Distoleon tetragrammicus (Fabricius, 1798) a new antlion for the Nordic countries with an illustrated identification key to species (Neuroptera: Myrmeleontidae)

Abstract

We report the first finding of the antlion Distoleon tetragrammicus (Fabricius, 1798) from Sweden. Several adults of the species have been collected or photographed on the island of Gotland in the Baltic Sea, between 2017 and 2021. The first finding is from Tofta skjutfält, a sandy military training ground vegetated with pines and mixed forests on the west coast of Gotland. Based on multi-year observations at the same locality as well as video recording of an egglaying female it is clearly a resident population, even though larvae are yet to be documented. Distoleon tetragrammicus is not previously known from any of the Nordic or Baltic countries. The species is common in southern Europe with a wide distribution across west palearctic and becomes rarer towards central Europe. The closest known locality is an outpost population on the Hel peninsula on the Polish Baltic coast which we speculate is the most probable source, 240km south of Gotland across the Baltic sea. Previously but three species of antlions were known from the Nordic-Baltic countries, all belonging to the typical pitfall trap-building tribe Myrmeleontini and subfamily Myrmeleontinae: Myrmeleon formicarius (Linnaeus, 1767), Myrmeleon bore (Tjeder, 1941) and Euroleon nostras (Geoffroy in Fourcroy, 1785). Distoleon tetragrammicus belongs to subfamily Nemoleontinae (tribe Nemoleontini) with larvae being ambush predators without the behaviour of building pitfall traps. We provide an identification key, as well as studio and field photographs of all four Nordic species. The quality and conservation value of Tofta military training ground locality for insects is discussed with reference to other rare species.