Student finds rare water beetle breeding on Saaremaa

A student has discovered a breeding population of the rare Lapland diving beetle on Saaremaa, an island in Estonia, ERR reported. The species had not previously been recorded there.

Riste Nellis, a student at Kuressaare Hariduse School, studied diving beetles on Saaremaa and nearby Muhu during field trips organised by the Estonian Environment Agency in the summers of 2024 and 2025. Her research found six species in the Dytiscus genus and three in the Graphoderus genus on Saaremaa.

The Lapland diving beetle (Dytiscus lapponicus) was found breeding in a lake. The species is rare on mainland Estonia and had previously been recorded in the country mainly in bog pools. Nellis also found a breeding population of the western diving beetle (Dytiscus semisulcatus) in western Saaremaa. A survey in 2016 and 2017 did not find that species on the island.

The heart-shaped diving beetle was the most numerous and widespread of the large diving beetles recorded in the study. The broad diving beetle was also widely distributed in western Saaremaa, where the researchers found more suitable water bodies.

Diving beetles are predatory insects that live mainly in shallow, plant-rich standing water or water with a weak flow. The Environment Agency began monitoring the beetles in 2024 to collect information about their distribution and numbers.