Gut microbiome establishment during development is important for healthy host–microbiome symbiosis. Honeybees and bumblebees both have simple and host-specific gut microbiomes, but their colony cycles are very different. Honeybees and bumblebees both have simple and host-specific gut microbiomes, but their colony cycles are very different. While honeybee colonies persist for years, bumblebee colonies are newly established each year by solitary queens and unlike those in honeybee colonies, the mechanisms of microbiome development in bumblebee colonies remain unclear. To learn more, researchers recently used metagenomics to track microbiome changes in laboratory-raised bumblebees and their colonies over time. Some core microbes persisted throughout development and the gut microbiomes of newly emerged worker bees always resembled that of the queen, indicating vertical transmission from mother to offspring. As the colony grew and developed, the species compositions of the queen and worker bee microbiomes changed and the workers were confirmed to have inherited specific strains from the queen. Compared with honeybee microbiomes, bumblebee microbiomes had less strain variation and simpler carbohydrate digestion–related gene profiles. confirming the host specificity of the bee gut microbiome. Although functional studies and studies on wild bee colonies are needed, this study characterizes microbe transmission in bumblebees and provides a genomic database that can be used to further investigate the gut bacteria of these pollinating insects.