Neoperlops vietnamellus, Cao & Bae & Vii-Ix, 2008

Cao, Thi Kim Thu, Bae, Yeon Jae & Vii-Ix, N., 2008, Neoperlops vietnamellus, a rare stonefly from Vietnam (Plecoptera: Perlidae), Zootaxa 1968, pp. 33-38 : 34-37

Neoperlops vietnamellus , sp. nov.

( Figs. 1–19)

Diagnosis. The male adult of this species is distinguished by the unique distribution of patches of sensilla basiconica posteromesally on the abdominal terga VII–IX, by the absence of sensilla basiconica on the anterior processes of the hemiterga, by the absence of prominent spines along ventral edge of the hemiterga, and by the aedeagus being completely covered by fish-like scales. In the female, the subgenital plate is a well sclerotized, slightly protruding, mesal tab. The nymphs have a distinct light M-line marking on the head, while the egg chorion is completely smooth.

Description. Male adult. Body length 19.6 mm; antennae 17.8 mm; forewings 22.1 mm; hindwings 20.2 mm. General body color pale brown with dark brown markings. Head ( Fig. 1) pale brown, slightly wider than pronotum, with dark brown markings from ocelli and forward to center of head and posterior to occipital ridge areas. Ocelli two, small, adjacent to tentorial callosities. Tentorial callosities slender, rod-shaped. Antennae generally pale brown, darker toward tip. Pronotum ( Fig. 1) elongate oval; corners rounded; surface with faint rugosities. Wings ( Figs. 2–3) pale, veins brown. Forewing Rs with 5 branches; C - Sc with 22 crossveins. Hindwing 3A forked. Legs relatively long; apex of femora, base of tibiae and tarsi dark brown. Anterior metasternum and abdominal sterna IV–VII with brush of brown hairs medially (hair brush poorly developed on abdominal sternum IV). Abdominal terga VII–IX ( Figs. 4–5) with patches of sensilla basiconica posteromedially (patches of sensilla basiconica denser on terga VIII–IX). Hemiterga anterior processes ( Fig. 5) finger-like, slightly curved anteriorly, and slightly exceeding posterior margin of abdominal tergum IX; tip round, without sensilla basiconica; inner part slightly swollen, forming basal callus-like structure covered with several sensilla basiconica marginally. Cerci brown, relatively long, ca. 0.5 x length of body. Penis tube ( Figs. 6–7) relatively short, ca. 0.7 mm in length, covered with fish scale-like spinules; everted sac shorter than tube length (ca. 0.4 mm), mostly covered with fine spinules (spinules denser in number in dorsoapical area), with unarmed triangular basal process.

Female adult. Body length 21.7–23.0 mm; antennae 17.8–19.3 mm; forewings 25.0– 26.8 mm; hindwings 23.8–25.3 mm. General color similar to male; body larger than male. Abdominal sterna I–VII with membranous folds. Abdominal sternum VIII ( Figs. 8–9) with slightly protruding subgenital plate as a strongly sclerotized mesal tab. Vagina ( Fig. 10) membranous, subquadrate. Spermathecal stalk slender, longer than vagina length; spermatheca large bulbous, with a single accessory gland.

Nymph. Body length 9.6–19.6 mm. General body ( Fig. 12) color pale to dark brown. Head slightly wider than pronotum (head width 2.8–5.0 mm), with light M-line marking, and with light markings on clypeus and behind ocelli. Occipital ridge straight, with complete fringe of short brown setae. Compound eyes large, black, and elongated. Ocelli two, small. Antennae brown, relatively long, nearly as long as body length (7.6–17.5 mm in length). Mouthparts brown. Labrum ( Fig. 13) dorsally covered with black hairs, ca. 4.0 x wider than long; anterior margin convex, fringed with white silky hairs. Labium ( Fig. 14) with well developed and round paraglossae; glossae greatly reduced; submentum very large, wider than long, with round margin; mentum reduced to narrow band; labial palp slender, 3-segmented (segments nearly equal in length). Hypopharynx triangular; anterior margin round and cover with patch of strong brown hairs. Mandibles ( Figs.15–16) with two rows of setae on inner margin; right mandible with six teeth and left mandible with five teeth. Maxillae ( Figs.17–18) well developed; lacinia long and slender, sharply pointed at tip with a large strong moveable tooth on interior side, followed by a fringe of stout setae; galea ( Fig. 19) shorter than lacinia, with few strong setae near tip; maxillary palp long and slender, 5-segmented (segments 1–4 subequal in length, segment 5 small). Pronotum quadrate, wider than long, brown, with symmetrical yellow markings, with marginal groove dark brown, and with incomplete fringe of thick setae along lateral margin; all nota with median longitudinal row of long silky hairs. Legs relatively long, somewhat flattened; posterior margin with row of dense white hairs; tarsal claws sharp, prominent, and with a small basal spur. Abdomen cylindrical, covered with black hairs, and with row of long median silky hairs; abdominal terga with fringe of stout setae on posterior margin; abdominal sternum VII with complete posterior fringe. Paraproct lobes small, with a pair of gill tufts. Cerci long, nearly as long as body length (cerci length 7.1–18.5 mm), brown, without swimming hairs.

