The Japanese Giant Hornet, Vespa mandarinia japonica, is one of the largest wasp species in the world. Its foraging behavior and interactions with the environment are driven by a highly specialized diet. The food sources used by the hornet are sharply divided between the needs of the adult workers and the demands of their developing young.
Energy Sources for Adult Hornets
Adult hornets, like other social wasps, require simple carbohydrates to fuel activities such as long-distance flights. Since the adult digestive tract cannot process solid food, their sustenance comes solely from sugar-rich liquids. Foraging workers seek out sugary secretions like tree sap, particularly from oak trees. Other external energy sources include flower nectar, honeydew secreted by aphids, and the juices of overripe fruits.
The most specialized energy source is found within the nest through trophallaxis. Adult workers exchange the protein-rich prey they collect for a clear, amino acid-rich liquid regurgitated by the larvae they feed, providing immediate fuel for hunting.
Protein Acquisition and Prey Targets
The hornet’s solid food intake is primarily protein, collected specifically to nourish the growing larvae, not the adults. Adult workers are skilled, opportunistic predators that hunt a wide variety of large insects, including mantids, large beetles, and other species of wasps and bees. They also scavenge protein from sources like animal carrion, which supplements the developing brood’s diet.
Once prey is captured, the worker uses its powerful mandibles to chew and macerate the insect’s body, typically removing the appendages and head. This process transforms the prey into a concentrated, protein-rich paste, or “meatball,” suitable for transport back to the nest. Honey bee colonies are the hornets’ most notable targets, representing a dense source of protein in the form of developing brood.
The attack on a honey bee hive proceeds in three stages: hunting, slaughter, and occupation. In the initial hunting phase, individual hornets catch bees near the entrance to acquire the adult bee’s thorax for protein paste. This transitions to the coordinated slaughter phase, where a small group of hornets can eliminate an entire colony of tens of thousands of European honey bees in a few hours. The hornets then occupy the hive for days, systematically removing the bee larvae and pupae to feed their young.
Dietary Adaptations Throughout the Colony Cycle
The hornet’s foraging priorities change throughout the year, reflecting the colony’s shifting nutritional demands. In the spring, the founding queen operates solo, requiring sugar for energy and protein from captured insects to develop the initial clutch of workers. She forages for herself and her first brood until the first generation of workers emerges.
Once workers appear in early summer, the queen focuses solely on egg-laying, and the workers take over foraging duties. Protein demand increases steadily throughout the summer as the colony grows exponentially. The most intense change occurs in late summer and autumn when the queen lays eggs that will develop into the next generation of virgin queens and males. Rearing these large reproductive individuals requires a massive input of protein, driving the mass attacks on honey bee hives during the fall. As the colony declines and new queens prepare for overwintering, their focus shifts to consuming high-sugar foods to build up fat reserves before they disperse and hibernate.