Key to the Azorean species of Trechus (modified from Borges et al. 2004) 1 Apical angle of elytra rounded..................................................................................................................... 2 - Apical angle of elytra pointed or sharp angled............................................................................................ 7 2 Larger species, length> 3.5 mm; lateral margins of pronotum markedly sinuated before the basis, degree of pigmentation variable.............................................................................................................................. 3 - Length 3.0– 3.2 mm; lateral margins of pronotum hardly sinuated before basis; clearly dark pigmented species ............................................................................................................................ torretassoi Jeannel 3 3rd antennomere subequal to 2nd ................................................................................................................. 4 - 3rd antennomere longer than 2nd .................................................................................................................. 5 4 Pronotum cordiform and highly transverse (index W/L = 1.35), with lateral furrow very narrow (epigean species) ...................................................................................... terrabravensis Borges, Serrano & Amorim - Pronotum less transverse (index W/L = 1.26); lateral furrow larger (beetles occurring in entrance of caves) ................................................................................................................. montanheirorum Oromí & Borges 5 Body depigmented with a convex and ovate aspect .................................................................................... 6 - Body pigmentation dark brown, with some lighter parts; appendages less pigmented (light brown); body more depressed ........................................................................................................... isabelae new species 6 Aedeagus with apex of lamella slightly blunt; known from Pico .................................... picoensis Machado - Aedeagus with apex of median lobe deeply curved upwards; known from Faial ......................................... .............................................................................................................. oromii Borges, Serrano & Amorim 7 Apical angle of elytra sharp (sometimes notched), forming a small protruding point; total length 3.6–4.3 mm .............................................................................................................................. terceiranus Machado - Apical angle of elytra sharp (forming a right angle); total length <3.5 mm ............................................... 8 8 Slightly pigmented on elytra and pronotal disc; aedeagus in lateral view with apex of median lobe more or less straight and pointed; left paramere with 4 setae ........................... pereirai Borges, Serrano & Amorim - Depigmented; aedeagus in lateral view with apex of the median lobe sharpened and slightly curved upwards; left paramere with 5 setae .................................................................. jorgensis Oromí & Borges

Published as part of Borges, Paulo A. V., Oromí, Pedro, Serrano, Artur R. M. & Amorim, Isabel R., 2007, Biodiversity patterns of cavernicolous ground-beetles and their conservation status in the Azores, with the description of a new species: Trechus isabelae n. sp. (Coleoptera: Carabidae: Trechinae), pp. 21-31 in Zootaxa 1478 on pages 25-26, DOI: 10.5281/zenodo.176791