Neoperla yentu Cao & Bae

Cao, Thi Kim Thu, Ham, Soon Ah & Bae, Yeon Jae, 2007, Description of three new species of Neoperla (Plecoptera: Perlidae) and a historical review of tropical Southeast Asian Perlidae, Zootaxa 1453, pp. 41-54 : 45-49

Neoperla yentu Cao & Bae sp. nov.

( Figs. 16–31 )

Description. Male body length 14.6 mm; antennae 10.1 mm; forewings 15.3 mm; hindwings 13.5 mm. General body color light brown with darker brown markings.

Head ( Fig. 16 ) light brown, with dark triangle on frons anterior to M–line, with large dark brown area from M–line to occiput and extending to compound eyes. Ocelli two, relatively small, located between compound eyes. Antennae dark brown. Maxillary and labial palpi dark brown.

Pronotum pale brown, slightly rugose, anteriorly slightly wider; anterolateral margin round. Mesonotum and metanotum pale brown. Wings ( Figs. 17, 18 ) hyaline; veins brown. Forewing Rs with 5 branches; C–Sc with 18 crossveins. Hindwing 3A forked. Legs relatively long; coxae and proximal femora yellow; tibiae, tarsi, and distal half of femora dark brown.

Abdominal tergum VII ( Fig. 19 ) weakly sclerotized, posteriorly with broad and round expansion covered with spinules; tergum VIII ( Fig. 19 ) with triangular sclerotized process possessing spinules at its apex; tergum IX covered with hairs. Hemiterga ( Fig. 19 ) hairy, weakly sclerotized, divided into three lobes; anterior, fingerlike lobe short and curved at tip; median lobes truncate and nearly meeting; posterior lobes as long as anterior lobes, acutely hooked distally. Sterna unmodified. Aedeagus tube ( Figs. 21, 22 ) ca. 2.3 mm long (length 5– 6 x width), entirely sclerotized. In lateral view ( Fig. 21 ), inner sac (not everted) relatively long and narrow; tube distally with tiny conical spinules. In ventral view ( Fig. 22 ), bulb swollen and darker, with paired lobes ( Fig. 22 ), with a pair of lobes ventrodistally. Cerci brown (cerci terminally broken).

Female body length 16.6–17.4 mm; antennae 10.7–11.2 mm; forewings 17.6–18.4 mm; hindwings 14.5– 15.8 mm. General morphology similar to male. Subgenital plate ( Fig. 20 ) strongly sclerotized posteromedially, emarginate, with lobes projecting posteriorly. Vagina sac–shaped ( Fig. 23 ) and membranous, anterolaterally with numerous concentric folds, raised medially with two wide, sclerotized, folded lobes separated by a median line; lobes covered with conical spinules. Spermathecal stalk and receptacle membranous.

Nymph. Body length 10.0–11.0 mm; antennae 9.4–10.6 mm; cerci 9.5–10.5 mm. Body ( Fig. 25) ground color pale yellow with darker brown markings. Head relatively flat, with wide dark brown band on anterior dorsal head; ocellar area and occiput not pigmented. Compound eyes relatively large, black, and with dense fringe of small bristles posteriorly. Antennae nearly as long as body, slender, light brown; basal two segments lighter in color.

Mouthparts pale brown. Labrum ( Fig. 26 ) width ca. 3x length; anterior margin fringed with fine hairs. Labial ( Fig. 27 ) paraglossae large and round, with fringe of fine marginal hairs; glossae reduced to proximal paraglossae; labial palpi slender, 3-segmented; palpal segments nearly equal in length; submentum very large, wider than long, anterior corners round; mentum reduced to narrow band. Hypopharynx triangular, with round hairly frontal margin. Mandibles ( Figs. 28–29 ) with two rows of bristles, with 5-6 teeth. Maxillae ( Figs. 30– 31 ) with strongly developed lacinial tooth, with a large moveable tooth followed by fringe of long bristles; maxillary palpi 5-segmented; segments 3 and 4 longer than other segments.

