Composition and Diversity of Gut Bacterial Community in Different Life Stages of Osmia excavata Alfken (Hymenoptera: Megachilidae)

<i>Osmia excavata</i> is an excellent pollinator in nature and plays a vital role in the conservation of agro-ecosystems and food security. Given the important role of the gut bacterial community in host health and regulation of host growth and development, using 16S rRNA gene sequencing data, the present study explored the composition of the gut bacterial community and its diversity at different life stages (eggs, young larvae, old larvae, young pupae, old pupae, and 1-day-old adults in cocoons) of the solitary bee <i>Osmia excavata</i>. The results showed that the core phyla in the gut of <i>O. excavata</i> at different life stages were Proteobacteria, Firmicutes, Bacteroidota, and Actinobacteriota, and the core genera were <i>Sodalis</i>, <i>Tyzzerella</i>, and <i>Ralstonia</i>. The highest intestinal bacterial diversity was found in the Egg period, and the lowest bacterial alpha diversity was found in the 1-day-old Adult period; the bacterial diversity of <i>O. excavata</i> showed a process of decreasing, as it was growing from the Egg period to the 1-day-old Adult period. Our study found that <i>O. excavata</i> undergoes a significant change in the structure of the gut flora when it grows from the young pupae to old pupae stage, a period of growth that coincides with the process of cocooning and isolation from the external environment after food depletion. This suggests that food and environmental factors are key contributors to the structure of the bacterial community in the gut of solitary bees.