Rhycophila lignumvallis Graf & Rázuri-Gonzales, 2024

Rázuri-Gonzales, Ernesto, Graf, Wolfram, Heckenhauer, Jacqueline, Schneider, Julio V. & Pauls, Steffen U., 2024, A new species of Rhyacophila Pictet, 1834 (Trichoptera, Rhyacophilidae) from Corsica with the genomic characterization of the holotype, ZooKeys 1218, pp. 295-314 : 295-314

Rhycophila lignumvallis Graf & Rázuri-Gonzales sp. nov.

Holotype.

France • ♂; Corsica, bridge over the river Vecchio near the confluence with the river Tavignano ; 42.2275 ° N, 9.24306 ° E; 195 m a. s. l.; 25 Jul. 2019; col. W. Graf leg.; in ethanol; SMF ( SMFTRI 00018634 ).

Diagnosis.

Rhyacophila lignumvallis sp. nov. (Figs 4 , 5 A, B ) belongs to the Rhyacophila tristis species group ( Schmid 1970). It is most similar to R. pubescens (Fig. 5 C, D ), R. tsurakiana (Fig. 5 E, F ), R. ligurica Oláh & Vinçon, 2021 (in Oláh et al. 2021, figs 55–57 therein), R. harmasa Oláh & Vinçon, 2021 (in Oláh et al. 2021, figs 52–54 therein), and R. abruzzica Oláh & Vinçon, 2021 (in Oláh et al. 2021, figs 49–51 therein), but R. lignumvallis sp. nov. is distinguishable from these species by the shape of tergum X, the dorsal arm of the phallic apparatus in lateral and ventral views, the shape of the aedeagus and parameres, and the second segment of the inferior appendages.

The dorsal surface of segment X is convex in all these species but narrower and higher in the new species, R. tsurakiana , and R. harmasa . In dorsal view, however, the new species has a slightly membranous, mesally notched, and inflated segment X, while segment X in R. tsurakiana appears flatter. Additionally, the dorsal branch of tergum X is rounded and broader in the new species, while it is narrower in R. tsurakiana and R. harmasa .

The dorsal appendix of the phallic apparatus in the new species is longer than the aedeagus and the parameres (Fig. 4 D ). This also occurs in R. harmasa , R. ligurica , R. pubescens , and R. tsurakiana but not in R. abruzzica . However, the shape of the dorsal appendix in lateral view in the new species is digitate and slightly curved dorsad, whereas R. harmasa has a slightly wider apical half, R. ligurica has a low bump mesally on its dorsal surface, and R. tsurakiana has a straight and flat dorsal appendix. In R. abruzzica , the dorsal appendage is broad and medially widened in lateral view. In comparison to R. lignumvallis sp. nov. (Figs 4 D , 5 A, B ), R. tsurakiana , and R. abruzzica , the dorsal appendix of the phallic apparatus is much longer and clearly exceeds segment X in dorsal view in R. harmasa , R. pubescens , and R. ligurica . In ventral view, the dorsal appendix is straight and rounded apically in the new species (Fig. 4 E ), slightly inflated on the apical half and rounded apically in R. harmasa , almost straight and truncate apically in R. ligurica , constricted basally and truncate apically in R. tsurakiana , and rectangular in R. abruzzica .

The aedeagus and parameres in R. lignumvallis sp. nov. are most similar to R. pubescens . However, in lateral view, the tip of the aedeagus in the new species is slenderer and slightly more curved apically than in R. pubescens . In lateral view, the parameres in the new species are broader than in R. pubescens . In ventral view, the parameres in the new species are club-shaped and curved mesad, while in R. pubescens , the parameres are digitate and directed posterad.

The second segment of the inferior appendages in the new species is triangular, with a straight dorsal margin, while all the other species have a concave dorsal margin (Fig. 4 A , 5 B ).

Description.

