Hydrometra brevitarsus, Zettel & Yang, 2004

Zettel, Herbert & Yang, Chang Man, 2004, New Oriental Species And Subspecies Of Hydrometra Latreille (Heteroptera: Hydrometridae), Raffles Bulletin of Zoology 52 (2), pp. 389-398 : 389-391

Hydrometra brevitarsus , new species

( Figs. 1-5 )

Hydrometra papuana Kirkaldy, 1901 : Polhemus & Polhemus, 1995: 40-41 (part, misidentification).

Material examined. – Holotype - (apterous male): SINGAPORE, MacRitchie Forest , “G” stream, 20 Apr.1994, coll. K. L. Yeo ( ZRC).

Paratypes – (all apterous): 1 female (allotype): Singapore, Lorong Banir, outflow stream from Nee Soon swamp forest ( ZRC) . WEST MALAYSIA: Johore: 1 female, Sg. Temantang, coll. H. K. Lua, 24 Feb.1995 ( ZRC) ; Pahang: 1 male, Kuantan, 15 May.1995 ( ZRC) ; Perak: 2 females, Taiping, nr. Bt. Merah, coll. H. H. Tan, 18 Nov.1995 ( ZRC) ; EAST MALAYSIA: Sarawak: 1 male, 2 females, Kuching-Sri Aman Rd. , nr. Simunjan, coll. H. H. Tan & S. H. Tan, 4 Sep.1996 ( SKM, ZRC) ; INDONESIA: Pulau Batam : 1 female, 29 Jan.1992 ( ZRC) ; Sumatra: 8 males, 10 females, Jambi, Darkie Water Reserve , 6 Jun.1996 ( MZB, ZRC, NHMW) .

Description of holotype, apterous male. – Body length 13.9 mm (range 13.9 – 15.7 mm, n = 11), head length 4.3 mm, head width at eyes 0.50 mm, width at metacetabula 0.68 mm, length of antennomere 2: 2.1 mm, length of mesotibia 7.1 mm.

Colour: mainly orange brown, head ventrolaterally and between eyes, ventral and lateral parts of abdomen, and terminalia dorsally darker brown; mediotergites and laterotergites yellowish brown; connexiva black; pads on sternite 7 black; antennae yellowish brown, darker towards apex; legs yellowish brown, coxae and trochanters yellow, apices of femora, tibiae and tarsi dark brown to blackish; sides of thorax and abdomen with continuous whitish stripe.

Structural characteristics: head very long, slightly wider at eyes than at antennal tubercles (1.05 times), AO 3.0 times as long as PO; anteclypeus only slightly shorter than wide (0.85 times), with sides convex, anterior margin nearly straight, but dorsal surface distinctly depressed anteromedially, thus appearing bilobed dorsally with concave anterior margin in dorsal view ( Fig. 1 ), surface smooth and shining; maxillary plate narrow, elongate, with concave ventral margin, hardly covering base of gular lobe laterally. Minimum dorsal distance between eyes 0.65 times of eye width; rostrum in resting position slightly surpassing posterior margin of eye; relative lengths of antennomeres ca. 0.4: 1.0: 2.4: 0.9.

Pronotum 0.45 times head length; metanotum 0.4 times head length. Pronotum with few pits anteriorly weakly delimiting collar, and scattered over pronotal lobe, but no pits on acetabula; wing rudiments not visible; distance between mes- and metacetabula 2.0 times that between pro- and mesacetabula. Relative lengths of leg segments (in relative to mesotibia = 100): profemur – 75, protibia – 83, protarsus – 1+4+3, mesofemur – 86, mesotibia – 100, mesotarsus – 1+5+4, metafemur – 101, metatibia – 127; metatarsus – 1+5+3; ratio of mesotarsus: mesotibia – 10.4 (range 10.3 – 11.7, n = 12); second mesotarsomere 1.6 times as long as third.

