The hornet, belonging to the genus Vespa, is a large social wasp distinguished from yellow jackets by its robust body and darker coloration. Hornets, including species like the European hornet and Asian giant hornet, have a complex diet that shifts dramatically between adult workers and their developing young. Understanding their diet requires differentiating between the high-energy needs of flying adults and the protein demands of the growing colony brood.
Fueling the Adult Hornet (Sugars and Liquids)
Adult worker hornets require simple carbohydrates for the energy demands of flight and nest maintenance. Their digestive systems are adapted to process liquids, meaning solid protein is indigestible for the workers. Adult hornets forage heavily for sugary fluids as immediate fuel sources.
These carbohydrate sources include natural liquids like tree sap, nectar, and honeydew produced by aphids. They are also attracted to overripe or damaged fruits, such as grapes, peaches, and apples, which offer high concentrations of simple sugars. Hornets also need water for hydration, cooling the nest, and mixing with wood pulp for nest construction.
A significant portion of the adult hornet’s energy comes indirectly from the colony’s larvae. This nutritional exchange ensures the workers have the necessary fuel to continue foraging and maintaining the colony. The adult diet is specialized for immediate energy.
The Protein Requirement for Larvae (Prey and Hunting)
While adults need carbohydrates, the growing larvae require a constant supply of protein to develop into mature workers, drones, and new queens. Adult workers become dedicated hunters, capturing a wide range of invertebrate prey, including large flies, caterpillars, spiders, and honey bees. This predatory behavior is essential because the larvae function as the colony’s digestive center for protein.
After capturing prey, the adult hornet uses its mandibles to dismember the catch. The resulting protein-rich mass is masticated into a semi-liquid paste digestible for the young. The adult worker then feeds this prepared protein directly to the larvae residing in the nest cells.
In a biological partnership called trophallaxis, the larvae secrete a droplet of sugary liquid in return for the protein meal. This larval saliva is rich in carbohydrates and free amino acids, such as proline, which is an efficient metabolic fuel for the adults. This exchange ensures adults receive energy to hunt and larvae receive protein for growth.
Late Season Dietary Changes
The balanced nutritional cycle shifts in the late summer and early fall when the queen stops laying eggs. As the current brood matures and emerges as adults, the number of larvae providing sweet trophallactic secretions declines rapidly. This loss of the internal sugar source forces the remaining adult workers to seek external carbohydrates more aggressively than during the peak summer months.
The workers, including newly emerged males and future queens needing to store fat reserves, begin intense scavenging for easily accessible sugars. They are strongly drawn to human-associated sources, such as fallen fruit, sugary drinks, and garbage containers where fermentation is occurring. This shift often leads to the perception of increased hornet aggression, as the colony’s internal food supply collapses and workers become desperate for energy before the colony naturally declines.