Research Article |
Corresponding author: Subramanian Apadodharanan ( subbuka.zsi@gmail.com ) Academic editor: Dávid Rédei
© 2014 Subramanian Apadodharanan, Srimoyee Basu, Herbert Zettel.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Apadodharanan S, Basu S, Zettel H (2014) A new species of Onychotrechus Kirkaldy, 1903 (Hemiptera, Heteroptera, Gerridae) from Dooars, West Bengal, India, and a key to males of all species. Deutsche Entomologische Zeitschrift 61(2): 133-139. https://doi.org/10.3897/dez.62.8154
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A new species of hygropetric water strider, Onychotrechus dooarsicus sp. n. is described from Buxa Tiger Reserve, Dooars, West Bengal, India. Representatives of the new species were collected from a stream with boulders and rocks splashed by water, with slow current, situated at an altitude of 630 m a.s.l. This is the seventh species of Onychotrechus confirmed for India. The new species is closely related with O. robustus Andersen, 1980 from northwestern India and O. jaechi Zettel & Tran, 2007 from Bhutan. An identification key to males of all species of Onychotrechus species is also provided.
Eotrechinae, Buxa Tiger Reserve, Jalpaiguri
The hygropetric water striders of the genus Onychotrechus Kirkaldy, 1903 are members of the subfamily Eotrechinae and chiefly distributed on the Indian subcontinent and Sri Lanka (11 species, including the new one), but two species inhabit southeastern Asia (
Species of Onychotrechus are mostly found resting, walking, running or jumping on the wet seeping rock faces covered with algae or splashed by water of small mountainous streams. Both nymphs and adults, including copulating individuals, can be encountered in their typical habitats. Although their coloration appears vivid, it is cryptic and makes them difficult to recognize in the dark wet rocks. The hygropetric way of life is a secondary adaptation evolved from life on water surface in this group (
Hitherto, six species of Onychotrechus have been recorded from India (
In a recent expedition to the Buxa Tiger Reserve, near the Indo-Bhutan border of West Bengal, the second author collected a specimen, that is herein described and named as Onychotrechus dooarsicus sp. n.
Specimens were collected by a short-handled aquatic net and preserved in 70% ethyl alcohol (C2H5OH). Samples were identified using a binocular microscope Leica M205A and body parts were photographed. Male genitalia was dissected and kept in 10% KOH for 30 minutes to clear the hard sclerotized structure and drawings were prepared using a camera lucida attached to the Leica M205A binocular microscope. Identified specimens were deposited in the National Zoological Collections of Zoological Survey of India, Kolkata. All measurements are given in millimetres.
(apterous male): INDIA: West Bengal; Jalpaiguri; Buxa Jhora near Buxa fort; Buxa Tiger Reserve, 26.76223° N, 89.59968° E, 630 m a. s. l., 19.IV.2013, Srimoyee Basu (Reg. No.: 3130/H15). Paratypes: one apterous male, one apterous female, same data as holotype (Reg. No.: 3131/H15).
INDIA: West Bengal; Jalpaiguri; Buxa Jhora near Buxa fort; Buxa Tiger Reserve; stream with large rocks, stones in forested areas.
(Fig.
Colour: Body dorsally black with yellow markings. Head with a median yellow longitudinal stripe, which ends in a blunt arrow head (Fig.
Onychotrechus dooarsicus sp. n. 6. Mesosternum of male, ventral view. 7. Lateral view of female. 8. Forefemur of male. 9. Foretibia and tarsi of male. 10. Foreleg of female. 11. Foreleg claws in male. 12. Abdominal tergites of male. 13. Abdominal sternites with genital segments in male.
(measurements refer to holotype). Head length 0.64, width 0.89. Interocular width 2 times as large as eye width (0.45: 0.22). Eye length 0.44. Length of antennal segments 1-4: 0.96, 0.94, 0.89, 1.38; first antennomere with three spines distally, being two long, and a small one arising near base of first spine. Rostrum reaching up to mid-way of mesosternum, length 1.50.
