Aiolopus thalassinus (Fabricius, 1781), a new grasshopper for the Nordic countries and a migrating swarm crossing the Baltic Sea

Abstract

We report the first finding of the grasshopper Aiolopus thalassinus (Fabricius, 1781) in the Nordic countries. Two migrating individuals were attracted to light at a known hotspot of migrating moths near the southernmost tip of Gotland in the Baltic Sea, 8th of August 2020. End of September hundreds of individuals had made landfall in a bay not far from the first locality. The mass occurrence followed after days of easterly or southeasterly winds, a strengthened high pressure over Russia, and an early morning with low-lying clouds. Aiolopus thalassinus is a long-winged grasshopper with strong flight capacity and a wide distribution across the Old World. It also shares some of the density-dependent behavioral and physiological characteristics of the migratory locusts. In Europe the northern continuous distribution limit stretches through south Germany and middle Poland. The findings on Gotland follow the first record in Lithuania, 2019, and a recent trend of expanding range in south Germany which indicates a species expanding its distribution due to a changing climate. The findings also show that this is a species capable of swarm migration and crossing a minimum of 170 km of open sea when winds are favorable.