Summer heat draws wasps to outdoor food, increasing human encounters

In the high summer months, wasp activity reaches its peak. The common wasp (Vespula vulgaris) and the German wasp (Vespula germanica) form colonies that can contain hundreds to several thousand workers, each living only 6–8 weeks. Queens are the only individuals that overwinter and start new nests in spring.

As natural nectar and insect prey become scarce in hot weather, these wasps turn to human food sources rich in sugar and protein—cakes, pastries, grilled meat, and other outdoor snacks. Their attraction is driven by the need for energy and water, not by increased aggression. Wasps sting only when they feel threatened or when their nest is disturbed, regardless of temperature.

Entomologists, including Dr. Joachim Eberhardt of the Naturschutzbund NRW, note that the perception of greater aggression is a myth; more wasps are simply visible because of larger numbers and the abundance of food at picnics and barbecues. Research at the University of Graz on Polistes wasps shows that higher temperatures raise their metabolic rate, forcing them to forage more intensively, which further amplifies human‑wasp encounters.