Pronotum 0.84 mm in width; pronotum length 0.53, width 0.79. Combined length of mesonotum and metanotum 1.12, width 0.98. Mesosternum (Fig.
Measurements (value in mm) of leg segments of apterous males and female of Onychotrechus dooarsicus sp. n.
Leg | Femur | Tibia | Tarsus 1 | Tarsus 2 |
---|---|---|---|---|
Foreleg: ♂♂ ♀ |
1.15, 1.17 1.36 |
0.99, 1.1 1.17 |
0.07, 0.08 0.12 |
0.19, 0.22 0.28 |
Mid leg: ♂♂ ♀ |
3.71, 3.72 4.03 |
2.54, 2.56 2.70 |
0.15, 0.16 0.19 |
0.26, 0.28 0.29 |
Hind leg: ♂♂ ♀ |
3.80, 3.81 4.36 |
2.62, 2.63 3.09 |
0.13, 0.15 0.24 |
0.34, 0.36 0.41 |
Abdomen (Figs
Genitalia (Figs
(Figs
Colour: Almost identical to male, with the following exceptions: posterior yellow mid-line lacking from metanotum (Fig.
Structural characteristics: Length of head 0.75, width 0.91. Interocular width 0.52. Eye length 0.42, width 0.23. Length of pronotum 0.51, width 0.85. Length of antennal segments 1-4: 1.10, 1.08, 1.04, 1.48. Combined length of meso- and metanotum 1.38, width 1.36. Forefemur slender (Fig.
Unknown.
Onychotrechus dooarsicus sp. n. is probably a close relative of O. jaechi, recently described from Bhutan. They share some common characters: males have almost identical pro-, meso- and metasternal markings, basally incrassate forefemora, similar mesosternal modifications and short abdominal segments. However, the male of O. dooarsicus sp. n. distinctly differs from O. jaechi by the following characteristics: 1) The foretibia of O. dooarsicus sp. n. bears a patch of few short setae basally on flexor side, and a soft spinous structure protruding outwards from the base of the curvature; its apical region bears two prominent black spines (forming a ‘V’), four black spines and a row of short setae towards extensor side; whereas, in O. jaechi its base bears a patch of long hairs on the flexor side and the distal modifications are absent. 2) The mesosternum of O. dooarsicus sp. n. has a median narrow groove that is slightly widened posteriorly, whereas O. jaechi has a strongly modified mesosternum, with a medial, posteriorly widened depression and a prominent transverse swelling at its hind margin. 3) In O. dooarsicus sp. n., the paramere has a notch at mid-length, that is absent from O. jaechi. The female of O. jaechi is unknown.
The specific epithet ‘dooarsicus’ comes from its place of occurrence, ‘Dooars’ of West Bengal. Dooars is a large region, forming the gateway from India to Bhutan and stretching from the plains of Darjeeling District, Jalpaiguri District, and the upper regions of Cooch Behar District of West Bengal to some parts of Assam. This part mainly consists of Himalayan foothills.
Representatives of this species have been found in the shallow zone between the rocks, splashed by a slow-flowing stream (630 m), known as Buxa Jhora, located near Buxa fort of Buxa Tiger Reserve Range.
Note: The authors were able to study male specimens of most species, but not of O. baijali and O. singalensis. For these species characters were taken from the original descriptions.
