Behaviour 2019
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Linking gland morphology to the recruitment behavior of a giant Asian hornet (Vespa soror)
Heather Mattila1, Johan Billen2, Satoshi Shimano3, Lien Nguyen4, Erica Maul1, Gard Otis5. 1Wellesley College, Wellesley, MA, United States; 2KU Leuven, Leuven, , Belgium; 3Hosei University, Tokyo, , Japan; 4Vietnamese Academy of Science and Technology, Hanoi, , Vietnam; 5University of Guelph, Guelph, ON, Canada

Vespa soror is the largest hornet in Vietnam and the sister species of the Asian giant hornet, Vespa mandarinia. Both hornet species are notorious for the group attacks that these predators launch on their prey, which are often other colonies of social insects. These attacks begin with a scouting hornet marking the nest and nearby vegetation of a potential prey colony to recruit nestmates to it. It has been widely assumed that hornets transfer glandular secretions to surfaces around prey nests when they rub their abdomens on them, and that these secretions act as pheromones that guide colony members to the correct location to begin a coordinated attack. However, this recruitment behavior has not been well characterized for either species, nor have the abdominal glands of giant hornets been examined in detail. We report field observations made in Vietnam of the behavior of V. soror workers as they recruit nestmates to attack Asian honey bees (Apis cerana). We pair these observations with the first morphological description of V. soror's van der Vecht and Richards’ glands, two abdominal glands of workers that are potential sources of target-marking pheromones in this giant hornet.