Adult male. Specimen in ethanol, mostly denuded; dorsally brown, ventrally light brown. Legs light brown with slightly darker tibial spurs. Head with frontal setal wart triangular; antennal setal wart subtriangular and smaller than frontal setal wart; posterior setal warts oval and connected to ocellar setal warts via a raised cuticular “ bridge ” (see Schmid, 1970; pl. I, fig. 1). Forewing length (8.8 mm, N = 1) mostly denuded, with sparse, very short light brown setae and golden brown microtrichia. Hind wings also mostly denuded, with slightly longer light brown setae. Forewing (Fig. 3 A ) with crossveins connecting costal (C) and subcostal (Sc) veins; subcostal (Sc) and first radial (R 1) veins, first (R 1) and second radial (R 2) veins (r), fifth radial (R 5) and first medial (M) veins (r-m), first medial (M) and first cubital (Cu 1) veins (m-cu), and first cubital (Cu 1) and second cubital (Cu 2) veins. Hind wing (Fig. 3 B ) with crossveins connecting subcostal (Sc) and first radial (R 1) veins, fifth radial (R 5) and first medial (M) veins (r-m), and M 3 + 4 and first cubital (Cu 1) present.

Male genitalia. Segment IX longitudinally short in lateral view (Fig. 4 A ), anterior and posterior margins slightly concave, dorsal half slightly longer than ventral. Dorsal surface of segment X membranous, slightly inflated, shallowly notched mesally in dorsal view (Fig. 4 C ). Dorsal branch of segment X short and rounded in lateral view. Anal sclerites partially fused to each other basally and to segment X, in lateral view, directed ventrad. First article of inferior appendages (Fig. 4 A ) rectangular in lateral view, slightly broader basally than apically; in ventral view (Fig. 4 B ), slightly broader apically than basally, with a small setose bump basally on mesal surface. Second article of inferior appendages (Fig. 4 A ) quadrangular in lateral view, dorsal and ventral margins slightly diverging, posterodorsal margin straight, at a 130 ° angle to dorsal margin; in ventral view (Fig. 4 B ), mitton-shaped, mesal margin with very short, peg-like setae basally and longer setae apically. Phallic apparatus (Fig. 4 D ) with dorsal appendix straight in lateral view, slightly curved dorsad, rounded apically, longer than parameres and aedeagus; in ventral view, straight, lateral margins slightly sinuous, rounded apically. Parameres in lateral view (Fig. 4 D ) broader than aedeagus, slightly curved posterodorsad, ventral margin straight, dorsal margin slightly sinuous, rounded apically; in ventral view (Fig. 4 E ), club-shaped, directed mesad. Aedeagus in lateral view (Fig. 4 D ) slender, slightly sinuous, tapering towards its apex; in ventral view, slender and straight.

Etymology.

We dedicate this species to Dr Ralph W. Holzenthal to honor his contributions to caddisfly taxonomy and systematics. Lignumvallis, wood valley, is derived from the Latin translation of Ralph’s last name.

Habitat.

The river Vecchio is a crystal-clear, slow-flowing stream with a heterogeneous bottom substrate that varies from sandy patches to gravel to boulders. Stabile substrates were densely covered by Agapetus cyrnensis pupae. As many spring trickles enter the river on its left margin and the specimen was collected by sweeping the vegetation, the habitat of R. lignumvallis sp. nov. remains unknown.

Figures

Figure 3. Rhyacophila lignumvallis sp. nov., wing venation. C, costal vein; Sc, subcostal vein; R 1 – R 5, first to fifth branches of the radial vein; M 1 – M 4, first to fourth branches of the medial vein; M 3 + 4, medial vein 3 + 4 (hindwing); Cu 1 a, anterior branch of first cubital vein; Cu 1 b, posterior branch of first cubital vein; Cu 2, second cubital vein; 1 A – 3 A, first to third anal veins; r, radial crossvein; r-m, radiomedial crossvein; m-cu, mediocubital crossvein; I – V, first to fifth wing forks; TC, thyridial cell. Scale bar: 1 mm. Illustrations were produced by Ernesto Rázuri-Gonzales.

Figure 4. Rhyacophila lignumvallis sp. nov., male genitalia, lateral view (A), ventral view (B), segment X in dorsal view (C), phallic apparatus in lateral view (D), and phallic apparatus in ventral view (E). Illustrations were produced by Ernesto Rázuri-Gonzales.

Figure 5. Rhyacophila lignumvallis sp. nov., male genitalia, dorsal view (A), lateral view (B). R. pubescens, male genitalia, dorsal view (C), lateral view (D). R. tsurakiana, male genitalia, dorsal view (E), lateral view (F). Scale bars: 100 μm. Specimens were photographed by W. Graf.