Dineutus spinosus
Creators: name: Suksai, Benjamart
name: Gustafson, Grey T.
name: Sites, Robert W.
name: Sangpradub, Narumon
Publisher: name: Zenodo
Year: 2021
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Gyrinidae
Dineutus
Dineutus spinosus

description: Dineutus spinosus (Fabricius, 1781)
(Figs. 1F, 1J, 4C, 5J–M, 7C, 7E, 8A)
Material examined. THAILAND: Amnat Charoen Province: Kork Stream, Kham Khuean Kaeo Subdistrict, Chanuman District, 16°12'29.9"N 104°52'11.6"E, 188 m a.s.l., 23.XII.2017, leg. B. Suksai, 2 males, 4 females (THNHM). Kalasin Province: Phu Pan Natl. Park, water supply pond at Park HQ, 16°47'38.8"N 103°50'37.8"E, 7.VI.1998, leg. K.B. Simpson & A. Vitheepradit, L-165, 1 male (UMC). Mukdahan Province: Huai Lao Waterfall, Ban Kho Subdistrict, Khamcha-I District, 16°44'36.9"N 104°21'04.7"E, 226 m a.s.l., 22.XII.2017, leg. B. Suksai, 1 female (THNHM); Tadton Waterfall, Non Yang Subdistrict, Nong Sung District, 16°29'40.2"N 104°18'47.6"E, 208 m a.s.l., 22.XII.2017, leg. B. Suksai, 1 female (THNHM). Nakhon Ratchasima Province: Sakaerat Environmental Research Station, Bon weir, U-dom Sap Subdistrict, Wang Nam Khiao District, 14°29'49.2"N 101°54'55.5"E, 472 m a.s.l., 27.III.2018, leg. P. Chanteenok, 1 male (THNHM); same locality except for, 29.III.2018, leg. P. Chanteenok, 1 male, 1 female (THNHM); Thap Lan Natl. Park, Khok Krachai Subdistrict, Khon Buri District, 14°20'13.6''N 102°14'48.0''E, 224 m a.s.l., 27.IV.2014, leg. K. Piraonapicha, 7 males, 8 females (KKU, THNHM); same locality except for, Wang Tao Waterfall, Khok Krachai Subdistrict, Khon Buri District, 14°19'52.0''N 102°14'05.0''E, 224 m a.s.l., 23.III.2013, leg. K. Piraonapicha, 2 males, 4 females (KKU). Nakhon Si Thammarat Province: Chulabhorn District, 56 km N of Phatthalung, 8°03'N 99°53'E, 21 m a.s.l., 31.V.2003, leg. A. Vitheepradit & M.L. Ferro, L-583, 7 males, 6 females (UMC). Sisaket Province: Huay Sala Wildlife Sanctuary, Sum Sai Waterfall, 14°31.894'N 104°20.419'E, 202 m a.s.l., 12.IV.2004, leg. R.W. Sites & A. Vitheepradit, L-622, 5 males, 3 females (UMC). Songkhla Province: Prince of Songkla University, 2.V.1993, leg. Apinya, 1 female (UMC). Surat Thani Province: Ban Tha Rau Tai, Ban Na Doem District, 8°56.567'N 99°15.130'E, 4 m a.s.l., 20.VI.2004, leg. A. Vitheepradit & T. Prommi, L-782, 1 female (UMC). Ubon Ratchathani Province: Huay Sae Stream, Na Pho Klang Subdistrict, Khong Chiam District, 15°32'05.2"N 105°31'06.7"E, 131 m a.s.l., 23.XII.2017, leg. B. Suksai, 3 males, 2 females (THNHM).
Diagnosis. Male (Fig. 1F): Size: 6.4–8.0 mm. Body form oval; apex of flagellomere VI lightly colored; elytral apices weakly serrate, with parasutural and epipleural spines (Fig. 5J); lateral margin of pronotum and elytron orange or yellow (Fig. 1F); protrochanter apically with single series of few setae on ventral surface (Fig. 4C); profemur without sub-apicoventral tooth; protibia wedge-shaped; venter yellow to brown (Fig. 1J), epipleura yellow (Fig. 1J); aedeagus (Figs. 5K–L) with median lobe shorter than parameres, parallel-sided for 2/3 length, slightly narrowed in apical half, acuminate in apical fifth, with tip narrowly rounded, weakly straight in lateral view.
Female: Similar to male except for size: 6.9–8.1 mm; gonocoxae elongate, lateral margin rounded, apex weakly rounded (Fig. 5M).
Differential diagnosis. Dineutus spinosus can be distinguished from congeners in Thailand by the lightly colored margin of the pronotum and elytron and by the spinose elytral apex having both parasutural and epipleural spines developed (Table 1). No other species of Dineutus in Thailand has this combination of characters. Porrorhynchus marginatus has these features as well, but is much larger in size and can be distinguished by the elongate, triangular labrum in addition to other features of the forelegs.
Distribution. This is a widespread species found in the eastern portion of the Indian subcontinent and throughout Southeast Asia from Sri Lanka and eastern India through Assam, Bangladesh, Myanmar, Thailand, Laos, as far east as Vietnam (Ochs 1929, 1930; Mouchamps 1949; Brinck 1981; Vazirani 1984), and as far south as Singapore (Hendrich et al. 2004), Sumatra (Ochs 1929), and Borneo (Ochs 1928).
Habitat. It occurs on exposed rivers, streams, ponds, and water tanks (Figs. 7C, E). (Brinck 1981).
Discussion. Dineutus spinosus is currently known from only the northeastern and southern regions of Thailand (Fig. 8A) where it occurs at low to medium elevations (4–472 m a.s.l.). It has not been found at high elevation. We suspect that it might occur in other localities in Thailand with the same habitats at similar elevations. Both D. spinosus and the similar congener D. orientalis, which has a primarily more eastern and northern distribution, are known to co-occur in Laos and Vietnam (Mouchamps 1949; Brinck 1981). The latter species has yet to be encountered in Thailand and was not found during our surveys, despite extensive sampling in northeastern Thailand near the Laotian border (Fig. 8A).
description: Published as part of Suksai, Benjamart, Gustafson, Grey T., Sites, Robert W. & Sangpradub, Narumon, 2021, The Gyrinidae (Coleoptera) fauna of Thailand: Key to tribes and genera, with new records and keys to species of Dineutini and Gyrinini, pp. 97-117 in Zootaxa 5071 (1) on pages 106-108, DOI: 10.11646/zootaxa.5071.1.5, http://zenodo.org/record/5723327