Eotrechus siamensis Vitheepradit & Sites, 2007, sp. n.
Creators: name: Vitheepradit, Akekawat
name: Sites, Robert W.
Publisher: name: Zenodo
Year: 2007
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Hemiptera
Gerridae
Eotrechus
Eotrechus siamensis

description: Eotrechus siamensis sp. n.
Figs. 3–5.
Descriptions. WINGLESS MALE. Holotype, body length 7.64; width of head across eyes 1.68; maximum width across mesocetabula 2.36. Paratypes (n = 8), body length 7.30–7.64 (mean = 7.45); width of head across eyes 1.60–1.72 (mean = 1.66); maximum width across mesocetabula 2.28–2.48 (mean = 2.38). Dorsal coloration mainly black with numerous short, gold setae; brownish-yellow markings on lateral and posterior portions of head, medial portions of pro- and mesonotum (Figs. 3 a, b). Ventral coloration mainly brown except brownish-yellow head, prosternum, and abdominal sternum VIII; dark brown metasternum and abdominal sternum II; covered with numerous gold setae.
Head. Black with brownish-yellow basal band and lateral markings in front of eyes (Figs. 3 a, b); length of head 1.36; antennae slightly shorter than body, dorsally with segment I brown with black proximal and distal tips and 4–6 spines on distal ¼, segments II–IV dark brown; lengths of segments I–IV = 2.16: 1.56: 1.08: 1.52. Eyes silvery-red, length of eye 0.76, synthlipsis 0.66. Rostrum mainly brownish-yellow, segment IV and midline of segment III black to dark brown, well surpassing procoxae.
Thorax. Pronotum shorter than head (1.04: 1.36), with yellowish-brown stripe on midline (Fig. 3 a). Mesonotum with broad yellowish-brown stripe on midline expanding laterally in anterior half and forming Wshaped marking in posterior half. Metanotum black with faint brown medial stripe in posterior half. Pleuron and acetabula mainly black, except propleuron with two brownish-yellow longitudinal stripes (Fig. 3 b) and mesopleuron with large brownish-yellow patch ventrally; silvery setae as large patches on pro- and mesoacetabula (viewed best with dry specimen), lateral surface of metacetabulum, ventral half of mesopleuron, and thin longitudinal stripe in dorsal half of mesopleuron. Sterna mainly brown and covered with silvery pubescence. Prosternum mostly yellowish-brown. Meso- and metasterna entirely black, covered with silvery pubescence; mesosternum 3.14x length of metasternum (2.20: 0.70); metasternum depressed medially at posterior margin.
Legs. Mainly brownish-yellow. Fore femur with brown stripe on anterior margin, moderately incrassate with tubercle 1/4 distance from proximal end, followed by excavation (Fig. 4 a); length 5.14x maximum width (2.88: 0.56); ventral surface with 2–4 stout black bristles. Fore tibia brownish-yellow and almost straight except slightly curved distally with long, dark brown setae; inner apical process blunt (Fig. 4 a). Fore tarsus dark brown; covered with numerous stout, dark brown setae. Claws stout (length 0.24–0.26). Middle and hind legs with femora brownish-yellow, dark brown on distal ends, thickened proximally (0.30, 0.30), slightly shorter than body length, covered with scattered stout, dark brown spines on inner surface. Tibiae brown; covered with scattered stout, dark brown spines becoming more dense distally. Tarsi dark brown, covered with numerous dark brown spines on inner surface, becoming obsolete distally on tarsomere II. Leg measurements as follows: foreleg, femur = 2.88, tibia = 2.56, tarsomere I = 0.26, tarsomere II = 0.46; middle leg, femur = 7.55, tibia = 6.39, tarsomere I = 0.68, tarsomere II = 0.74; hind leg, femur = 7.47, tibia = 7.14, tarsomere I = 0.72, tarsomere II = 0.76.
