Wasps and hornets (large members of the Vespidae family) are insects whose feeding habits are complex and often misunderstood. Their diet changes dramatically between the adult and larval life stages, reflecting two completely different nutritional needs. This distinction between the high-energy demands of the mature flier and the protein requirements of the developing young is central to their survival strategy. Understanding this dual dietary nature reveals the complexity of their lives and their role in the ecosystem.
The Adult Energy Source: Sugars and Fluids
Mature, flying wasps and hornets require a diet rich in simple carbohydrates to fuel their highly active lifestyles. Their primary energy source comes from various liquid sugars found in their environment, which are easily digested and quickly converted into flight fuel. They commonly consume flower nectar, tree sap, and the sugary liquid known as honeydew, which is excreted by aphids and other plant-sucking insects.
The adult digestive system, specifically a narrow midgut, limits their ability to process solid foods, including the protein-rich prey they hunt. This anatomical constraint necessitates a liquid diet, which is why they are often attracted to human foods like ripe fruit, sodas, and juices, particularly later in the summer. This shift to external sugar sources occurs as the colony’s protein demands decline, prompting adults to forage widely for carbohydrates.
The Larval Growth Requirement: Protein and Prey
In stark contrast to the adults, wasp and hornet larvae require a diet heavily focused on protein for rapid growth and development. The sessile larvae, confined to the nest cells, are carnivorous and depend entirely on the adult worker wasps for their sustenance. Worker adults forage relentlessly, hunting and killing a variety of arthropods, including flies, spiders, and especially soft-bodied insects like caterpillars.
The captured prey is then meticulously masticated by the adult workers, transforming the solid protein into a paste or pellet that is small enough for the larvae to ingest and digest. This process is part of a symbiotic nutritional exchange called trophallaxis, which is fundamental to the social colony structure. After consuming the protein, the larvae secrete a nutrient-rich droplet containing free amino acids and simple carbohydrates, which is readily consumed by the attendant adults.
This larval secretion acts as a source of maintenance nutrition for the adult workers, who are primarily carbohydrate-dependent. The exchange ensures that the young receive the necessary protein for development, while the adults gain a liquid source of nutrients they cannot efficiently process from solid prey. The amino acid content in this larval saliva is often significantly higher than in floral nectar, highlighting its importance to the adult diet.
Ecological Role: Wasps and Hornets as Predators
The protein requirements of the larvae establish wasps and hornets as effective generalist predators within their ecosystems. Their constant need to provision the developing young means a single colony can eliminate thousands of pest insects over a season. This predatory activity functions as a significant form of natural pest control, benefiting both natural habitats and agricultural settings.
Wasps prey on common crop-damaging species, such as specific caterpillars that feed on foliage and various species of flies. By regulating the populations of these herbivorous arthropods, wasps contribute to the overall health and balance of plant communities. While they are not as efficient as bees, adult wasps also contribute to pollination as they move between flowers and plants in search of nectar to fuel their foraging flights.
Dietary Nuances: Social Versus Solitary Feeders
Wasp feeding strategies are diverse, depending on whether the species is social (living in a large colony) or solitary (living independently). Social species, including hornets and yellow jackets, are opportunistic generalists, hunting a broad range of insect prey to meet the collective needs of their colonies. Their foraging behavior focuses on acquiring a high volume of biomass to support the many larvae in the nest.
Solitary wasps, such as mud daubers and spider wasps, display a specialized hunting strategy. A female solitary wasp often hunts only one specific type of prey, such as a particular species of spider or caterpillar, which she paralyzes with her venom. This single, living, paralyzed victim is then sealed into a nest cell with a single egg. This provides a fresh, protein-rich meal for the larva immediately upon hatching.