Mesovelia horvathi Lundblad, 1933

Jehamalar, E. Eyarin, Chandra, Kailash & Polhemus, Dan A., 2019, Review of the Mesovelia horvathi species complex (Hemiptera: Gerromorpha: Mesoveliidae), with the description of seven new species from India, Zootaxa 4651 (3), pp. 471-496 : 473-476

Mesovelia horvathi Lundblad, 1933

( Figs. 1 A–F)

1933. Mesovelia horvathi Lundblad, Arch. Hydrobiol. Suppl. , 12, 190.

Material examined. INDONESIA, SUMATRA, Sumatera Utara Province, 2 apt. ♂, 1 apt. ♀, Kab. Simalungun, Kec. Jorlan Hataran, swift river above Tigadolok, 18 km E. of Prapat , 1000 m a.s.l., vic. 2.76750 0 S, 98.98889 0 E, 8.xi.1985, CL 2189, D.A. Polhemus & J.T. Polhemus ( BPBM) ; 1 apt. ♂, Kab. Tapanuli Tengah, Kec. Barus Utara, swift rocky hill stream in primary lowland rainforest, 15 km NW of Barus on Pakkat to Barus road, 150 m a.s.l., vic. 2.08833 0 S, 98.46583 0 E, 10.xi.1985, CL 2194, D.A. Polhemus & J.T. Polhemus ( USNM, BPBM) . Bengkulu province, 1 apt. ♀, Kab. Rejang Lebong, Kec. Birmani Ulu, Hutabarna River at Tabarenah, 7 km W. of Curup , 600 m a.s.l., 3.44000 0 S, 102.5097 0 E, water temp. 23.5° C., 7.ix.1991, CL 2582, D.A. Polhemus & J. T. Polhemus ( BPBM) .

Redescription. Apterous male: ( Figs. 1 A–F). Body length 2.24 (2.20–2.40, n=3), body width at metanotum 0.60, body width at tergum IV 0.60 (n=3).

Colour. Yellowish brown; dorsum of body covered with minute pale setae; antenna yellowish brown; rostrum yellowish brown with apex of fourth article darkened; legs including tarsi and claws uniformly yellowish brown; setiform spines on appendages black.

Structural characters. Frontoclypeal region with 6–8 thick setae. Head length 0.55, head width across eyes 0.45; synthlipsis (minimum interocular distance) 0.20; eye length 0.20, eye width 0.10. Lengths of antennomeres I–IV 0.45, 0.30, 0.80, 0.75.

Pronotal length 0.17, width 0.55; mesonotal length 0.15, width 0.56; metanotal length 0.10, width 0.55. Lengths of leg segments: foreleg: femur 0.70, tibia 0.65, tarsomeres I–III 0.03, 0.05, 0.09; mid leg: femur 0.80, tibia 0.90, tarsomeres I–III 0.04, 0.15, 0.11; hind leg: femur 1.10, tibia 1.55, tarsomeres I–III 0.05, 0.21, 0.15. Widths of fore, mid, hind femora 0.10, 0.10, 0.12. Flexor region of all femora lacking subapical spines; hind tibia sparsely clothed with medium sized spines on flexor margin, bearing 5–6 longer dark spines along extensor margin.

Dorsal abdominal length 1.23; terga I–VIII 0.15, 0.15, 0.10, 0.10, 0.15, 0.13, 0.20, 0.30; sterna IV–VIII 0.10, 0.10, 0.14, 0.15, 0.12. Combined length of abdominal sterna V–VII 0.40. Basal region of sternum VIII sublaterally with pair of dark brown spiniform setal tufts, each tuft with 6–7 spiniform setae arranged irregularly ( Fig. 1C ); sternum VIII midlaterally at level of posterior margin with very small tubercle (more evident in alcohol after dissection); inner length of spiniform setal tuft on sternum VIII 0.09, basal width 0.04, width between two tufts 0.11; without any space between posterior margin of abdominal sternum VII and anterior margin of spiniform setal tuft. Terminalia: anterior part of proctiger longer than bowl-shaped posterior part, clothed with long setae posteriorly, posterior part ventromedially convex, not excavated, median lateral process long, with acute tip ( Fig. 1D ); paramere slightly broad basally, medially not twisted, apical part tapering, gently curved on ventral margin ( Fig. 1E ), paramere, when attached to pygophore, with apical part slightly curved and directed laterad in lateral view ( Fig. 1E ) and in dorsal view tip directed anterad ( Fig. 1D ).

Apterous female. Colour: similar to apterous male. Body length 2.60 (2.30–2.60, n=2), width across metanotum 0.70, width across tergum IV 0.90 (0.85–0.90, n=2), head length 0.55, head width 0.52, eye length 0.19, eye width 0.13, synthlipsis 0.25; lengths of antennomeres I–IV 0.45, 0.35, 0.76, 0.75; pronotal length 0.20, width 0.60, mesonotal length 0.15, width 0.65, metanotal length 0.10, width 0.68. Lengths of leg segments: foreleg: femur 0.65, tibia 0.70, tarsomeres I–III 0.03, 0.06, 0.10; mid leg: femur 0.90, tibia 0.87, tarsomeres I–III 0.03, 0.15, 0.11; hind leg: femur 1.05, tibia 1.60, tarsomeres I–III 0.05, 0.25, 0.20. Widths of fore, mid, hind femora 0.08, 0.11, 0.14. Flexor regions of fore and mid femora subapically lacking spines.

Dorsal abdominal length 1.46, lengths of abdominal terga III–VIII, 0.50, 0.15, 0.15, 0.20, 0.22, 0.20; proctiger 0.14, dorsal gonoplac length 0.07, abdominal sterna V–VII, 0.13, 0.13, 0.15, abdominal length from sternum VIII to abdominal tip 0.62; combined length of abdominal sterna V–VII 0.41; maximum connexivum width at tergum V 0.25, ventral abdominal length from sternum V to abdominal tip 1.10.

