratory of Integrated Management of Pest Insects and Rodents in Agriculture, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China; 3. College of Life Sciences, Hebei University, Baoding 071002, China; 4. College of Biological Sciences, University of Chinese Academy of Sciences, Beijing 100049, China; 5. State Key Laboratory of Agricultural and Forestry Biosecurity, College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou 350002, China

Key Words：Chalybion hainanense; artificial nest tube; incubation chamber; life history; individual size; reproductive strategy

Abstract：[Aim]  To describe the nesting, oviposition and life history, of Chalybion hainanense, and thereby clarify the reproductive strategy of this species. [Methods]  Eighty artificial trap-nests were deployed within the forest dynamic plot in Chebaling National Nature Reserve in Guangdong Province. Trap-nests used by solitary bees and wasps were collected, and their progress monitored by regular indoor observations. In addition, the nesting structure and adult body size of C. hainanense were measured. [Results]  In 2019, a total of eight trap-nest collections were conducted, yielding 433 C. hainanense nests and 450 brood cells. On average, each trap-nest contained (1.04 ± 0.19) brood cells, with 96.07% containing a single egg. The average length of brood cells was (105.12 ± 49.62) mm, the average diameter was (9.64 ± 1.27) mm and the average volume was (7 623.97 ± 3 991.80) mm³. The offspring sex ratio was female biased (♀∶♂ = 1.23∶1), and the diameter of nests and the volume of female brood cells were significantly larger than those of males, although there was no significant difference in brood cell length between the sexes. C. hainanense has two generations a year in Guangdong, the second of which overwinters in pre-pupal form and starts to emerge in mid-May the following year. The egg stage lasts 2 to 3 days, after which the larvae feed on spiders, taking 6 to 7 days to pupate. Larvae pupate for 38 to 44 days before eclosion, whereas the overwintering generation undergoes a diapause period of 220 to 290 days. Female body length and head width are significantly greater than those of males. Among females, head width shows a significant positive correlation with tube diameter, and individuals of the second generation are significantly larger than those of the first generation. [Conclusion]  The nesting and oviposition behavior of Chalybion hainanense, together with other life history traits, reflect its adaptability and complex reproductive strategy. These findings provide critical insights into the ecological significance of this species and inform conservation strategies.