Egg. Egg ( Fig. 11) elongate oval, with short wide collar, ca. 0.37 mm long and 0.28 mm wide. Chorion surface completely smooth. Anchor short, attached with a number of long filaments. Micropyles not observed.

Type material examined. Holotype: Male adult (SWU-PLE-58, reared), Cat Cat (22°21'19" N, 103°54'28" E), alt. 1400 m, Sa Pa , Lao Cai Prov., Northern Vietnam, 23.iv.2002, DHH & VVN [SWU-AIC] . Paratypes: 2 male adults (SWU-PLE-59, 60, reared), Tam Dao NP (21°27'03" N, 105°38'27" E), alt. 700 m, Vinh Phuc Prov., Northern Vietnam, 16.iv.2002, DHH & VVN [SWU-AIC] ; 1 female adult (SWU-PLE-61, reared), Tam Dao NP, alt. 700 m, Vinh Phuc Prov., Northern Vietnam, 15.iii.2002, TKTC [SWU-AIC] .

Other materials: 8 nymphs (SWU-PLE-141), Cat Cat, alt. 1400 m, Sa Pa , Lao Cai Prov., Northern Vietnam, 21.iii.2002, TKTC ; 9 nymphs (SWU-PLE-140), Cau May, Sa Pa, Lao Cai Prov., Northern Vietnam, 22.iii.2002, TKTC ; 1 female adult (SWU-PLE-214), Rao Mac, Huong Son, Ha Tinh Prov., Central Vietnam, 9.v.2004, TKTC ; 1 female adult (SWU-PLE-215), Xuan Son NP, Phu Tho Prov., Northern Vietnam, 15.ix.2004 , Truong Xuan Lam; 1 female adult (SWU-PLE-216), Tam Dao NP, alt. 700 m, Vinh Phuc Prov., Northern Vietnam, 2.vii.2003, TKTC .

Etymology. The specific epithet, vietnamellus , is a modified version of the word “ Vietnam ”.

Distribution. Northern and Central Vietnam.

Remarks. In the genera of the tribe Perlini , Neoperlops Banks appear to be closely related to the genus Tetropina Klapálek by their shared adult characters of the head tentorial callosities adjacent to the ocelli and the presence of hair brushes on the metathoracic and abdominal sterna ( Zwick 1984). Based on our close examination of Vietnamese material, these two genera differ in the arrangement of sensilla basiconica on the abdominal terga VII–IX and in the presence of inner basal callus-like structures on the hemiterga in Neoperlops , as is also the case in N. vietnamellus . Recently, Stark & Sivec (2008) discussed the differences in nymphs between Tetropina and the putative nymph of N. obscuripennis . Their presumed Neoperlops nymphs lacked a mid-dorsal row of long silky setae, had a complete, lateral pronotal fringe, and lacked intercalary bristles on the dorsal surface of abdominal terga. However, our reared nymphs of N. vietnamellus have a row of long median silky hairs dorsally on the abdomen and have an incomplete fringe of thick setae on the pronotum.

Adult males of Neoperlops vietnamellus are similar to N. gressitti and N. obscuripennis in general appearance. However, in N. vietnamellus the hemitergal processes lack the spines along the ventral edge, present in both N. gressitti and N. obscuripennis ( Zwick 1984, Stark & Sivec 2008). The apex of the hemitergite of N. vietnamellus is finger-like, whereas that of N. gressitti is conical and in N. obscuripennis it is spatula-shaped. The armature on the aedeagus of N. vietnamellus is mostly covered by fine fish-scale like spinules, while in both N. gressitti and N. obscuripennis , completely bare areas occur subapically on the dorsal surface and again apically, the subapical area containing one or two patches of spinules, respectively ( Zwick 1984, Sivec et al. 1988, Stark & Sivec 2008).