Pronotum ( Fig. 25) subquadrate, dark brown, with large pale areas medially; lateral margins incompletely fringed. Mesonotum and metanotum nearly similar in size, yellow-brown, with various darker markings. Thoracic gill tufts consisting of nine pairs: two on posterior supracoxal prosternum (PSC1, sensu Stewart & Stark 2002), two on posterior supracoxal mesosternum (PSC2), two on posterior thoracic abdomen (MTA), one on posterior supracoxal metasternum (PSC3), one on anterior thoracic mesosternum (AT2), and one on anterior thoracic metasternum (AT3). Legs relatively long, somewhat flattened; femora fringed with stout brown setae on both anterior and posterior regions (medially bare), with row of long white hairs along posterior margin; tibiae relatively long, slender, fringed with dense white hairs along outer margin.

Abdomen cylindrical, fringed with row of brown stout setae along posterior margin. Subanal lobe cylindrical, with pair of gill tufts terminally. Cerci nearly as long as body, dark brown.

Egg. Egg ( Fig. 24 ) oval, ca. 0.30 mm long and 0.21 mm wide; both poles similar. Collar and anchor absent. Chorion completely thin and seemingly smooth. Micropyles in upper third; orifices sessile.

Type material. Holotype: ɗ (SWU–PLE–23, reared, aedeagus dissected), Vietnam, Quang Ninh Prov., Yen Tu, 2.iii.2002, Thi Kim Thu Cao [SWU–AIC]. Paratypes: 2 ɗ (SWU–PLE–24, reared, 1 aedeagus dissected), 3 Ψ (SWU–PLE–26, reared, 1 vagina dissected) & 30 nymphs (SWU–PLE–25), same data as holotype [SWU–AIC]; 2 ɗ, Vinh Phuc Prov., Tam Dao NP, 16.v.1995, by light trap, Van Quang Nguyen.

Etymology. The specific name, yentu (noun), refers to the holotype locality of this species.

Diagnosis. Neoperla yentu sp. nov. belongs to the lushana – subgroup of the montivaga– group, which is widespread in Asia. The male adult of N. yentu is similar to N. diehli Sivec (in Zwick & Sivec 1985) in terms of the shape of the abdominal tergum VII and the shape of aedeagus, but can be distinguished by the absence of a darkened area in front of the subquadrate area in the abdominal tergum VII ( Fig.19 ) and by the absence of the spinules in two processes of the lobes of the aedeagus tube ( Fig. 21 ). The female adult can be distinguished by the central vaginal sac that has two widely sclerotized and folded lobes covered by several spinules ( Fig. 23 ). The nymph ( Fig. 25) can be distinguished from other described SE Asian Neoperla by the combination of the following characters: head markings, marginal dark brown groove in the pronotum, and anterolateral dark brown margins of both the mesonotum and metanotum.

Habitat and biology. Neoperla yentu is widely distributed throughout Vietnam. The adults and nymphs were found in mountain areas (alt. 450–970 m) where the streams were 5–20 m wide, canopied by trees. The coarse mineral substrate consisted of boulder (40%), cobble (30%), gravel and coarse sand (30%), and abundant fallen leaves. The adults were collected by light trap.

Distribution. Vietnam.

Figures

FIGURES 16 – 24. Neoperla yentu sp. nov. (16) Male head and pronotum. Scale bar = 0.5 mm. (17 & 18) Male right forewing and hindwing. Scale bar = 3 mm. (19) Male dorsal terminalia. Scale bar = 0.5 mm. (20) Female ventral terminalia. Scale bar = 0.5 mm. (21 & 22) Everted lateral and ventral aedeagus. Scale bar = 1 mm. (23 & 24) Female vagina and egg. Scale bar = 0.2 mm. M = micropyle.

FIGURES 26 – 31. Neoperla yentu sp. nov. nymphal mouthparts. (26) Labrum. Scale bar = 0.5 mm. (27) Labium. Scale bar = 1 mm. (28 & 29) Left and right mandibles. Scale bar = 0.5 mm. (30) Right maxilla. Scale bar = 1 mm. (31) Tip of right maxilla. Scale bar = 0.5 mm.