Namtokocoris Sites

Sites, Robert W. & Vitheepradit, And Akekawat, 2007, Namtokocoris Sites, a new genus of Naucoridae (Hemiptera: Heteroptera) in waterfalls of Indochina, with descriptions of six new species, Zootaxa 1588, pp. 1-29 : 2-6

Namtokocoris Sites , NEW GENUS

Figs. 1 , 2, 10–14

Type species— Namtokocoris siamensis Sites , NEW SPECIES

Description. Length 6.64–10.21, width 4.23–6.47. Body ovate, macropterous; widest across embolia; dorsoventrally robust for the subfamily; convex dorsally, flattened ventrally; broadly rounded anteriorly and posteriorly; dorsally head and pronotum light colored, heavily covered with brown punctures; wings dark. Finely punctate throughout; head with compound eyes strongly divergent, mesal and lateral margins slightly convergent anteriorly; lateral hyperoche widening anteriorly; series of several setal rosettes paralleling inner margin of eye; posterior margin of head slightly convex between eyes; apex of head deflexed, oriented posteriorly; labrum broad, rounded; rostrum short, segment three (first visible) partially concealed behind labrum, segment four narrower, reaching to middle of prothoracic coxae; antennae pale, segments one and two short and inconspicuous, three longest and widened apically, four half length of three. Pronotum concave behind eyes, dark band at anterior margin between eyes, covered with erect setae; lateral margins smooth, posterior margin broadly convex, transverse sulcus setting off more darkly colored posterior one third; propleura meeting prosternum; prosternal midline with expansive, thin, plate-like carina between coxae ( Fig. 1 b). Scutellum large, raised above level of wings, with pair of distinct protuberances ( Fig. 1 a), posterolateral margins sinuate. Mesosternum with broad tumescence, deeply inflected at midline. Meso- and metapleuron with dense patch of scale-like hairs along lateral margin; metaxyphus acuminate posteriorly. Forelegs with femur broad; tibia narrow; tarsi single-segmented in both sexes; single claw in both sexes, very short, conical ( Figs. 1 c, d). Middle and hind femora with anteroventral row of hairs and posteroventral row of short spines; middle femur curved dorsad and twisted ~45o, hind femur flat. Middle tibia short, stout; male with dense pad of hairs beginning at middle of ventral surface and widening distally, pad reduced on female; single row of posteroventral heavy spines, multiple rows of anterior heavy spines, single row of short spines on dorsal surface. Hind leg with tibia elongate, thin, multiple rows of spines on anterior and posterior margin, swimming hairs on tibia continuing onto tarsi; tarsomere one short and produced beneath base of tarsomere two, two long, three longer and with well-developed unguifer; tarsi with heavy spines. Mid- and hind pretarsi with elongate empodia; claws long, curved, each with basal tooth. Mesothoracic coxae slightly and metathoracic coxae strongly recessed within thoracic venter; coxae with series of stout hairs along ventromesal ridge. Hemelytra with distinct clavus and embolium; clavus with longitudinal suture between claval suture and scutellum; multiple linear series of elongate, stout, slightly scale-like setae, including several longitudinal series within clavus, one extending from end of embolar suture, pair of short series flanking claval commissure and diverging posterolaterally, curved series beginning in middle of right corium extending posterolaterally and curving back posteromesally and then anteromesally to form open loop, series on left corium outlining edge where right wing overlaps. Single setae not in series scattered generally over surface. Membrane present but reduced, not obvious, but more flexible than corium and rugose along outer margin (rugosity evident with transmitted light and held at oblique angle). Hindwing with well-developed veins C, R, M, Cu, pCu, pCu-A, 1A, 2A; cells R, M; anal fold ( Fig. 2). Abdomen dorsally brown, terga I-IV entire; V-VII dissociated into medio- and laterotergites in males, entire in females. Connexival margin smooth and continuous, without posterolateral segmental productions. Abdomen ventrally generally covered with fine, light colored setae; with glabrous lateral band set off by line of stout, elongate, erect setae; strong brush of brown hairs beginning near anterior margin of V, widening and continuing to posterior end of abdomen. Lateral margins of laterosternites III-VII with series of stout spines (absent anteriorly on III and IV; weakly developed on VI and VII), spines accompanied by elongate hairs. Spiracle on II at anterior margin concealed beneath metepimeron, spiracles III-VI evident between and slightly anterior to paired glabrous patches. Male with aedeagus elongate, linear, nearly straight on left margin, curved along right margin and tapered distally, with series of striations on left, right, or both sides of median carina; parameres small, symmetrical; right side of median process of pygophore and right paramere slightly deflected ventrad. Female subgenital plate elongate, subtriangular with apex rounded or flattened.

