Re-discovery of Leptochilus quintus Gusenleitner from Mosor Mountain, Croatia (Hymenoptera; Vespidae), after 136 years of presumed extinction

Six males of Leptochilus quintus Gusenleitner were collected in May 2021 on Mosor Mountain in Croatia. This species was assumed to have become extinct since no specimens were collected during the past 136 years. In contrast to the only previously known (holotype) specimen with an entirely black clypeus, the specimens examined have variable amounts of yellow markings on the clypeus, and only one specimen has an entirely black clypeus. Two specimens were sequenced for the mitochondrial COI gene, revealing that their sequences differed in two base pairs and suggesting a certain level of retained genetic diversity in the population. This finding suggests the need for a more detailed faunistic analysis of Croatia and the entire Balkans as an intersection of Central, Eastern and Southern European faunistic elements.