Larval development and feeding patterns of the invasive Asian longhorned beetle (Anoplophora glabripennis) in South Carolina

Asian longhorned beetle [Anoplophora glabripennis (Motschulsky), ALB] is an invasive wood-boring beetle in North America. ALB is problematic in both its native and non-native ranges because the larvae feed on the phloem and xylem of host trees, altering tree health and water movement, and causing breakage and often tree mortality. As ALB larvae develop, they transition from creating galleries in the phloem to feeding within the xylem, though it is unknown when the shift occurs and what prompts this transition. ALB is primarily univoltine in South Carolina, but phenology models indicate that a small proportion of individuals may complete development in less than a year or between one and two years. These phenology models help us better manage ALB and predict invasion risk; however, they typically rely on ambient air temperatures or estimate the under-bark temperatures where larvae live. Since host trees are known to buffer temperature extremes for the insects feeding inside them, we examined temperatures ALB larvae experience within the tree’s microclimate and compared these temperatures to the morphometric changes of ALB larvae throughout several years in South Carolina. Our results indicate that ALB larvae quickly progress to later instars, when they begin feeding in the xylem. The larvae remain a relatively consistent size throughout the winter and spring, suggesting that the larvae are going through a diapause phase which would result in a more synchronized emergence in the summer. These results improve our understanding of ALB development which supports risk modeling and management of this invasive beetle.