The “White-faced Hornet” is the common name for the Bald-faced Hornet, Dolichovespula maculata. This large, black and white species is technically an aerial yellowjacket wasp known as a fierce predator and defender of its large, papery nest. Understanding the diet of these social wasps requires separating the nutritional needs of adult workers from those of the developing young. Their highly specialized diet shifts dramatically throughout the life of the colony.
Adult Hornet Energy Sources
Adult Bald-faced Hornet workers require a constant supply of simple sugars, or carbohydrates, to fuel high-energy activities like flying, foraging, and nest construction. Their digestive systems are not designed to break down solid protein, so they seek liquid energy sources in the environment. These sources include plant-based liquids such as flower nectar, which makes them minor, incidental pollinators as they forage.
They also readily consume tree sap exuded from wounded bark, the juices of over-ripe or damaged fruit, and a sugary substance called honeydew, which is secreted by aphids. As the season progresses, adults shift toward scavenging and will be drawn to human food sources like spilled sodas, picnic items, and fermentation products. This carbohydrate-rich diet sustains the workers, but it cannot support the growth of the next generation.
Prey Captured for Larval Development
The primary purpose of the adult workers’ foraging efforts is to secure protein for the colony’s larvae, which are the only members capable of digesting solid food. These workers are highly effective hunters, preying on a wide range of soft-bodied arthropods and other insects. Common prey items include flies, such as deer flies and horseflies, as well as garden pests like caterpillars and spiders.
Once a worker captures prey, they perform a process called malaxation, where they use their mandibles to chew the insect into a soft, digestible paste. This macerated protein is then carried back to the nest and fed directly to the developing larvae. In return for this protein meal, the larvae secrete a sugary, saliva-like liquid that the adult workers consume. This reciprocal exchange, known as trophallaxis, provides the adults with a temporary energy supplement.
Seasonal Changes and Ecological Impact
The nutritional focus of the colony changes significantly as the year progresses, driven by the size of the brood. During the spring and early summer, protein is in high demand to support the rapidly growing population of larvae, making the workers intensely predatory. This intense hunting period provides a valuable service by controlling populations of many common pest insects, giving the species a beneficial role in the ecosystem.
By late summer and early fall, the number of larvae begins to decline as the colony prepares for winter, which in turn reduces the supply of sugary larval secretions. With less protein needed for the young and a dwindling energy supply from the nest, the adult workers shift their focus entirely to external carbohydrate sources. This is when they become most noticeable and can be a nuisance, aggressively scavenging for sweet liquids and human foods before the first hard frost signals the end of the colony’s annual cycle.