Compsoneuria langensis Braasch and Boonsoong

Braasch, Dietrich & Boonsoong, Boonsatien, 2010, A contribution to the Heptageniidae (Insecta, Ephemeroptera) of Thailand and Malaysia, Zootaxa 2610, pp. 1-26 : 7-11

Compsoneuria langensis Braasch and Boonsoong sp. nov.

Description. Male: Body length 8.42 mm; length of forewing 7.84 mm, length of hind wing 2.34 mm, length of caudal filaments 19.0 mm.

Head: Compound eyes grey, contiguous, speckled with few black spots (Fig. 19), thorax yellowish with brown middle streak.

Thorax: Forewing (Fig. 21) with first 6–7 cross veins of costal field thickened and brown shadowed; posterior cross veins mostly colourless or weakly brown; pterostigmal field milky white. Characteristic round, brown spot at the beginning of R1. A ‘cross band’ composed of about 9 brown cross veins down to hind margin in forewing; only a few tinged cross veins in the face of C, SC and R 1 in second half of wing; longitudinal veins colourless. Hind wing (Fig. 22) completely with brownish tinge; only 2 cross veins in subcostal field are brown tinted. Forewings have thickened cross veins brown shaded in costal and subcostal fields, crowded beneath second and third cross vein in C and SC fields; bulla region is expressed by a brown blotch; most other cross veins and all longitudinal veins are faintly brown or even colourless; first strong crossveins in costal fields are dark brown. Foreleg: femora length 2.0 mm, tibiae length 2.0, tarsi length 2.8 mm, lengths of tarsal segments in descending order: 3>2>4>1>5; midleg: femora length 2.8 mm, tibiae length 1.3 mm, tarsi length 0.9 mm, lengths of tarsal segments in descending order: 1>2>5>3>4; hind leg: femora length 1.8 mm, tibiae length 1.7 mm, tarsi length 1.1 mm, lengths of tarsal segments in descending order: 1>2>5>3>4; femur bands (Figs. 23–25) dorsally more or less with stippled patching, midband relatively distinct, but ventrally 3 bands clearly visible; 3 dark-brown bands on yellow ground in tibia, tarsal segments darkened distally. Cross bars are indicated by black streaks, other face of dorsal femur is speckled; tibia with 3 cross bars, ends of tarsal segments darkened.

Abdomen: Abdominal segments dorsally with marks as in Fig. 27; ventrally with pattern as in Fig. 26. Genital segment of male ventrally with convex styliger, at the sides slightly elevated to low forceps sockets (Fig. 28); forcipes 3.6 mm with proportion of segments like 0.4: 2.3: 0.5: 0.4, slightly curved, segments with exception of darker basal one grey-white; penis stocky, stem on its length almost evenly (Figs. 29–30).

Description. Female: Body length 7.0 mm, length of forewing 8.1 mm, length of hind wing 1.98 mm, length of caudal filaments 15.4 mm.

PLATE IV. FIGURES 19–30. Imagos of Compsoneuria langensis sp. nov. 19, Male head, dorsal view. 20, Female head, dorsal view. 21, Male forewing. 22, Male hindwing. 23, Male foreleg. 24, Male middle leg. 25, Male hindleg. 26, Female, terminal part of sterna. 27, Male, abdominal tergum, color pattern. 28, Male genitalia, ventral view. 29, Penis, ventral view. 30, Penis, dorsal view.

PLATE V. FIGURES 31–36. Larva of Compsoneuria langensis sp. nov. 31, Head capsule. 32, Labrum, dorsal view (left) and ventral view (right). 33, Right mandible. 34, Left maxilla, ventral view. 35, Hypopharynx, dorsal view (left) and ventral view (right). 36, Labium, dorsal view (left) and ventral view (right).

Head: light with distinctive brown pattern (Fig. 20); distance between eyes 6x of median ocellus width.

Thorax: Forewings with blackish first cross vein and brown longitudinal veins; cross veins strongly brown shaded; hind wing with weakly shaded cross veins in costal field. Fore- and midlegs lost, hind femora length 1.98 mm, hind tibiae length 1.1 mm, tarsi length 0.9 mm; lengths of tarsal segments in descending order: 1>2>5>3>4; hind femur speckled, femur bands visible, cross band of tibia in first third, second cross band between half and second third; ends of tibia and tarsal segments darkened.

Abdomen: Light brown with median blackish brown marks similar as in male, parallel darker brown stripes on terga more extended than in male; on tergum VI middle mark in lightened field; terga VIII–IX almost brown with blurred marks, last tergum with 3 patches; sterna (Fig. 26) with more faint pattern, anal plate obtusely triangular, apex weakly notched.

Description.? La, male (unreared): Body length 6.0 mm, caudal filaments 7.5 mm.

