Larvae of flower longicorn beetles (Coleoptera: Cerambycidae: Lepturinae) are known to be xylophagous (woody-material feeder). Wood is difficult for most animals to digest due to large amounts of indigestible polymers (e.g., cellulose, hemicelluloses, and lignin), but flower longicorn beetles are considered to be able to utilize it as food with the aid of symbiotic yeasts. Despite the marked diversity (>1500 species in 210 genera) and worldwide distribution of Lepturinae, understanding of the beetle-yeast association is limited to a small number of species. To determine the specificity of host-symbiont association, we investigated the flower longicorn beetles in Japan comprehensively. In this talk, we will introduce (1) the relationships between larval food use and yeasts and (2) geographic variation of beetle-yeast associations.