Mosquito Numbers Low in Southern Finland but Heavy Rains Could Bring Surge
Mosquito activity has been unusually low this summer in southern, central, and eastern Finland, but recent heavy rains may soon change that. According to experts, the dry spring and low-snow winter contributed to the scarcity, though other factors—such as predators, diseases, and environmental conditions—also play a role.
Marko Mutanen, a professor and entomologist at the University of Oulu, explains that mosquito populations fluctuate naturally and cannot be predicted based on a single season. "They may have their own diseases, predators, and other factors affecting their numbers. And there are environmental factors whose impact we do not yet understand," he says (Helsingin Sanomat). The insects lay their eggs in damp depressions like ditches and bogs, where they remain dormant until submerged in water. If conditions are too dry, the eggs can stay underground for years before hatching.
While southern Finland has seen fewer mosquitoes, other regions have not. Mutanen notes that Åland and the Oulu area have had "commendable" numbers, while Lapland’s mosquito season has been more abundant than usual (Helsingin Sanomat). However, recent rainfall may now trigger a surge in the south. "Now that warmer weather is arriving, the development of mosquito eggs is very rapid. In summer, mosquitoes develop from egg to adult in just a few weeks," Mutanen tells Ilta-Sanomat.
The species now emerging are so-called summer mosquitoes, which overwinter as eggs and typically hatch around July or August. Puddles and temporary water bodies created by rain provide ideal breeding grounds. "It would not be at all impossible for mosquitoes to become a nuisance in the south as well," Mutanen warns (Ilta-Sanomat).
Despite their irritating bites, mosquitoes serve an important ecological role. They are a food source for birds, bats, and dragonflies, and their decline could disrupt local ecosystems. "Even if removing one component does not yet collapse the entire ecosystem, it would cause a disturbance in it," Mutanen emphasizes (Helsingin Sanomat). The mosquito season is expected to continue for some time, with numbers potentially rising in the coming weeks.