Abdomen. Tergites I–VII black, shiny medially, covered with short gold setae; tergite I with a faint medial brown marking on anterior 1/4; tergites V–VII with medial brown stripe becoming larger posteriorly; tergite VIII black, covered with long, golden-brown setae. Connexiva mainly brown, black mesally, covered with gold setae. Sterna II–VII length 1.44, sterna II–VI with median brownish-yellow groove becoming slightly narrower posteriorly (Fig. 3 c). Sternum VII longer than combined lengths of V and VI (0.42: 0.38); median sublyre-shaped depression; broad, angular notch on posterior margin (Figs. 3 c, 4b) with long, brown setae (Fig. 3 c). Sterna VIII and IX (genital segment) relatively large, length 1.28. Sternum VIII depressed medially and along anterior margin, covered with long brown setae posterolaterally, posterior margins convergent, tuberculate medially (Fig. 3 c). Pygophore stout, ovate, with bifid tip (Figs. 4 b, 5a); covered with long, stout, brown hairs laterally and posteriorly (Figs. 5 a, b). Parameres short, stout (Fig. 5 a). Proctiger with raised median lobe (lateral view), lateral wings covered with dense patch of long brown hairs laterally (lateral and dorsal views) (Figs. 5 c, d).
WINGLESS FEMALE. Allotype, length 8.05; width of head across eyes 1.68; width of thorax across mesoacetabula 2.60. Paratypes (n = 6) length, 7.89–8.72 (mean = 8.26); width of head across eyes 1.64–1.80 (mean = 1.70); width of thorax across mesoacetabula 2.44–2.68 (mean = 2.55). Similar to wingless male in general structure and coloration with following exceptions: Ventral coloration mainly yellowish-brown; length of head 1.12; length of eye 0.72; synthlipsis 0.72. Antennal segment lengths: 1.68: 1.36: 0.92: 1.60. Pronotum shorter than head (0.98: 1.12). Mesosternum 2.84x length of metasternum (2.16: 0.76). Fore femur without tubercle, ventral surface with 12 stout, black hairs; length 7.22x maximum width (2.60: 0.36). Middle and hind claws stout (length: 0.20, 0.20). Middle and hind femora thickened basally (width: 0.30, 0.24). Leg measurements as follows: foreleg, femur = 2.60, tibia = 2.24, tarsomere I = 0.18, tarsomere II = 0.54; middle leg, femur = 6.97, tibia = 6.06, tarsomere I = 0.68, tarsomere II = 0.68; hind leg, femur = 7.06, tibia = 6.64, tarsomere I = 0.72, tarsomere II = 0.70. Abdominal sterna II–VII length 2.68, without median groove; sternum VII longer than combined lengths of sterna V and VI (0.98: 0.76), with posterior margin concave. Genital segments (VIII and IX) 0.44, not concealed (lateral view) (Fig. 4 c). Proctiger long, with roundly triangular posterior tip (dorsal view).
WINGED MALE (n = 6). Similar to wingless male in general structure and coloration with following exceptions: Ventral surface darker, length 7.64–7.97 (mean = 7.76); width of head across eyes 1.64–1.68 (mean = 1.67); width of thorax across mesoacetabula 2.28–2.44 (mean = 2.37). Pronotal posterior lobe entirely black and shiny medially, with short gold setae. Wings exceeding tip of abdomen, dark smoky-brown, costal margin and veins black; veins and some cells covered with small short gold setae; length of forewing along costal margin 5.89–6.23 (mean = 6.03). Mesopleuron entirely black.
WINGED FEMALE (n = 6). Similar to wingless female in general structure and coloration with the following exceptions: Ventral surface darker, length 8.30–9.13 (mean = 8.81); width of head across eyes 1.60– 1.72 (mean = 1.67); width of thorax across mesoacetabula 2.32–2.72 (mean = 2.51). Pronotal posterior lobe entirely black with short, gold setae. Wings exceeding tip of abdomen; dark smoky-brown; costal margin and veins black; veins and some cells covered with short, gold setae; length of forewing along costal margin 6.06– 6.56 (mean = 6.32). Mesopleuron entirely black.
Diagnosis. Males of E. siamensis can be distinguished from those of Thai congeners by a stout pygophore with a bifid tip and without posterolateral projections. In contrast, E. elongatus has an elongate pygophore with a blunt tip; E. hygropetricus has a rounded pygophore; E. petraeus and E. romglao have a pygophore with a triangular tip; and E. kalidasa has a pygophore with elongate posterolateral projections.
Females of E. siamensis can be distinguished from those of E. hygropetricus by the trochanter of the foreleg without dark spines, whereas the latter species has dark spines. Females of E. siamensis can also be distinguished from those of E. kalidasa by the mesosternum almost three times longer than the metasternum, whereas in the latter species the mesosternum is less than twice as long as the metasternum (Andersen 1982a). Females of E. siamensis can be distinguished from those of the other Thai congeners by the concave posterior margin of sternum VII, whereas the margin is straight in E. elongatus, E. petraeus, and E. romglao.
