Abstract
Most phytophagous species of stinkbugs have mutualistic relationships with bacterial symbionts, which are often located within specialized midgut regions called M4. Heterogastridae, previously classified within the family Lygaeidae, are now classified as a family proper; however, the symbiotic organ's morphology and symbiont identity remain unclear. We herein investigated symbiotic systems from two heterogastrid species. The results obtained show that they possess two rows of midgut crypts akin to those of Coreoidea and consistently associate with Caballeronia symbionts of the SBE-α and Coreoidea clades. The present study clearly demonstrates that Caballeronia bacteria are symbionts of Heterogastridae and is the first to report a Coreoidea clade symbiont from the superfamily Lygaeoidea.