Wasp Season in Switzerland: the Yearly Calendar

Spring: the queen starts from scratch

Every wasp season begins with a single, already mated young queen that has survived the winter on her own — hidden in dead wood, wall crevices or roof cavities. As soon as it turns warm enough in April or May, she looks for a nesting site and builds a small, fist-sized primary nest entirely from scratch. There she lays the first eggs and cares for the brood completely on her own, until the first workers hatch and take over the work from her. Anyone who spots a single, large wasp in the house or garden at this stage is usually looking at exactly this founding queen — more on this in the guide Spotting a wasp queen in spring. Incidentally, a large proportion of these primary nests fail of their own accord, for instance because the location is unsuitable or because the queen does not survive the founding phase.

Summer: the colony grows quickly

From June onwards the workers take over nest building, foraging and brood care, while the queen concentrates solely on laying eggs. The colony now grows fast: a few dozen insects turn into several hundred within a matter of weeks. If the original cavity becomes too cramped, the wasps sometimes move into a larger secondary nest in July or August — a behaviour observed primarily in hornets, and one that can make a nest appear to pop up overnight in a new spot.

Late summer: peak size and greatest risk

In August and September a colony reaches its maximum size and, at the same time, its most aggressive phase. Food becomes scarcer, the craving for fruit increases, and nests are defended in no uncertain terms. Workers react particularly irritably when their queen dies and the colony becomes “queenless” — a state that, without the calming influence of the queen, leads to heightened nervousness throughout the whole colony. The guide Why are wasps so aggressive in August explains exactly why these weeks are so delicate.

Autumn: the end of the season

With the first cold nights the social structure collapses: the old queen and all the workers die, and only the freshly hatched, mated young queens retreat to their winter quarters. The abandoned nest is never colonised again, because every surviving young queen founds her own new primary nest the following spring. The guides When do wasps die in autumn and How long does a wasp colony live provide the details. Anyone who discovers an empty nest on their house will find answers on whether it needs to be removed in the guide Wasp nest in winter, and anyone wondering whether it will ever be re-occupied should read the guide Do wasps return to an old nest. For acute problems during the season, a specialist can help via /wespennest-entfernen.