Blind life in the Baltic amber forests: description of an eyeless species of the ground beetle genus Trechus Clairville, 1806 (Coleoptera: Carabidae: Trechini).

The first eyeless beetle known from Baltic amber, Trechus eoanophthalmus sp. n., is described and imaged using light microscopy and X-ray micro-computed tomography. Based on external characters, the new species is most similar to species of the Palaearctic Trechus sensu stricto clade and seems to be closely related to the Baltic amber fossil T. balticus Schmidt & Faille, 2015. Due to the poor conservation of the internal parts of the body, no information on the genital characters can be provided. Therefore, the systematic position of this fossil within the megadiverse genus Trechus remains dubious. The occurrence of the blind and flightless T. eoanophthalmus sp. n. in the Baltic amber forests supports a previous hypothesis that these forests were located in an area partly characterised by mountainous habitats with temperate climatic conditions.