Wasps do eat flies, but this interaction is driven by the needs of the colony’s young. When an adult wasp catches a fly, it is hunting protein not for itself, but for the growing members of its family. Flies and other soft-bodied insects provide the necessary protein for the next generation of wasps to develop successfully. This predatory behavior solidifies the wasp’s place as a significant participant in the natural control of insect populations.
The Wasp Diet: Adults vs. Larvae
The dietary requirements of a wasp change as it transitions from a larva to an adult. Adult wasps, or imagoes, require easily digestible carbohydrates to fuel their high-energy lifestyle. They acquire these sugars from sources like flower nectar, tree sap, or honeydew secreted by aphids. The adult digestive system is adapted to process these simple sugars for flight and other activities.
Wasp larvae require a diet rich in protein for growth within the nest. Adult worker wasps must hunt and provision these proteins, commonly targeting flies, caterpillars, and spiders. After the adult feeds the protein bolus to the larva, the larva secretes a sweet, carbohydrate-rich droplet in return. This exchange, known as trophallaxis, provides the adult with necessary carbohydrates.
Hunting and Processing Prey
The pursuit and capture of a fly involve specialized hunting strategies that vary between different types of wasps. Solitary wasps, such as mud daubers, often subdue their prey with a precise sting that delivers venom to paralyze the fly, keeping it fresh for their single, developing larva. Social wasps, including yellowjackets and hornets, generally use their powerful mandibles to capture and kill the fly instead of relying on the stinger for immediate paralysis.
Once the prey is secured, the adult wasp begins chewing the fly to prepare the protein for transport back to the nest. The wasp uses its mouthparts to discard indigestible parts like the wings, legs, and head at the capture site. This process reduces the fly into a manageable, protein-dense bolus, which is lighter to carry in flight. This preparation ensures efficient delivery of the protein to the larvae.
Wasps as Natural Pest Control Agents
The wasp’s predatory focus on flies gives it an important role in natural pest management. Social wasps effectively control populations of house flies, blow flies, and fruit flies by hunting and feeding them to their young throughout the summer months. Their constant need for protein makes them highly effective generalist predators in many ecosystems.
Beyond predatory species, parasitic wasps, or parasitoids, are even more specialized fly controllers. These tiny wasps target the fly’s immature stages, such as the pupa or maggot. Species like Muscidifurax raptor lay an egg inside the fly’s pupal case, and the resulting larva consumes the developing fly from the inside out, preventing the adult fly from emerging. This demonstrates the comprehensive pressure wasps apply to fly populations by targeting both adult flies and their young.