Trechus (Trechus) bouilloni Faille

Habitus as in Fig. 1.Elongated, round–sided. Body surface with a very thin, hardly visible, dense microreticulation, with more distinguishable meshes on the head. Colour. Dorsal surface dark brown, moderately shiny. Antennae, palpi and legs light brown. Chetotaxy. Surface of elytra glabrous with the exception of a periscutellar seta, two discal setae on the third stria, four humeral setae, four setae along lateral margin and two preapical setae. Marginal setae of pronotum present, the anterior ones located before the first third of the length. Ventral pubescence limited to one seta on each half sternite. Head. Eyes reduced, flat; ommatidia well defined; maximum diameter of about eight ommatidia, temples approximately twice the length of eyes, strongly wrinkled to the neck. Frontal furrows deeply impressed. Antennae moderately long, five antennomeres extend beyond the pronotal base. Antennomere III distinctly longer than antennomeres II and IV, which are similar in length. Pronotum. Proportions (M–F): WP/LP = 1.3–1.28, WP/WPB = 1.3–1.3, WP/WH = 1.38–1.3, WE/WP = 1.57–1.53. Transverse, with lateral margins finely bordered; wider in anterior part, narrower than elytra; posterior part much narrower than base of elytra. One seta in the marginal gutter at about a third of pronotum length, another one close to hind angle. Sides evenly rounded and straight just between hind angles and insertions of posterior setae. Hind angles well developed, salient. Elytra. Proportions (M–F): WE/LE = 0.65–0.69. Oval, broadest almost at mid–length; surface moderately convex, flattened on disc. Shoulders distinct but rounded. Striae very finely punctuated, sixth inner striae deeply impressed on disc, but reduced at apex and base; seventh striae shallower, but distinct, the eighth reduced to the posterior quarter of elytra. Apical striola strongly impressed continuing the fifth stria. Hind wings. Very reduced, not functional. Male genitalia. Median lobe of aedeagus slender, in lateral view (Fig. 15) the basal third curved, the central part straight and the apex showing a curved hook; assymetrical in dorsal view (Fig. 8). Parameres slender, each with 4 to 6 setae at apex. Internal sac of aedeagus with an elongate well-sclerotized piece, forming a symmetrical gut and armed with internal scales (Fig. 16). Characteristic secondary sclerotization of the sperm duct forming a kind of second copulatory piece out of the base of the median lobe (Fig. 15: CP2).

Trechus bouilloni sp. n. is only known from the type locality, the MSS of Lizarraga pass (Navarra, Spain) (Fig. 36). The type locality is a MSS located on a northern slope at the eastern extremity of the Sierra de Andía–Urbasa, close to the Lizarraga pass. Trechus were collected by means of traps in a zone of scree (altitude: 900 m) extending from east to west at the feet of cliffs of Albian limestone lining the northern slope of the plateau of the Sierra de Andía–Urbasa. This scree slope consists of a mass of fallen rocks resulting from the erosion of calcareous cliffs and constitutes a steeply sloped (45°) MSS, filling one of the numerous gullies of a beech forest covering the entire northern side of the plateau lining the southward depression of the Río Arakil (Sakana valley). On this unstable ground, beeches are replaced by grassy and mossy vegetation dotted with shrubs. The layer of humus is irregular and very thin and only partly covers the blocks of white, angular, medium–sized limestone, rarely exceeding the size of 1 dm³. The traps were placed 50 centimeters deep in a “C–type” horizon (sensu Juberthie et al. 1981), constituted mainly by stones of 5 cm³, not sealed by the ground and not welded, leaving numerous spaces between them and forming a layer several meters thick above the compact rock. The other Coleoptera collected with Trechus bouilloni sp. n. were Leiodidae, Cholevinae: Catops subfuscus Kellner, 1846, Sciodrepoides watsoni (Spence, 1813) (Catopini) and Bathysciola sp. (Leptodirini). Some specimens of Trechus bouilloni sp. n. were parasitized by an undetermined Ascomycete. Trechus bouilloni sp. n. was not found in caves of the area north of Larraona (cueva de los Cristinos, cuevas de Erbeltz, Txintxoleze, Noriturri, Akuandi, del Queso, Iniriturri, Arleze, Laminatitur), suggesting that it is strictly located in MSS (CB personal observation).