"Something seems to have been off since the second half of spring," Õunap said on Vikerraadio's "Vikerhommik" on Friday. He said that both his own observations and reports from other enthusiasts point to fewer butterflies overall.

"We're not just talking about fewer of one or a few species — all butterflies are down: butterflies and moths, forest and meadow species," Õunap continued. "So there must be something that's affecting all of them equally."

Researchers believe Estonia's cold spring this year disrupted butterfly development. While early spring species appeared even ahead of schedule following a mild winter, chilly weather in May and June delayed growth for others.

Õunap explained that butterflies in pupal or advanced larval stages struggled during the prolonged cold, and many failed to reach adulthood.

Butterfly bust has broader impacts

Standardized monitoring confirms the drop. Light traps are used annually in the same spot for moths, while fixed transects track butterflies — consistent methods that make year-to-year comparisons possible.

But the decline has wider ecological implications. "Butterflies do play a role in pollination," Õunap said, although they're not considered as crucial as bees or flies.

Caterpillars also serve as a major food source for birds and other insectivores, which may suffer if the butterfly population crashes. Even so, he added that as he is not an ornithologist, he can't assess the impact on birds directly.

Bad weather for some, good weather for others

Despite the struggles butterflies have been facing, other insect groups appear to be thriving. Õunap has observed that true bugs, flies and insects in the hymenoptera order, including wasps and bees, seem plentiful this year, and wet conditions are especially favorable for species like mosquitoes and horseflies, whose larvae develop in water.

"The more water and small puddles there are, the more places they have to lay their eggs, and the more room the larvae have to develop," he explained, adding that such a wet year could actually help these insects thrive.

Despite this year's downturn in butterflies, Õunap is optimistic. "A typical female butterfly lays about a hundred eggs or more," he said. "If conditions improve even a little, populations can rebound quickly."

The entomologist noted that past records show butterfly numbers can vary up to threefold from year to year, and they've recovered even after really bad years.

"I really hope that's how it'll go this time too," he added.

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