Yellowjackets (Vespula and Dolichovespula) are highly efficient predators and scavengers with a complex diet. These social insects live in large colonies that can number in the thousands by late summer. Their consumption habits are dictated by the nutritional needs of the colony as it grows. A yellowjacket’s diet changes significantly depending on its life stage, focusing primarily on two distinct nutritional requirements. The question of whether they consume their own kind relates to survival instincts and colony hygiene.
Primary Food Sources
Throughout the spring and summer, rapid colony growth drives the workers’ foraging behavior. The most pressing nutritional need is protein, required to fuel the development of thousands of larvae. Adult workers actively hunt and capture live arthropods, such as flies, caterpillars, and spiders, and scavenge on fresh meat or dead insects. Workers chew this protein-rich food into a paste before feeding it to the developing brood.
Adult yellowjacket workers primarily rely on carbohydrates and sugars for energy. They obtain these sugars from flower nectar, tree sap, and fruit juices to power their demanding flight and foraging activities. This dual-diet approach ensures that both the developing young and the active workers have the necessary fuel for the colony’s expansion.
When Yellowjackets Consume Their Own
Yellowjackets do consume their own kind, but this behavior is not a regular predatory activity. This necrophagy occurs under specific conditions, often related to colony maintenance or extreme environmental stress. Workers consume or remove deceased or severely injured nestmates to maintain nest hygiene and prevent disease spread. Consuming the dead also recycles valuable protein back into the colony’s food supply.
The most notable form of consuming their own is oophagy or larviphagy (the consumption of eggs or larvae). This is generally a response to resource scarcity or the breakdown of the colony’s social structure. For example, if the queen dies or external food sources become critically low, workers may consume the remaining brood. The larvae represent a final protein source, which is a survival mechanism allowing adult workers to sustain themselves briefly when the colony structure is collapsing.
The relationship between adults and larvae involves trophallaxis, a unique food exchange often mistaken for cannibalism. Adult workers feed the larvae protein, and in return, the larvae secrete a sugary substance that the adults consume. This reciprocal feeding is a symbiotic relationship and a vital component of the yellowjacket colony’s nutritional system.
The Shift in Autumn Foraging
The workers’ foraging behavior changes dramatically in late summer and early fall, which is when the insects become most noticeable. The colony life cycle begins to wind down as the queen stops laying eggs and new larvae production decreases. This cessation of brood production has a direct impact on the adult workers’ diet.
The loss of developing larvae means workers no longer receive the sugary secretions from trophallaxis, cutting off their main carbohydrate source within the nest. The colony has simultaneously reached its maximum size, with thousands of workers and new reproductives all requiring energy. The workers’ nutritional focus shifts entirely to finding external sources of high-energy sugars to sustain themselves.
This desperation for carbohydrates leads workers to aggressively scavenge for sweet foods and beverages near human activity, such as at picnics and garbage cans. They become more persistent and likely to sting because their internal food source has disappeared. This late-season behavior is a forced survival response to the natural end of the yellowjacket’s annual life cycle, occurring before cold weather kills the non-hibernating members.