Sialis primitivus, Liu, Xingyue, Hayashi, Fumio & Yang, Ding, 2015

Liu, Xingyue, Hayashi, Fumio & Yang, Ding, 2015, Sialis primitivus sp. nov. (Megaloptera: Sialidae), a remarkable new alderfly species from China, Zootaxa 4033 (4), pp. 593-599 : 594-597

Sialis primitivus sp. nov.

( Figs. 1–11 )

Description. Male. Body length 5.9–7.7 mm; forewing length 8.7–10.4 mm, hindwing length 8.2–9.2 mm.

Head ( Figs. 1, 3 ) smoothly orange, pale brown on clypeus, with dense short yellowish pilosity dorsally and a few brown setae laterally; raised scars indistinct. Compound eyes brown. Antennae blackish brown, with scape and pedicel yellowish brown. Mouthparts pale brown, with maxillary and labial palpi blackish brown; labrum ( Fig. 4 ) with a U-shaped median notch; mandibles with two small teeth posterior to terminal tooth and a tiny tooth anterior to terminal tooth, and distally with a feebly developed inner fossa ( Fig. 4 ).

Prothorax ( Figs. 1, 3 ) orange, pronotum with anterior margin reddish brown; meso- and metathorax yellowish brown. Legs yellowish brown, bearing dense brownish setae, with tibiae and tarsi blackish brown; tarsal claws auratus. Wings ( Fig. 1 ) pale blackish brown, slightly darker on costal areas and proximal portions; veins brown. Forewing about 3.0 times as long as wide, with 6–7 distinct costal crossveins (remaining distal ones almost reduced); sc-r present; Rs with two simple branches; MA with two simple branches, MP with simple anterior branch and bifurcate posterior branch; CuA bifurcated; three crossveins present between R and Rs. Hindwing about 3.0 times as long as wide; venations similar to that of forewing, with 3–4 distinct costal crossveins (remaining distal ones almost reduced).

Abdomen blackish brown. Tergite 9 ( Fig. 6 ) in dorsal view nearly 3.0 times as wide as long, anterior margin broadly and arcuately concaved, posterior margin nearly truncate. Sternite 9 ( Fig. 7 ) short, about 3.0 times as wide as long, posterior margin arcuately convexed. Gonocoxites 9 ( Figs. 6–9 ) widely apart from each other, each gonocoxite directed posterodorsad, anteriorly feebly sclerotized, posterior portion setose, subtriangular in ventral view and ovoid in caudal view. Ectoproct ( Figs. 6–9 ) present as a short, ring–like structure, directed posteroventrad, with dorsal and ventral ends almost touching but not tightly fused with each other. Fused gonocoxites 11 ( Figs. 7–9 ) proximally with a pair of broad foliate lobes, distally with a pair of median processes (= gonostyli 11), which are simply claw-like and directed posteroventrad.

Female. Body length 7.9–8.4 mm; forewing length 9.7–11.6 mm, hindwing length 8.9–10.0 mm.

Labrum ( Fig. 5 ) with a small V-shaped median notch; mandibles ( Fig. 5 ) with three small teeth posterior to terminal tooth.

Sternite 7 ( Figs. 10–11 ) broad, subtrapezoidal in lateral view and broadly lingulate in ventral view, with posterior margin arcuately convexed. Fused gonocoxites 8 ( Figs. 10–11 ) rather short, much narrower than sternite 7, medially strongly narrowed, forming a pair of ovoid lateral parts, a small genital hole present at middle; gonapophysis 8 ( Figs. 10–11 ) feebly sclerotized and distinctly convex posteriad. Gonocoxite 9 ( Fig. 10 ) broadly valvate, arcuately margined ventrad, posteriorly with a small gonostylus 9 at tip. Ectoprocts ( Fig. 10 ) short, ovoid.

Type materials. Holotype ♂, “ China, W[est]. Hupeh [= Hubei Province], Lichuan Distr[ict]., Suisapa [= Shuishanba Village, 30°05′N, 108°37′E], 1000 m, VII-31 -[19]48/Collectors Gressitt & Djou” ( CASC). Paratypes: 9♂ 10♀, same data as holotype, 31.VII.1948 ( CASC); 1♂, same data as holotype, 30.VII.1948 ( CASC); 4♂ 3♀, same data as holotype, 26.VII.1948 ( CASC); 1♀, same data as holotype, 29.VII.1948 ( CASC); 1♀, same data as holotype, VII.1948 ( CASC); 1♂, same data as holotype, 6.VIII.1948 ( CASC); 1♂, same data as holotype, 8.VIII.1948 ( CASC).

Distribution. China (Hubei).

Etymology. The specific epithet “ primitivus ” refers to the putative basalmost position of the new species in Sialis .

Remarks. The new species can be easily distinguished from all other Sialis species by the orange head and prothorax and by the Rs with only two branches. In all other known species of Sialis , the Rs has three to five branches, and there is only one species, i.e. S. versicoloris Liu & Yang, 2006 , in which the female has orange head and prothorax, but the head of conspecific male is entirely black ( Liu & Yang 2006a). Notably, the orange head and prothorax as well as the wing venation features (i.e. Rs 2-branched and MP with simple anterior branch and bifurcated posterior branch) are shared by the Madagascan endemic genus Haplosialis Navás, 1927 and some species of the American endemic genera Protosialis and Ilyobius ( Liu et al. 2015a). However, S. primitivus possesses an important synapomorphy of Sialis , the inner fossae on male mandibles ( Liu et al. 2015a), which indicates that this new species is a member of Sialis .

All examined specimens of the new species were collected from western Hubei Province of central China during a joint expedition called “The California Academy-Lingnan Dawn-Redwood Expedition” in 1948 (see the description of this expedition in Gressitt (1953)). The collecting site “Suisapa [= Shuishanba Village]” is wellknown with the largest natural population of Metasequoia glyptostroboides Hu & Cheng (dawn redwood), one of three species of conifers known as redwoods and considered to be a “living fossil” since its congeneric relatives are fossil taxa from the Late Cretaceous to Miocene in the Northern Hemisphere.

Figures

FIGURES 1 – 5. Sialis primitivus sp. nov. 1. Habitus, holotype male; 2. Habitus, paratype female; 3. Head and pronotum, male; 4. Mandibles and labrum, male; 5. Mandibles and labrum, female. Arrow indicates the inner fossa of male mandible. Scale bars = 0.5 mm (Figs. 3 – 5) and 2.0 mm (Figs. 1 – 2).

FIGURES 6 – 9. Sialis primitivus sp. nov., male. 6. Genitalia, dorsal view; 7. Genitalia, ventral view; 8. Genitalia, lateral view; 9. Genitalia, caudal view. e: ectoproct; gx: gonocoxite; gst: gonostylus; T: tergite; S: sternite. Scale bars: 0.5 mm.

FIGURES 10 – 11. Sialis primitivus sp. nov., female. 10. Genitalia, lateral view; 11. Genitalia, ventral view. bc: bursa copulatrix; e: ectoproct; gx: gonocoxite; gst: gonostylus; gp: gonapophysis; T: tergite; S: sternite. Scale bars: 1.0 mm.