Ralph Holzenthal caddisfly (Rhyacophila lignumvallis) from Corsica in Rhyacophila tristis (Schmid 1970) group

NEWS - Ralph Holzenthal caddisfly (Rhyacophila lignumvallis Graf & Rázuri-Gonzales, sp. nov.) from the island of Corsica (France) was established as a new species in the Rhyacophila tristis (Schmid 1970) group based on morphological analysis and the mitochondrial cytochrome c oxidase subunit I (mtCOI), including sequences from 16 of the 28 species in the group.

Rhyacophila Pictet 1834 with 814 living and 30 fossil species is the largest genus of caddisflies in the world, distributed mainly in the northern hemisphere, but also in temperate and tropical India and Southeast Asia. One of the groups is the R. tristis group in the branch Rhyacophila invaria.

R. lignumvallis is most similar to Rhyacophila pubescens Pictet 1834, Rhyacophila tsurakiana Malicky 1984, Rhyacophila ligurica Oláh & Vinçon 2021, Rhyacophila harmasa Oláh & Vinçon 2021 and Rhyacophila abruzzica Oláh & Vinçon 2021. However, R. lignumvallis differs in the shape of the X tergum, 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 appendage.

The dorsal surface of the X segment is convex in all these species but narrower and taller in R. lignumvallis, R. tsurakiana, and R. harmasa. However, in dorsal view, R. lignumvallis has a slightly membranous, mesal-notched, and bulging X segment, whereas the X segment in R. tsurakiana appears flatter. In addition, the dorsal branch of the X tergum is rounded and wider in R. lignumvallis, whereas it is narrower in R. tsurakiana and R. harmasa.

The dorsal appendage of the phallic apparatus in R. lignumvallis is longer than the aedeagus and its parameres. This is also the case in R. harmasa, R. ligurica, R. pubescens, and R. tsurakiana but not in R. abruzzica. However, the shape of the dorsal appendage 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 protuberance on the mesal part of its dorsal surface, and R. tsurakiana has a straight and flat dorsal appendage.

In R. abruzzica, the dorsal appendix is broad and widens medially in lateral view. Compared with R. lignumvallis, R. tsurakiana, and R. abruzzica, the dorsal appendage 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 appendage is straight and rounded apically in R. lignumvallis, slightly inflated apically and rounded apically in R. harmasa, nearly straight and truncated apically in R. ligurica, tapering basally and truncated apically in R. tsurakiana, and rectangular in R. abruzzica.

The aedeagus and parameres of R. lignumvallis are most similar to those of R. pubescens. However, in lateral view, the tip of the aedeagus in the new species is more slender and slightly more curved apically than that of R. pubescens. In lateral view, the parameres of the new species are broader than those of R. pubescens. In ventral view, the parameres of the new species are club-shaped and curved, whereas in R. pubescens, the parameres are digitate and directed posterad. The second segment of the inferior appendix in the new species is triangular, with a straight dorsal margin, whereas all other species have a concave dorsal margin.

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”. 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 with crossveins connecting costal (C) and subcostal (Sc) veins; subcostal (Sc) and first radial (R1) veins, first (R1) and second radial (R2) veins (r), fifth radial (R5) and first medial (M) veins (r-m), first medial (M) and first cubital (Cu1) veins (m-cu), and first cubital (Cu1) and second cubital (Cu2) veins. Hind wing with crossveins connecting subcostal (Sc) and first radial (R1) veins, fifth radial (R5) and first medial (M) veins (r-m), and M3+4 and first cubital (Cu1) present.

Male genitalia. Segment IX longitudinally short in lateral view, 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. 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 rectangular in lateral view, slightly broader basally than apically; in ventral view, slightly broader apically than basally, with a small setose bump basally on mesal surface. Second article of inferior appendages quadrangular in lateral view, dorsal and ventral margins slightly diverging, posterodorsal margin straight, at a 130° angle to dorsal margin; in ventral view, mitton-shaped, mesal margin with very short, peg-like setae basally and longer setae apically. Phallic apparatus 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 broader than aedeagus, slightly curved posterodorsad, ventral margin straight, dorsal margin slightly sinuous, rounded apically; in ventral view, club-shaped, directed mesad. Aedeagus in lateral view slender, slightly sinuous, tapering towards its apex; in ventral view, slender and straight.

Original research

Rázuri-Gonzales E, Graf W, Heckenhauer J, Schneider JV, Pauls SU (2024). A new species of Rhyacophila Pictet, 1834 (Trichoptera, Rhyacophilidae) from Corsica with the genomic characterization of the holotype. ZooKeys 1218: 295-314, DOI:10.3897/zookeys.1218.132275

Dlium theDlium