Rhyacophila caussensis Valladolid & Arauzo & Coppa & Reding & Dorda & Rey 2025, sp. nov.

Rhyacophila caussensis Valladolid & Coppa, sp. nov. Introduction: This species has been found in southern France, in the Aveyron department. Derivatio nominis: Derived from the name of the area where the new species has been found, the Grands Causses, a set of high calcareous plateaus that extend across the south of the Massif central of France. Material Examined: Holotype ♂: FRANCE (CAU 2), river La Sorgue, source, Cornus, Aveyron, 43.877ºN, 3.205ºE, 574 m a.s.l., 20/vii/2013, leg. G. Coppa [T5587 (OPIE)]. Paratypes: FRANCE, 1 ♂, river La Sorgue, source, Cornus, Aveyron, 20/vii/2013, (G. Coppa) [T5587 (OPIE)]; 1 ♂ + 1 ♀, river Le Cernon, Saint Rome de Cernon, Aveyron, 21/vii/2013, (G. Coppa) [T5580 (OPIE)]. ADULT Figs 2–4 Colour: Specimens preserved in ethanol reddish brown dorsally, yellowish ventrally, spurs brown, setae brown, females generally darker than males; small black or dark brown spots in dorsal area. Forewings (Fig. 2a) dark, each with small pale spots, two central transversal dark band (fascia) in distal area more or less conspicuous, with dark thick stigma (St) on leading edge between subcostal (Sc) and first radial (R 1) veins, hyaline circular zone in connection area of medial (M) and m-cu crossvein, crossveins connecting R 1 +R 2 (r) and fifth radial (R 5), and first medial (M 1) veins (r-m) present, crossveins connecting first (A 1) and second anal (A 2). Hind wings (Fig. 2b) pale, each with dark thick stigma on leading edge between subcostal (Sc) and second radial (R 2) veins; proximal segments of medial vein (M) conspicuous, median crossvein m connecting M 2 and M 3+4 veins present; crossveins between fifth radial (R 5) and median vein (M) and between cubital Cu 1a and median vein (M) present; proximal segment of first cubital (Cu 1a-b) thicker. MALE Biometrics: Type series: Lengths: Body (distance from front of head to distal edge of segment IX): 8.5–10.2 mm (x̄ = 9.3, SD = 0.85, n = 3), forewing 10.7–12.0 mm (x̄ = 11.3, SD = 0.67, n = 3), hind wing 9.5–11.5 mm (x̄ = 9.9, SD = 0.56, n = 3). Holotype male Lengths: Body, 10.2 mm, forewing 11.1 mm, hind wing 9.7 mm. Genitalia (Figs 3, 5): 2nd segment of each inferior appendage (Figs 3A, 5a) with posterior edge slightly convex in centrodorsal area, ventral edge slightly convex, more than 2 times longer that dorsal edge; apicodorsal vertex of 2nd segment ~ 135° and round, apicoventral angle ~ 60°, projecting as thick lobe tapered to round apex. Parameres in ventral view curved posteromesad in distal half (Figs 3 BV, p; 5c). In lateral view (Figs 3 BL, 5d) each constricted 1/3 distance beyond base, dilated at middle, with round dorsal and ventral margins; along midventral margin two-three long, thick spines; midlateral surface with sparse spicules or setae, from middle posterodorsal to subposteroventral edges, decreasing slightly in size from ventral to dorsal edges. Aedeagus (phallicata) in lateral view (Fig. 3 CL) with anterodorsal margin and posterior corner of dorsal concavity hooked anterad, apical edge of aedeagus concave; ventral lobe of aedeagus in ventral view triangular, with round apex (Fig. 3 BV, vl), in lateral view vertical edge concave, posteroventral angle almost 90º (Fig. 3 CL). In dorsal view posterior edges of lateroventral lobes of phallus apically convex, apicolateral margins round (Fig. 3 CD, lvl). Apicodorsal lobe of segment IX in dorsal view hexagonal, with maximum width in central area (Figs 3 DD, al; 5b), with apicomesal excision; preanal appendages (Fig. 3 DD, pa) rectangular, 3/4 as long as apicodorsal lobe, round subapically and posterior edges convex. In ventral view, apical band pentagonal shaped (Fig. 3 DV, ab), longer than wide, its posterior arms parallel and round apically, its non-sclerotized mesal area triangular (Fig. 3 DV, va), anal sclerites triangular, posterior edges straight or slightly convex (Fig. 3 DV, as). FEMALE Biometrics: 1 female. Body length (distance from front of head to distal edge of segment VIII): 10.4 mm, each forewing 12.5 mm, each hind wing 10.9 mm. Genitalia (Figs 4, 7): In lateral view (Figs 4L, 7L), posterior margin of segment VIII valves on each side with three projections (dorsal, posterior and ventral) of similar size, margin oblique from dorsolateral to ventrolateral projections. In dorsal view (Figs 4D, 7D), with indentation between segment VIII valves enclosed by pair of dorsolateral triangular projections, with rounded apical and subapical corners, delimiting oval space. In ventral view (Figs 4V, 7V) segment VIII valves forming two elongate sclerites, concave, diverging and separated basally; intersegmental membrane with pair of pale, ovoid or slightly elongate sclerites. Diagnosis of males of Rhyacophila caussensis, R. fasciata and R. septentrionis Genitalia: In R. caussensis (Fig. 5a) the posterior edge of the second segment of each inferior appendage is concave in the middle and the ventral edge is more than 2 times longer