In-gallery behavior of Xylosandrus ambrosia beetles

The exotic wood boring ambrosia beetles Xylosandrus crassiusculus and X. germanus (Coleoptera: Curculionidae), native to Asia, construct galleries in the sapwood of stressed woody hosts where they culture symbiotic fungi as a food source for their offspring. Adult daughters typically disperse from their natal galleries, after mating with male siblings, to initiate new galleries. Both species attack a wide range of woody hosts and have become serious pests of orchards and ornamental nurseries, e.g., damaging infestations of X. germanus were first reported in 2013 in commercial apple orchards in western New York. Detailed studies of two other ambrosia beetles in related genera have revealed cooperative brood care by siblings and other social behaviors within the cryptic galleries, but this has not yet been studied for Xylosandrus spp. The disruption of social behaviors, if present in invasive Xylosandrus spp., could result in colony failures. Using a novel artificial diet arena, we quantified larval and adult behaviors of X. germanus. While some cooperative hygienic behaviors (cleaning and grooming) were observed, the benefit of other behaviors to other members of the gallery were unclear. For example, the early cessation of growth of the symbiotic fungus did not allow for fungal care or expansion of the fungal garden by adult siblings. Behavioral studies will continue for quantifying adult and larval behaviors of these two ambrosia beetle species.