Forewing length 11 mm. Wings yellowish with vigorous dark venation.

Head dark brown; lateral occipital spots light brown; antennae dark brown and approximately as long as the body; palpi pale with dark margins.

Cervical gills long and slender, without apical constrictions.

Pronotum slightly lighter than head; with dark rounded markings; anterior margin dark; lateral margins light brown; quadrangular-shaped with sharp rectangular corners; anterior margin slightly broader than posterior one.

Legs generally yellowish; colouration similar at fore-, mid- and hindlegs; femora yellowish with narrow dark bands at distal ends; tibiae covered with short dark bristles; tarsi dark brown.

Abdominal segments 1-7 middle brown; segments 8-10 dark brown; pronounced pilosity on segments 8-10.

Tergum VIII dark brown, with several dark short posteriomedial spines. Tergum IX sclerotised, with a posteriomedial membranous indentation in between two lobe-like sclerotised structures, bearing several short, black spines. Tergum X sclerotised, except for a wide medial membranous depression bearing several anterolateral spines (Fig. 1b).

Male terminalia (Fig. 1): Hypoproct basally subrectangular; about half the width of sternite IX; longer than wide; with parallel lateral margins; distally extended into a short, blunt process.

Vesicle claviform; more than two times longer than wide.

Paraprocts trilobed. Inner lobe much shorter than median and outer lobes; distally expanding before ending in an elongated, slender apex. Median lobe with wide, rounded base; basal sclerotised structure triangular-shaped with a distinctly pointed apex; prolonged in a pronounced and darkly sclerotised, inwards-orientated inner expansion with several spines at the distal end and a membranous apex covered with setae, approximately as long as the ridge-like inner expansion. Outer lobe in ventral view boot-shaped; widely enlarged at the tip; bearing a strong, inwards-curved spine.

Cerci conical; short; covered with setae; tip blunt, with a small nipple-like structure (Fig. 1a).

Epiproct with parallel margins, narrowing towards the apex. Terminating in a blunt, rounded tip, which is prolonged by a bilobed, membranous extension. Terminal filament rather short and bifid. In lateral view, the filament extends in the same axis as the epiproct (Fig. 1e, f). Length of ventral sclerite two-thirds of the epiproct; apical end with numerous, prominent spines. Dorsal sclerite in dorsal view with a strongly sclerotised, straight base. Lateral branches as long as the epiproct; ending in two slender, inwards-curved tips. Female and larva: unknown.

Protonemura eclipsis sp. nov. is distinguished from congeners by the distinct form of the inner, median and outer lobes of the paraprocts, as well as by the shape of the epiproct.

Eclipsis is derived from the Greek root word ékleipsis, respectively the Latin root word eclipsis. In English, the term eclipse typically refers to the partial or complete obscuring of one celestial body by another or by the shadow of another, but is also associated with a broader range of meanings like darkness, obscurity or blackness. The specific name is a tribute to Pink Floyds song “Eclipse” and refers to the dark and prominent appearance of the paraprocts.

The presence of a bifid terminal filament at the apex of the epiproct designates the new species as a member of the Protonemura corsicana species group, P. corsicana subgroup (Vinçon and Murányi 2009). Protonemura eclipsis sp. nov. is morphologically closely related to Protonemura albanica; however, it differs from P. albanica mainly by the shape of the paraprocts (Raušer 1963, fig. 2; Murányi 2007, figs. 79–82). While the outer lobe of the paraprocts bears two spikes on the outer projection in P. albanica (Fig. 2b), the outer lobe of the new species is missing such a structure (Fig. 2a). The shape of the median lobe is rounded in P. albanica, but is pointed and, thus, triangular-shaped in the new species. The inner expansion of the median lobe is slim and convex in P. albanica (Murányi 2007, figs. 79–82), while the new species bears a much more pronounced, ridge-like and concave structure with a variable number of prominent spines at the distal end. Furthermore, the distal endings of the lateral branches of the dorsal sclerite of the epiproct are straight in P. albanica, while they are pointed inwards in the new species (Fig. 2c, d). In lateral view, the lower ridge of the epiproct of P. albanica bears a hemispherical bulge with numerous spines (Raušer 1963, fig. 2F). In the new species, however, the spines insert directly on the inferior face of the epiproct, a hemispherical bulge is missing.

According to the previously mentioned characteristics of the four subgroups of the P. corsicana group (Vinçon and Murányi 2009), we propose to place the new species in the P. corsicana subgroup. The placement in the P. corsicana subgroup is not only justified by the considerable morphological similarities between P. eclipsis sp. nov. and P. albanica, but also by the shape of the ventral bulge of the epiproct. As opposed to a strongly pronounced ventral bulge in the three other subgroups, members of the P. corsicana subgroup are characterised by a slight ventral bulge of the epiproct, which also applies for the new species.

The new species differs from Protonemura miatchense Ikonomov, 1983 by the shape of the paraprocts (Ikonomov 1983, figs. 18–22). While the inner lobe is slim and outwards-orientated in P. miatchense, the inner lobe of the new species is distally expanding before ending in an elongated, slender apex. Furthermore, the inner expansion of the median lobe is slim and single-pointed in P. miatchense, while the corresponding structure of the new species bears a variable number of prominent spines at the distal end. The terminal filament of the epiproct is much shorter in Protonemura miatchense than in the new species.