Diagnosis. This genus can be recognized by the pair of prominent protuberances ( Fig. 1 a) on the scutellum, the prosternal midline bears an expansive, thin, platelike carina ( Fig. 1 b); the forelegs of males have a one-segmented tarsus that appears fused with the tibia ( Figs. 1 c, d), although a suture is visible, as is common throughout the other naucorid subfamilies; and the forelegs of both sexes bear a single claw. Similar to Diaphorocoris, linear series of stout hairs occur on the hemelytra. Like Ctenipocoris, the body form is relatively dorsoventrally robust and the mid and hind legs are heavily spined. Like both of these genera, a very dense band of hairs begins near abdominal sternum V and gradually widens to the posterior tip of the abdomen.

Discussion. Males have the well-developed pad of hairs on the mesotibia (present but reduced in females), which is consistent with the subfamily Laccocorinae . However, both sexes have a single nonarticulated protarsal segment and single claw, which is inconsistent with established subfamily attributes. Intraspecific variation in aedeagal striations exists such that the striations might be apparent on both sides of the midline, or on only one side. Whether or not these striations have stridulatory function is unknown. The secondary longitudinal suture within the clavus was observed in all specimens examined, and appears to correspond with macroptery (H. Zettel, pers. comm.). All specimens examined for hindwing condition were macropterous.

The subfamily Laccocorinae has been characterized by somatic dimorphism of the forelegs and middle legs. Specifically, the forelegs of laccocorine males have two-segmented, articulated tarsi; whereas females have one-segmented, articulated tarsi. This condition as a unifying feature of the subfamily is vitiated by the discovery of Namtokocoris . However, other features of the subfamily hold consistent, including that laccocorine males have the mesothoracic tibia with a well-developed dense pad of hairs widening distally, and that in females this pad of hairs is weakly developed. In addition, the parameres are small, the labrum is well developed, and the morphological apex of the head is folded down and oriented posteriorly.

Based on the character states in common with other members of the subfamily, Namtokocoris appears to be most closely related to Diaphorocoris. Both genera have elevation and paired protuberances of the scutellum, and hair lines on the hemelytra (Table 1). These genera both have a dense midventral hair band in common with Ctenipocoris. Analysis including molecular data is needed to more effectively evaluate phylogenetic relationships.

TABLE 1. Character comparison of Namtokocoris with other Asian genera of Laccocorinae .

Character Namtokocoris Diaphorocoris Ctenipocoris Laccocoris Heleocoris dimorphic pad of hairs on mesotibia yes yes yes yes yes front of head folded posteroventrally yes yes yes yes yes well-developed labrum yes yes yes yes yes

Ecological Notes. All known species, described here, are restricted to the rock surfaces of waterfalls and nearby wet rocks receiving spray from the waterfalls ( Figs. 4–9 ). The insects have not been found in the plunge pool below the waterfall except after they fell in when dislodged from the rock. These insects are cryptic and difficult to see unless they move. They tend to occur away from the high shear forces of the waterfall, and there appears to be some species-specificity to the degree of hydraulic force they prefer. Most are at least in a film of sheeting water at the margins of the falling water. Frequently, they can be found in cracks or fissures of the substrate, beneath undercuts in the rock, or associated with rock surface irregularities. All species except two were found on rocks with gentle surface texturing. The two exceptions were a wet, smooth granite surface ( Fig. 5 ) and a moderately-deeply pocketed limestone surface ( Fig. 7 ). The latter was the only case in which we found Namtokocoris on a limestone waterfall, despite sampling many other limestone waterfalls. All other specimens were taken on granite. Algae was invariably present on the rocks wherever this insect was found. Many other insects were present on the rock surfaces of the waterfall, including mayflies, dryopoids, hydrophilids, earwigs, gerrids, and the naucorid Cheirochela . We have also encountered tadpoles, frogs, fish, and snakes on the near-vertical rock surfaces. A detailed account of species of Oocyclus (Hydrophilidae) corresponding with many of our localities in Thailand has been published by Short & Swanson (2005), and of Eotrechus (Gerridae) by Vitheepradit & Sites (2007a).

