Molecular Identification of Asian Hornet Vespa velutina nigrithorax Prey from Larval Gut Contents: A Promising Method to Study the Diet of an Invasive Pest

SIMPLE SUMMARY: The potential impact of the invasive Asian hornet on honey bee and insect biodiversity is not well understood. This study tests a method to identify what species the Asian hornet preys upon. We took the stomach contents of Asian hornet larvae and identified the prey items within those using DNA methods. The method was successful and many prey items were identified. Although the number of nests and larvae tested were small (and the results therefore had to be treated with caution), they gave an interesting snapshot of the prey items captured by V. v. nigrithorax in the UK. The method has great potential to gather further information on the diet of the Asian hornet as it expands into new areas. ABSTRACT: The Asian hornet, Vespa velutina nigrithorax (Hymenoptera: Vespidae), is an invasive hornet that was accidentally introduced into Europe in 2004. It mainly preys on other invertebrates and arthropod species, and often targets honey bee (Apis mellifera) colonies. The introduction of these hornets may damage indigenous fauna and apiculture. Knowledge of V. velutina prey preference and the species composition of their diet is relatively limited. In this study, we assessed methodologies for the molecular identification of prey using dissected larvae from destroyed nests. Ten larval samples were taken from five nests in areas where the hornets had not yet established: two from the Channel Islands and three in the mainland UK. DNA was extracted from the gut contents and sequenced and analysed by metabarcoding with Oxford Nanopore Technologies’ Flongle and MinION devices. Numerous taxa were detected in each larval sample with the species composition varying by individual and by nest. Between 15 and 26 species were found per nest, with wasps (Vespula spp.), spiders, honey bees and blow flies being the most abundant taxa. These results demonstrate that metabarcoding larval gut contents can be used to study the Asian hornet diet and give a first snapshot of the prey items captured by V. v. nigrithorax in the UK. This method could be used for future large-scale testing of the gut contents of hornet nests, in order to provide a greater insight into the foraging behaviour of this predator across Europe and elsewhere.