Wasp activity surges indoors as summer heat persists in southern Finland

This summer has seen a significant rise in wasp activity, particularly in southern Finland, where species such as the common wasp and the German wasp have thrived due to the extended warm season. Reports indicate that wasps have frequently strayed indoors, although typically not in large swarms. Specialist researcher Jouni Sorvari from the Natural Resources Institute Finland explains that while it’s uncommon to see them in such numbers, he receives reports of these incidents annually.

Wasp intrusions into homes often occur through small openings, such as spaces above refrigerators, and in just three weeks, some households reported hundreds of wasps. The question arises: what drives wasps to enter homes in droves? Sorvari notes that with outdoor temperatures at around five degrees Celsius and indoor temps at 22 degrees, the choice is clear for them.

During the summer, abundant food sources such as mosquitoes have been available, but as autumn approaches and nectar from flowers dwindles, kitchen aromas may attract them indoors. In the past few weeks, larger numbers of worker wasps invaded homes as nighttime temperatures began to drop, likely confusing them and causing them to stray from their usual routes.

The German wasp, which has only spread into mainland Finland in recent decades, has established substantial colonies, sometimes with up to 7,000 individuals. While the presence of these wasps may be troubling, Sorvari reassures that they are not particularly aggressive unless provoked. The wasp population fluctuates yearly, with higher numbers often found in even-numbered years, but the exact reasons for this pattern remain unclear.