Distribution. Australia, Indonesia, Papua New Guinea, Japan, China, Indonesia, Malaysia, Myanmar, Philippines, Singapore, Taiwan, Cambodia, Thailand and Vietnam (J. Polhemus & D. Polhemus 2000, Damgaard et al. 2012, D. Polhemus 2017).

Type repository. Male and female syntypes ( Damgaard et al. 2012) (Lectotype not designated): Indonesia, Java, Ranu Lamongan and Ranu Pakis and Sumatra, Lake Ranau , Naturhistoriska Riksmuseet (Natural History National Museum) ( NHRS), Stockholm, Sweden .

Remarks. Mesovelia horvathi was described by Lundblad (1933) from a set of four syntypes, consisting of a female specimen taken at Lake Ranau in southern Sumatra (the modern Sumatera Selatan Province of Indonesia), and three additional specimens from Java, consisting of a male from Lake Lamongan, and a male and a female from Lake Pakis, both of these being crater lakes lying immediately to the east of Klakah in eastern Java. At the Lake Lamongan locality, the specimen was noted as having been taken amid aquatic plants, whereas at Lake Pakis the specimens were taken from moss.

In the original description, Lundblad compared his species with M. orientalis Kirkaldy, 1901 , i.e., the currently valid Mesovelia vittigera Horváth, 1895 , and mentioned that the legs of both species were very similar, with the difference being that the middle leg in M. horvathi lacked ventral spines. Lundblad's discussion would thus imply that in M. horvathi the fore leg might possess 5–7 ventral spines as in M. vittigera . However, his figures 72 C and D clearly indicate the absence of such spines on both the fore and hind legs ( Lundblad 1933). This confusion about the presence or absence of dark spines, and their number, on the flexor region of the fore femur has not been noted in subsequent work on the genus ( Thirumalai 1989, 1994, J. Polhemus & D. Polhemus 2000, Andersen & Weir 2004, Chen et al. 2006, Yang & Murphy 2011, Chandra & Jehamalar 2011, Jehamalar & Chandra 2016, Basu et al. 2016, 2018).

In the present study, the third author examined three apterous males and two apterous females of M. horvathi from Sumatera Utara and Bengkulu provinces of Sumatra. All of these specimens lack spines on both the fore and mid femora, and conform in all respects to the illustrations of M. horvathi provided by Lundblad (1933). As such, they form the basis for our interpretation of this species. Lundblad did not explicitly designate a holotype for M. horvathi , and no lectotype has been designated to date. Because we have not seen Lundblad's specimens, and therefore cannot evaluate their condition, we defer from doing so here.

A molecular analysis undertaken by Damgaard et al. (2012), which included sequence data from specimens of M. horvathi taken in Australia, New Caledonia, Papua New Guinea, and Laos, indicated a modest degree of sequence divergence among the populations grouped under this species name, and subsequent study may reveal that cryptic species are also present in these regions. In particular, in the analysis of Damgaard et al. (2012), the populations from New Caledonia and New Guinea clustered as a clade sister to those from Laos and Australia. J. Polhemus & D. Polhemus (2000) noted that a similar but undescribed species with a differing male paramere morphology was present on Ceylon, and that populations fitting within the broad species concept were also present in Africa, although they speculated that the latter might eventually prove to represent a separate species. In regard to the populations occurring west of Indochina, these authors concluded that “…the westernmost range of M. horvathi thus remains unclear, pending further analysis of these peripheral populations.”

Our current morphological analysis indicates that many of the populations of the M. horvathi complex present on the Indian subcontinent represent a set of distinct species, as described herein. A more critical morphological assessment of material from Misool and Sumba islands in the eastern Malay Archipelago now indicates that those populations are also distinct from nominate M. horvathi , but this problem will be addressed in a subsequent study. The previous few records of M. horvathi from India by Thirumalai (1989, 1994), Chandra & Jehamalar (2011), Jehamalar & Chandra (2016), and Basu et al. (2016, 2018) may belong to one of the species described here, or other new species. The present study thus suggests that M. horvathi may not have the wide distribution currently ascribed to it, and that previous records of this species from Australia, Borneo, Papua New Guinea, Japan, China, Indonesia, Malaysia, Myanmar, Philippines, Singapore, Taiwan, Cambodia, Thailand and Vietnam by J. Polhemus & D. Polhemus (2000), Damgaard et al. (2012), and D. Polhemus (2017) should be carefully re-examined. We have plotted the distribution of reliably confirmed populations of this species from Java and Sumatra in Fig. 10C . We consider it likely that “true” M. horvathi may eventually be shown to be endemic to the Greater Sunda Islands.

Figures

FIGURES 1A–F. Mesovelia horvathi Lundblad apterous male: A, habitus, dorsal view; B, dorsal view of legs; C, eighth abdominal segment, lateral view; D, genital capsule, dorsal view; E, same, lateral view; F, fore femur, ventral view (dmp—dorsomedian projection of pygophore; lex—lateral excavation; lp—lateral process; pa—paramere; pr—proctiger; py—pygophore).

FIGURES 10. A–B. Mesovelia melanesica Polhemus & Polhemus.A, eighth abdominal segment of apterous male, lateral view; B, genital capsule of apterous male, lateral view; C, Distribution of confirmed populations of Mesovelia horvathi on Sumatra and Java. Data from Lundblad (1933) and subsequent surveys by J. T. and D. A. Polhemus in 1985 and 1991; D and E, fore and mid femora apterous male, ventral view, D, M. dilatata sp. nov., E, M. bispinosa sp. nov.