than dorsal edge. In R. fasciata the posterior edge of the second segment of each inferior appendage is slightly concave dorsally and convex ventrally and the ventral edge is less than 2 times longer that dorsal edge (Fig 6a). In R. septentrionis, (Fig. 23a) the posterior edge of the second segment of each inferior appendage is slightly concave in the dorsal area and the ventral edge is about 2.2 times longer than dorsal edge. In R. caussensis the posterior edge of aedeagus is concave in lateral view (Fig. 3 CL); the ventral lobe of aedeagus is triangular, with the apex round (Figs 3 BV, vl; 5c), in lateral view angled, almost 90º (Fig. 3 CL); posterior edges of lateroventral lobes of phallus are convex; the apicolateral margins are rounded and the lateral margins are diverging anteriorly. In R. fasciata the posterior edge of aedeagus is straight, projected posteroventrad, and rounded at its posteroventral apex (Valladolid et al. 2021, fig. 12CL); the ventral lobe of aedeagus is subtriangular and round posteriorly (Fig. 6c); the lateroventral lobes of the phallus are straight, its posterior edges convex, apicolateral margins rounded. In R. septentrionis the posterior edge of aedeagus is straight and projected posteroventrad in a small ventral apex in lateral view (Fig. 19 CL); the ventral lobe of aedeagus is semicircular with the apex pointed (Figs 19 BV, vl; 23c), in lateral view a small projection in posteroventral angle (Fig. 19 CL); posterior edges of lateroventral lobes of phallus are convex; the apicolateral margins are rounded. In R. caussensis the apicodorsal lobe of segment IX in dorsal view (Figs 3 DD, al; 5b) is hexagonal, with its maximum width in the central area, with deep apicomesal excision; the preanal appendages are rectangular, with posterior edges convex; the apical band in ventral view (Fig. 3 DV, ab) is pentagonal shape with its posterior arms parallel and directed posterad; the non-sclerotized mesal area (Fig. 3 DV, va) is triangular; the anal sclerites (Fig. 3 DV, as) are straight or slightly convex apically. In R. fasciata the apicodorsal lobe of segment IX in dorsal view (Fig. 6b; Valladolid et al. 2021, fig. 12DD, al) is dilated subapicolaterally, almost round, with a shallow apicomesal excision in some specimens; the preanal appendages (Valladolid et al. 2021, fig. 12DD, pa) are round, convex laterally; the apical band in ventral view (Valladolid et al. 2021, fig. 12DV, ab) is pentagonal with its posterior arms widely separate and straight; the non-sclerotized mesal area (Valladolid et al. 2021, fig. 12DV, va) is heart-shaped and with a wider posteromesal excision; the anal sclerites (Valladolid et al. 2021, fig. 12DV, as) are truncated apically. In R. septentrionis the apicodorsal lobe of segment IX in dorsal view (Figs 19 DD, al; 23b) is dilated subapicolaterally, with a small apicomesal excision; the preanal appendages (Fig. 19 DD, pa) are round; the apical band in ventral view (Fig. 19 DV, ab) is V-shaped with its posterior arms almost parallel; the non-sclerotized mesal area (Fig. 19 DV, va) is oval, narrow; the anal sclerites (Fig. 19 DV, as) are concave apically. In R. caussensis the parameres in lateral view (Figs 3 BL, 5d) are dilated in the middle, each has two-three thick spines on its midventral margin; the midlateral surface has sparse spicules or setae, decreasing slightly in size from ventral to dorsal areas. In R. fasciata the parameres in lateral view (Fig. 6d; Valladolid et al. 2021, fig. 12BL) are convex basally, with almost parallel dorsal and ventral margins in central area (S-shape), each has two rows of long, thick spines on the posterior midventral margin, each row with more than three spines pointing laterad; the midlateral surface has sparse fine setae from the middle of the anteroventral edge to the posterodorsal edge, covering most of apex, but absent in the middle anteroventral and posterodorsal edges. In R. septentrionis the parameres in lateral view (Figs 19 BL, 23d) each without spines on its midventral margin, with few long, thick spines on its lateroventral area; the midlateral surface is covered by fine spicules or setae from middle to ventral edge, absent in middle anteroventral and posterodorsal edges. Diagnosis of females of Rhyacophila caussensis, R. fasciata and R. septentrionis Genitalia: In R. caussensis lateral view (Figs 4L, 7L) each of the segment VIII lateral valves has an apicodorsal projection, together with a central and posteroventral projections, extending obliquely from anterodorsal to posteroventral areas. In R. fasciata lateral view (Fig. 8L; Valladolid et al. 2021, fig. 13L) each of the segment VIII lateral valves is quadrate with an apicodorsal projection; the upper posterior margin is nearly vertical and with an irregular edge with one or two posterior sinuosities (Valladolid et al. 2021, figs 13La, 13Lb), the posteroventral margin is slightly concave sub-basally and straight or convex distally, in some specimens slightly indented posteriorly, the upper posterior margi