Residents face million-strong fruit fly swarm in Tampere, Finland

Residents of a seventh-floor apartment in Tampere, Finland, are experiencing an unusual problem: a massive swarm of tiny insects occupying the spaces between three of their windows. Milka Vuorela’s daughter, Anne Joutsimäki, estimates there could be around a million of these insects, which have appeared every autumn for the last three years.

After reaching out to both the building’s management and pest control, an insecticide treatment was attempted in early autumn. Despite these efforts, nearly all the pests remain alive. Tero Piirainen, president of the Tampere Entomologists’ Society, was surprised by the sheer number of insects but quickly identified them as autumn fruit flies, not the banana flies initially suspected. Unlike banana flies that scavenge for food, autumn fruit flies seek shelter as temperatures drop.

Video footage shows the extent of the infestation, with Piirainen noting that the flies can number in the thousands. He emphasized that this mass gathering is unprecedented in his experience, prompting curiosity about why they flock to upper floors—their preferred habitats typically being low-lying fields or parks.

The phenomenon raises questions regarding climate change, which might contribute to species like the autumn fruit fly moving into urban areas in search of milder winter conditions. These insects look for dry places to overwinter, preferring niches such as building crevices or ventilation shafts.

Piirainen also noted that eliminating them is challenging, but sealing windows may help deter their entry. Until then, residents like Joutsimäki are left waiting for colder temperatures to purge the insects from their home.