Head: Subrectangular, anteriorly and laterally rounded, with concave hind margin; design consisting of 6 light spots around front margin in anterior half of head and some clear pattern between eyes and ocelli (Fig. 31); antennae shortly exceeding head margin laterally. Labrum: greatly expanded laterally; anterior area with dense long hairlike setae (Fig. 32). Mandibles: each with outer incisor longer than inner incisor, serrate; prosthecae consisting of tufts of 4–5 long setae; apical margin between incisor and molar areas with setae, lateral margin setaceous (Fig. 33). Maxillae: with long hairlike setae on inner margin and scattered hairlike setae on ventral surface; basal segment of maxillary palp with rows of hairlike setae on inner and outer margins, apical segment pointed, with rows of hairlike setae on outer margin (Fig. 34). Hypopharynx: with lingua convex at apex, each superlingua with lateral, somewhat recurved arm developed (Fig. 35). Labium: having U-shaped separation between glossae; paraglossae moderately expanded laterally (Fig. 36).

PLATE VI. FIGURES 37–45. Larva of Compsoneuria langensis sp. nov. 37, Foreleg, left, dorsal view. 38, Foreleg femur, bristles on dorsal face. 39, Foreleg, tarsal claw. 40, Abdominal terga I–X. 41, Whorls of spines of caudal filaments. 42, Gill I. 43, Gill III. 44, Gill V. 45, Gill VII.

Thorax: Darker brown; femora of forelegs with dark brown marks as in Fig. 37, posterior margin with fringe of long setae, with both acute spines on surface distally rounded (Fig. 38). Mid- and hind legs similar to forelegs. Claws each with 3 small subapical denticles (Fig. 39).

Abdomen: Terga (Fig. 40) yellowish with a distinctive brown pattern of oblong stripes and blotches; posterolateral spines less developed. Gill set is represented by gill I, III, V and VII (Figs. 42–45). Caudal filaments with whorls of small spines and narrow black to brown segments alternately (Fig. 41).

Etymology: The name refers to the Nam Lang River, where the species has been found.

Diagnosis: The new species is recognized by large brown patches in male forewings (Fig. 21) and by completely brown-tinged hind wings (Fig. 22); in both sexes contrasting with other Compsoneuria Eaton, 1881 species with merely cross veins brown shaded. The only species in having brownish-tinged hind wings is, according to Webb et al. (2006), the Javan Compsoneuria lieftincki ( Ulmer, 1939) . However, apart from other penial characters ( Ulmer 1939: Fig. 164), legs are quite different due to four dark cross bars in each femur and lacking cross bars on the tibiae. The speckled patterns of head, body and legs in adults and larvae are very characteristic for genus Compsoneuria Eaton, 1881 ( Braasch & Soldán 1986b; Sartori & Elouard 1996; Ulmer 1939), but difficult to use for separating species, because they are relatively similar among species but rather variable within species. Fortunately, the species are readily distinguished by differences in gill shape of full-grown larvae.

Biology: Besides Compsoneuria langensis , a few male specimens of C. thienemanni ( Ulmer, 1939) were found in the mountainous region of Soppong in 2001–2005. However, the latter species, although very abundant, was the only species in the larger rivers of lower altitudes, namely Mae Nam Ping and Mae Nam Chaem near Hot, Chiang Mai Province, in IV 2003, alt. ca 200 m, 18°12’07.54’’ N, 98°36’32.85’’ E. Both species are mainly found at floating water plants or even thick pads of green algae.

Material examined: HOLOTYPE: male, Thailand, Mae Hong Son Province, Soppong, Nam Lang River, 19°34.447´N, 98°16.727´E, alt. 605 m; 03.–25.IV.03, at light (DB); PARATYPES: 11 males, 17 females, same locality, same time, at light (DB).

Further material: 4 La, Soppong, Nam Lang, 03.–25.IV.03, botton sample (DB); 1 La, Nam Lang, 10 km below Soppong, same time, bottom sample (DB); 1 La, same region, Nam Khom River 19°21’N, 97°57’E, alt. ca 600 m, 08.IV.03, bottom sample (DB); 3 La, same region, near village Mena, right tributary of Mae Nam Pai River 19°26’N, 98°23’E, alt. ca 622 m; 25.IV.03, bottom sample (DB); 5 La, same region, Mae Nam Pai River, near village Pai 19°22’N, 98°26’E, alt. ca 622 m; 25.IV.03, bottom samples (DB).

Types deposition: HOLOTYPE: male ( MNHU, 70% alcohol); PARATYPES: 1 male, 1 female ( MNHU); 2 males, 1 female ( SMF Eph), 2 males, 2 females ( ZMKU); males, females (DBP); some presumed La of species in collections as above.