Aphelocheirus bruneiensis, Zettel, Herbert, Lane, David J. W. & Moore, Stephen, 2008

Zettel, Herbert, Lane, David J. W. & Moore, Stephen, 2008, Aphelocheirus (s. str.) bruneiensis sp. n., a new benthic water bug (Hemiptera: Heteroptera: Aphelocheiridae) from Brunei, and a key to Bornean Aphelocheirus, Zootaxa 1920, pp. 61-68 : 62-66

Aphelocheirus (s.str.) bruneiensis sp.n.

( Figs. 1–10 )

Etymology. The Latinized adjective bruneiensis refers to the country of origin, Brunei.

Holotype (brachypterous male; Brunei Museum, Collection No. NHS/BM.INS. 01.20.08), paratype (macropterous male; Natural History Museum Vienna, Collection No. NAUC-187/1), and paratype (nymph, 4th or 5th instar; Universiti Brunei Darussalam, Collection No. UBDM.3.00005) labelled " Brunei Darussalam \ Sungai Tutong Survey\ site 17B, 15 June 2004 \ leg. Stephen Moore".

Type locality. Brunei Darussalam, Sungai Tutong at Rambai road bridge (4.629° N, 114.651° E); see also ecological description below.

Description of brachypterous male (holotype). Size. Body length 6.1 mm. Body width 4.0 mm. Pronotum width 3.3 mm.

Colour. Dorsal colour pattern see Figure 1 . Ventral side, including appendages, yellowish, partly brownish infuscated.

Head ( Fig. 1 ) moderately long, length 1.05 times head width; finely, uniformly punctured, distance between punctures mostly (except anteriorly) smaller than their diameter, medioposteriorly punctures confluent. Anterior section of head (anterior of anterior eye margin) short, 0.5 times eye length (eye length measured parallel with median line of head). Rostrum 1.7 times as long as profemur, tip reaching distal end of mesotrochanter.

Thorax: Pronotum ( Fig. 1 ) only slightly convex, medially finely coriaceous, laterally finely granulate. Median length of pronotum 0.6 times median head length. Maximum width at posterior corners, 2.75 times its median length. Lateral margins of pronotum strongly convex and convergent anteriorly; width at anterior corners 0.43 times maximum width. Propleuron ( Fig. 5 ) medially with very stout process, demarcated by almost rectangular incision. Mesosternum with extremely high median carina, ending abruptly anteriorly ( Fig. 5 ) and bearing some ill-defined wrinkles; in lateral view anterior corner almost rectangular (slightly acute). Mesoscutellum finely granulate; anterior width 2.5 times median length, its centre only slightly convex.

Hemielytra ( Fig. 1 ) delicately granulate, small, posteriorly not reaching posterior margin of tergite 2, medially with gap measuring 0.28 times hemielytron width. Each hemielytron slightly wider than long (ca. 1.1 times), laterally with prominent triangular embolium process (process width ca. 0.2 times total hemielytron width).

Legs relatively short and stout, femora laterally not much exceeding margin of body. Profemur longer than both meso- and metafemur; 2.8 times as long as wide.

Abdomen ( Fig. 1 ). Tergites 2–7 with acute posterior corners, but corners of tergite 2 very small. Sternites only slightly asymmetrical, without peg-like setae. Sternites 4–5 with very distinct, sharp median carina.

Genitalia: Pygophore ( Fig. 6 ) apically with short, roundish tubercle; left parandrium distinctly longer than right one, its apex hook-shaped and slender; right parandrium wide, its apex obliquely truncate. Both parameres stout and short, approximately 0.4 mm in length, scaly microstructures in distal part very delicate, distinct only under very high magnification. Left paramere ( Figs. 7, 8 ) broad, leaf-shaped, apically almost truncate, proximally with very prominent process, ventrally with three long setae, otherwise with short and inconspicuous pilosity. Right paramere ( Figs. 9, 10 ) broad sickle-shaped, medially with several longer setae, laterally with very short pilosity.

Description of macropterous male (paratype). Size. Body length 6.1 mm. Body width 3.9 mm. Pronotum width 3.2 mm.

As usual in Aphelocheirus , macropterous specimens are slightly darker than brachypterous individuals, with slightly coarser sculpturing of head, pronotum, and mesoscutellum, slightly larger eyes, a differently shaped pronotum, a strongly enlarged mesoscutellum, and forewings reaching approximately the tip of the abdomen (see Fig. 2 ).