1 | Forefemur at flexor side with one or two prominent spine-like structures usually consisting of densely-packed setae | 2 |
– | Forefemur at flexor side without prominent spine-like structures | 4 |
2 | Forefemur at flexor side with two spine-like structures, one sub-apically and another one at mid-length. (India: Tamil Nadu) | O. baijali |
– | Forefemur at flexor side with one spine-like structure sub-apically | 3 |
3 | Forefemur at flexor side between base and spine-like group of setae with row of long flexible setae; at extensor side basally with a few short spiny setae. (India: Karnataka) | O. rupestris |
– | Forefemur at flexor side without long flexible setae; at extensor side basally without spiny setae; spine-like group of setae on a tubercle. (India: Karnataka, Kerala, Maharashtra) | O. spinifer |
4 | Forefemur strongly incrassate (Fig. |
5 |
– | Forefemur relatively slender, more than 6 times as long as wide | 7 |
5 | Foretibia weakly curved, chiefly in basal third. Mesosternum posteriorly with short black pegs. Middle femur with row of relatively long, erect spines near base. (India: Himachal Pradesh, Uttar Pradesh) | O. robustus |
– | Foretibia strongly curved (Fig. |
6 |
6 | Flexor side of foretibia basally with patch of long hairs and apically without prominent spines. Mesosternum with median groove posteriorly strongly widened and posterior margin with strong, transverse swelling. Paramere without median notch. (Bhutan) | O. jaechi |
– | Flexor side of foretibia basally with patch of few short hairs and apically with two prominent black spines (Fig. |
O. dooarsicus sp. n. |
7 | Large species; body length (from apex of head to tip of proctiger) 5.8 mm or more. (India: Kerala, Maharashtra) | O. major |
– | Small species; body length (from apex of head to tip of proctiger; excluding wings) 5.2 mm or less | 8 |
8 | Dark markings of body much reduced; colour chiefly pale | 9 |
– | Dark markings of body prominent | 10 |
9 | Middle and hind claws shorter than first tarsomeres. (Sri Lanka) | O. singalensis |
– | Middle and hind claws longer than first tarsomeres. (Malaysia: Penang, Selangor) | O. pallidus |
Note: Besides colour, O. pallidus differs from O. esakii (couplet 12), which is common in southeastern Asia, by the more slender forefemur and by small shiny areas on thoracic nota (often completely absent from pronotum and metanotum), whereas these areas are much expanded in O. esakii (in macropterous morph prominent on pronotum, but absent from pronotal lobe). | ||
10 | Metasternum laterally with one pair of round tubercles. (Sri Lanka) | O. tuberculatus |
– | Metasternum without pair of tubercles | 11 |
11 | Forefemur relatively slender, almost evenly tapering from base to sub-apex, width at midlength less than 2 times maximum width of foretibia; its flexor side at base with conspicuous and long patch of black pegs surpassing midlength. (India: Karnataka, Kerala, Maharashtra, Rajasthan, Tamil Nadu) | O. rhexenor |
– | Forefemur distinctly thickened in basal two thirds, width at midlength clearly more than 2 times maximum width of foretibia; its flexor side with inconspicuous patch of pale or minute pegs not surpassing midlength of femur | 12 |
12 | Forefemur suddenly narrowed sub-apically (more distinct in apterous morph); its flexor side with patch of minute black pegs. Distal part of paramere relatively slender, apically rounded. (widely distributed in southeastern Asia: Myanmar, southern China, Thailand, Vietnam, West Malaysia) | O. esakii |
– | Forefemur evenly narrowed in distal third; its flexor side with indistinct patch of pale pegs. Distal part of paramere relatively wide, with distinct apex. (Sri Lanka) | O. sakuntala |
The genus Onychotrechus shows its maximum diversity in southern India (Kerala, Karnataka, Tamilnadu) (
Species identification of eotrechine water striders is usually based on the strongly modified genitalia of the males (see, e.g.,
The authors are grateful to the Dr. K. Venkataraman, Director of the Zoological Survey India, for his continuous support and encouragement. We are thankful to the West Bengal Forest Department for providing the necessary permissions to conduct the study. The authors express their sincere gratitude to the late Dr. G. Thirumalai, Sc.-F, for his constant encouragement during the research. Special thanks to Prof. G.K. Saha, Department of Zoology, and University of Calcutta, for his constant support and guidance. Thanks are due to Miss E. Jehamalar, J.R.F., for helping throughout the study. The services of Mr. and Mrs. S. Basu, Mr. S. Paul and Mr. S. Saha in assisting during field surveys are also thankfully acknowledged.