In northern Thailand, where surface water is present year round, Namtokocoris occurred continuously through an annual cycle. However, in the south during the dry season, some waterfalls in which the insects occur become dry to the point that no surface water is evident; nevertheless Namtokocoris persists and probably survives in protected wet cavities below the rock surface.

Waterfalls in southern Thailand from the border with Malaysia north to the area near Phuket in the Isthmus of Kra have been sampled for 15 years without discovering this insect. The farthest south we have collected Namtokocoris in Thailand is Ranong Province. We have collected it from throughout the rest of Thailand, including from <1 km from the border with Burma to the west, internationally between Thailand and Laos in the north, to near the Cambodian border in the southeast. In addition, we have collected it in southern and northern Vietnam. Thus, this genus unquestionably occurs widely throughout much of Indochina (Fig. 3).

Etymology. This genus is particularly common in Thailand where five of the six species described here were found. The genus is named for its restriction to a waterfall habitat. “Namtok” means waterfall in the Thai language, and “coris” is Greek for bug.

Material examined. See species localities.

Figures

FIGURE 1. Diagnostic features of Namtokocoris n. gen: a) scutellar protuberances, b) lateral view of midventral prosternal carina, c) male foreleg with one-segmented tarsus and single pretarsal claw, enlarged in (d), of Namtokocoris siamensis n. sp

FIGURE 4. Namtok Mohk Fah in Chiang Mai Province, Thailand, the type locality of Namtokocoris siamensis n. sp.

FIGURE 5. Namtok Haew Lome in Ranong Province, Thailand, the type locality of Namtokocoris akekawati n. sp.

FIGURE 6. Thac Dalanta in Lam Dong Province, Vietnam, the type locality of Namtokocoris dalanta n. sp.

FIGURE 7. Thac Kem in Nghe An Province, Vietnam, the type locality of Namtokocoris kem n. sp.

FIGURE 8. Namtok Khlong Lan in Kampaeng Phet Province, Thailand, the type locality of Namtokocoris khlonglan n. sp.

FIGURE 9. Unnamed roadside cascade in Kanchanaburi Province, Thailand, the type locality of Namtokocoris minor n. sp.

FIGURE 10. Holotypes of a) Namtokocoris siamensis, b) Namtokocoris akekawati, c) Namtokocoris dalanta, d) Namtokocoris kem, e) Namtokocoris khlonglan, and f) Namtokocoris minor.

FIGURE 11. Left margin of pronotum and embolium of macropterous a) Namtokocoris siamensis, b) Namtokocoris akekawati, c) Namtokocoris dalanta, d) Namtokocoris kem, e) Namtokocoris khlonglan, and f) Namtokocoris minor.

FIGURE 12. Genital capsule of males of a) Namtokocoris siamensis, b) Namtokocoris akekawati, c) Namtokocoris dalanta, d) Namtokocoris kem, e) Namtokocoris khlonglan, and f) Namtokocoris minor. Scale bar = 1.0 mm

FIGURE 13. Aedeagus with pygophore and dorsolateral aspect of right paramere (laid flat) of a) Namtokocoris siamensis, b) Namtokocoris akekawati, c) Namtokocoris dalanta, d) Namtokocoris kem, e) Namtokocoris khlonglan, and f) Namtokocoris minor. Sizes are not relative within or among species. See Fig. 12 for correct size relationships.

FIGURE 14. Ventral aspects of terminal abdominal segments of females of a) Namtokocoris siamensis, b) Namtokocoris akekawati, c) Namtokocoris dalanta, d) Namtokocoris kem, e) Namtokocoris khlonglan, and f) Namtokocoris minor.