Etymology. This species is named after its country of origin.
Discussion. In the only key to species of Eotrechus (Andersen 1982a), E. siamensis males key to the fourth couplet and females to the eighth couplet. Males of E. siamensis and E. pingae Andersen from China share a similar pygophore structure, which is produced posteromedially, although the pygophore of E. siamensis is acutely bifid whereas that of E. pingae is roundly bilobed. The type locality is a pristine waterfall in a well forested area in the northern part of Doi Inthanon, which is the upper part of the Thanon Thong Chai Mountain Range in Chiang Mai Province. More specifically, this species occurred on the near-vertical rock surfaces of waterfalls, which are covered with moss and ferns and a very thin layer of water (Fig. 1). Specimens were also collected from similar habitats on other waterfalls on Doi Inthanon and Doi Suthep. Moreover, both winged and wingless forms were found nearly throughout the year at waterfalls on Doi Inthanon. This species occurred synoptically with E. hygropetricus and E. petraeus at Huay Sai Luang and Siriphum waterfalls on Doi Inthanon, and Sai Yoi Waterfall on Doi Suthep.
Material examined. Holotype, wingless male, and allotype, wingless female: THAILAND: Chiang Mai Prov.: Doi Inthanon NP, Pha Dum Waterfall, 18°36'N 98°31'E, 1379 m, 3-V-2003, UMC and CMU teams, L- 499. Paratypes, 2 wingless males, 7 winged males, 3 wingless females, 6 winged females, same data as holotype; 6 wingless males, 3 wingless females, Doi Suthep-Pui NP, Siriphum Waterfall, 18°32'N 98°31'E, 1380 m, 2-VI-2002, UMC and CMU teams, L-317.
Additional material examined. THAILAND: Chiang Mai Prov.: 5 winged males, 2 wingless females, 3 winged females, same data as holotype; Doi Inthanon NP, Huay Sai Luang Waterfall, 18°31'N 98°27'E, 1060 m, 20-III-2002, R. W. Sites, A. Vitheepradit, K. Kirawanich, L-311; 1 winged male, 2 winged females, same locality, 4-VI-2002, UMC and CMU teams, L-322; 1 wingless female, same locality, 6-VII-2004, CMU team; 1 wingless male, 1 wingless female, same locality, 11-VIII-2004, CMU team; 2 winged females, same locality, 6-IX-2002, CMU team; 1 wingless female, 1 winged female, 22-X-2002, CMU team; 1 winged male, 1 wingless female, same locality, 14-XI-2002, CMU team; 1 winged male, same locality, 13-I-2003, CMU team; 1 wingless female, same locality, 16-II-2002, CMU team; 2 wingless males, 14-III-2003, CMU team; 1 wingless male, 1 winged male, Doi Suthep-Pui NP, Siriphum Waterfall, 18°32'N 98°31'E, 1380 m, 11-IV- 2000, G. W. Courtney; 2 wingless females, 2 winged females, same locality, 2-III-2002, A. Vitheepradit and K. Kirawanich, L-249; 1 winged female, same locality, 2-VI-2002, UMC and CMU teams, L-317; 3 winged females, same locality, 9-V-2002, CMU team, L-401; 1 wingless male, same locality, 8-VI-2002, CMU team; 1 wingless male, 1 wingless female, 10-VIII-2002, CMU team; 1 winged male, 1 winged female, same locality, 14-XI-2002, CMU team; 2 wingless females, same locality, 8-XII-2002, CMU team; 1 winged female, same locality, 13-I-2003, CMU team; 1 winged male, same locality, 16-II-2003, CMU team; 1 winged female, same locality, 14-III-2003, CMU team; 1 wingless female, same locality, 3-IV-2003, UMC and CMU team, L- 441; Doi Suthep-Pui NP, Sai Yoi Waterfall, 18°48'N 98°55'E, 1100 m, 8-X-2002, CMU team; 1 winged female, same locality, 13-I-2003, CMU team.
description: Published as part of Vitheepradit, Akekawat & Sites, Robert W., 2007, A review of Eotrechus Kirkaldy (Hemiptera: Heteroptera: Gerridae) of Thailand with descriptions of three new species, pp. 1-19 in Zootaxa 1478 on pages 2-8, DOI: 10.5281/zenodo.176807