Darthus vadorus Webb & McCafferty, 2007

Webb, J. M. & Mccafferty, W. P., 2007, A new genus and species of Heptageniidae (Ephemeroptera) from Borneo, with revisions to the classification of the Ecdyonurinae, Zootaxa 1478 (1), pp. 41-48 : 46-47

Darthus vadorus Webb & McCafferty n. sp.

Larval description: Body length 6.5 – 8.5 mm; caudal filaments slightly longer than body. General color yellowish brown to brown.

Head: Head capsule brown with pale stripe from lateral ocelli to lateral margin and pale spot anterior of median ocellus; anterior margin slightly thickened and with row of fine setae (Fig. 2). Labrum (Fig. 3) 5X wider than long, dorsal surface with dense brush of highly fimbriate setae, ventral surface with anterior portion with dense, fine setae, and posterior portion with somewhat stouter setae. Mandibles as in Figs. 4 and 5. Hypopharynx (Fig. 6) expanded distolaterally, posterolateral corners rounded. Maxillae (Fig. 7) ventrally with scattered simple setae; apical margin with 20 comb setae and two simple setae; distal dentisetae branched near base; palps with numerous fine setae on first segment, second and third segments mostly fused, with dense brush of setae apically and with terminal spine. Labium as in Fig. 8; glossae subquadrate with numerous robust, bipectinate setae ventrally (Fig. 13); paraglossae ventrally with numerous robust, bipectinate setae apically, and dorsally with numerous long, fine setae.

Thorax: Forelegs yellowish brown; forefemora with regular row of long setae dorsally, anterior face with paddle-shaped setae and small spines, ventral margin with robust pointed setae; foretibae with row of long, fine setae and 22 long, clavate robust setae on lateral ridge, posterior margin with row of short, fine setae, anterior margin with two robust setae, inner surface with four simple, robust setae and scattered fine setae; foretarsi with dense row of long fine setae and 5 long robust setae, entire surface with scattered fine setae; claws with three denticles. Midlegs similar to hindlegs but with fewer setae. Hindlegs (Fig. 9) yellowish brown; hindcoxae with subquadrate dorsal extension; hindfemora with regular row of long setae dorsally, anterior face with paddle-shaped setae (Fig. 14) and small spines, ventral margin with robust pointed setae; hindtibiae with row of long, fine setae and 15–20 long, clavate robust setae on lateral ridge, row of long, fine setae on posterior margin, 4–10 short, robust setae on anterior margin, inner surface with seven simple, short, robust setae and scattered short, fine setae; hindtarsi with dense row of long, fine setae and two long, robust setae, inner surface with three robust setae, entire surface covered with short, fine setae; claws with three denticles.

Abdomen: Terga brown with slightly paler spots submedially and laterally, with median ridge present on 2–9 (Figs. 1, 12); sterna yellowish brown; small posterolateral spines present on segments 8 and 9; gills 1 with lamellae absent, fibrils well developed; gills 2–6 (Fig. 10) with lamellae long, slender, and curved, 12X longer than wide, outer margin with fringe of setae, fibrils well-developed; gills 7 (Fig. 11) with lamellae 3X longer than wide, anal margin with sharp serrations in basal half, outer margin with fringe of setae, fibrils absent. Caudal filaments brown, with small robust setae and short fine setae at articulations.

Egg: Slightly oval, 13 µm long, 8.75 µm wide (Fig. 15). Chorion with numerous KCTs and small tubercles. KCTs more numerous at poles, those at one pole larger. Micropyle slightly oval and with rim slightly thickened (Fig. 16).

Adult: Unknown.

Etymology: The specific epithet is an allusion to the given name of the fictional character Darth Vader.

Diagnosis and discussion: Because Darthus is monospecific, the specific diagnosis is the same as the generic diagnosis. Afronurus temburongensis Braasch and A. bruneiensis Braasch were recently described from Borneo from adult males (Braasch 2005). We do not believe either of these is the adult of D. vadorus because they are both light-colored species and the mature larva of D. vadorus has brown abdominal segments. We have seen a male of an undescribed species collected near the type locality of D. vardorus that may represent the adult of D. vadorus because it has brown abdominal segments and genitalia that are slightly different than those of other southeast Asian species of Afronurus . As this association cannot be verified at this time, we choose not to describe this specimen because much confusion has been created in the past by incorrectly associated larvae and adults, as discussed, for example, by Webb et al. (2006).

Material examined: HOLOTYPE: 1 larva, Indonesia, E Kalimantan, Kayan-Mentarang Nature Reserve, Nggeng R, 2°52' N, 115°49' E, 30-March-1994, coll. B Hubley and DC Darling ( ROM collecting event # IIS940510) [ MZB] . PARATYPES: 1 larva, Indonesia, East Kalimantan, Malinau basin, stream Wok (Sungai Guang), tributary of the Seturan River , 2°59'12'' N 116°33'11'' E, April 5, 2001, coll. P Derleth [ MZL] ; 13 larvae (parts of 2 slide-mounted in Euparal and cellosolve), same data as holotype [ PERC] ; 1 larva, Indonesia, E Kalimantan, Bulungan, Kayan-Mentarang Nature Reserve , Lalut Birai Res. Stn 20, 2°51' N, 115°48' E, Feb-4 March 1993, coll DC Darling ( ROM collecting event # IIS930003) [ ROM] .