Head ( Fig. 2 ) moderately long, length 1.25 times head width; uniformly punctured; anterior section of head short, 0.5 times eye length. Pronotum ( Fig. 2 ) slightly convex, with sinuate hind margin; median length of pronotum 0.75 times median head length; maximum width near posterior corners, 3.3 times its median length; width at anterior corners 0.44 times maximum width. Propleuron with medial process as in brachypterous morph. Mesosternum with similar median carina as in brachypterous morph, but posteriorly less highly raised above the more swollen mesosoma. Embolar margin of hemielytron strongly expanded laterally, forming a sharp wing-shaped process ( Fig. 2 ). Abdomen including genitalia as in brachypterous morph.

Description of nymph (paratype). Size. Body length 5.1 mm. Body width 3.6 mm. Pronotum width 2.8 mm.

Colour. Dorsal colour pattern see Figure 3 . Ventral side, including all appendages, pale yellowish. Dorsal surface partly smooth and shining but with delicate sculpturing; with distinct, short pilosity; median line of thorax and abdomen with more or less distinct carina. Head short, length 0.9 times head width; anterior section of head 0.5 times eye length. Pronotum ( Fig. 3 ) almost flat, maximum width at posterior corners 5.0 times its median length. Sides of pronotum strongly convex and convergent anteriorly; width at anterior corners 0.40 times maximum width. Propleuron medially simply rounded. Mesosternum with distinct median carina, ending abruptly anteriorly, although less high than in adults. Sternites 3–6 with very distinct, sharp median carina. Sternite 3 with two subapical setae (homologous with peg-like bristles?).

Female. Unknown.

Ecological description of type locality. Site 17 of the Sungai Tutong Survey 2004 ( Evans et al. 2005), i.e., the type locality of A. bruneiensis sp.n., is in the mid reaches of the river near Kampong Rambai, located 46 km upstream of the river mouth, below the Rambai road bridge ( Fig. 4 ). The site was unusual in that gabion baskets (used to stabilise the riverbed) created an artificially narrow, hard-bedded channel with moderate to fast flow. These habitat conditions differed from those of most of the length of the Sungai Tutong where slow-flowing, sandy-bedded, and grassy-margin habitats were predominant (in 23 of 25 sampling sites).

The Rambai bridge site supported aquatic invertebrates commonly associated with hard beds and moderate to fast currents, including hydropsychid caddisflies (37 % of the individuals found at this site), heptageniid mayflies (23 %), simuliid black flies (2 %), perlid stoneflies (2 %), and psephenid beetles (1 %). These groups were less commonly recorded in the sandy/grassy habitats found along most of the Sungai Tutong where the most common taxa included chironomid midges (subfamilies Chironominae and Tanypodinae ), baetid mayflies, libellulid dragonflies, and protoneurid damselflies.

The general water quality of the Sungai Tutong is typical of many tropical Asian slow-flowing rivers. The river had relatively warm temperatures, with a median from all 25 sites (sampling dates between June and December 2004) of 28.5 °C. The river was always visibly turbid, due primarily to high suspended sediment levels (median from all sites of 18 ppm). The river water was always acidic (median pH from all sites was 5.7) due to the acidic breakdown products of forest and wetland vegetation. The slow flow at most Sungai Tutong sites contributed to low oxygen saturation levels, with a median from all 25 sampling sites of 60 %; however, the faster flow of the Rambai bridge site produced a higher median dissolved oxygen saturation of 74.5 %.

Figures

FIGURES 1 – 4. Aphelocheirus bruneiensis sp. n. (1) Habitus of holotype, brachypterous male (body length 6.1 mm), dorsal aspect. (2) Habitus of paratype, macropterous male (body length 6.1 mm), dorsal aspect. (3) Habitus of paratype nymph (body length 5.1 mm), dorsal aspect. (4) Type locality. 1 – 3: © NHMW Hemiptera Image Collection, published with permission. 4: photo by © Stephen Moore.

FIGURES 5 – 10. Aphelocheirus bruneiensis sp. n., holotype, male. (5) Mesosternal carina (mstc) and propleuron (ppl), ventrolateral (slightly caudal) aspect. (6) Genitalia, dorsal aspect, after removing the parameres: aed - mainpiece of aedeagus with bulbous outgrowths on both sides; lpa – left parandrium; pyg – pygophore, rpa – right parandrium. (7, 8) Left paramere, approximately dorsal and ventral aspects. (9, 10) Right paramere, approximately ventral and dorsal aspects.