Abdomen relatively short and narrow, 1.6 times as long as thorax along dorsal midline; fifth tergite 5.5 times as long as wide; tergite 7 posteriorly 1.4 times as wide as anterior margin, with most of surface convex except anteriorly; connexival corner rectangular, without prominent pilosity; sternite 7 ventrolaterally bearing pair of prominent pads with closely set, appressed black setae, posterior end of pad flaplike and raised from surface of sternite; length of pad 0.65 times length of sternite, pads ventrally separated by more than their width anteriorly, but slightly less than their width posteriorly; segment 8 relatively small, about as wide as segment 7 posteriorly in dorsal view, with rounded posterior corners, short triangular distal process dorsomedially, ventromedian carina with shallow ventrolateral depressions ( Figs. 4, 5 ).

Description of allotype, apterous female. – Similar to holotype but slightly longer. Body length 15.9 mm (range 15.9 – 18.0 mm, n = 16), head length 4.7 mm, head width at eyes 0.51 mm, width at metacetabula 0.79 mm, length of antennomere 2: 2.1 mm, length of mesotibia 6.9 mm.

Structural characteristics: AO 3.3 times as long as PO; metanotum 0.35 times of head length; distance between mes- and metacetabula 2.0 times that between pro- and mesacetabula; relative lengths of leg segments (relative to mesotibia = 100): profemur – 78, protibia – 87, protarsus – 1+5+3, mesofemur – 87, mesotibia – 100, mesotarsus – 1+6+4, metafemur – 105, metatibia – 126; metatarsus – 1+5+4; ratio of mesotarsus: mesotibia – 9.5 (range 9.1 – 10.3, n = 18); second mesotarsomere 1.5 times as long as third.

Abdomen relatively short and narrow, almost straight, 1.8 times as long as thorax along dorsal midline; sternites 5 and 6 each with rows of several long setae located at connexival margin in medial third of length; sternite 7 with 0 – 3 setae at connexival margin (except in one aberrant female from Kalimantan with 10 setae on right side and 2 setae on left side); fifth tergite 6.5 times as long as wide; posterior margin of tergite 7 1.3 times as wide as anterior margin, most of posterior surface convex; tergite 8 truncate, without distal spine, leaving proctiger uncovered; sternite 7 protruding caudad, and covering gonocoxae ventrally ( Figs. 2, 3 ).

Macropterous morph. – Not available for study.

Remarks. – Hydrometra brevitarsus , new species, is an Oriental sibling species of the Papuan-Australian H. papuana . The latter has been recently redescribed by Polhemus & Lansbury (1997) based on a newly designated neotype from Western Province, Papua New Guinea. Polhemus & Polhemus (1995) and Polhemus & Lansbury (1997) regard H. papuana as a species widely distributed from the Malay Peninsula to the Solomon Islands. The type material of H. brevitarsus new species clearly differs from the description of H. papuana in Polhemus & Lansbury (1997) and from Australian specimens studied by the present authors: The anteclypeus is short in H. papuana , but relatively longer in H. brevitarsus . The pad on male sternite 7 is short in H. papuana , but longer in H. brevitarsus . The female connexivum 7 has several long setae (ca. 4 – 8) in H. papuana , but is either without setae or with a reduced number (1 – 3) of setae in H. brevitarsus (1 female from Kalimantan is aberrant, bearing 10 setae on the right side and 2 on the left side). The two species can be easily distinguished by the relative lengths of mesotibia to mesotarsus. This ratio is 10.3 – 11.7 in males (n = 12) and 9.1 – 10.3 in females (n = 18) of H. brevitarsus , but in studied specimens of H. papuana from Australia is 6.9 – 7.0 in males (n = 3), 5.9 – 6.9 in females (n = 4); 6.9 in the male described by Polhemus & Lansbury (1997); and with following ratios in further specimens measured by I. Lansbury (pers. comm.): in specimens from Australia 6.2 – 7.0 in males (n = 3), 6.5 – 7.0 in females (n = 4); in one male from western New Guinea 7.4; in one male and one female from Solomon Islands 5.9 and 6.1, respectively. All measurements combined, the ranges of mesotibia to mesotarsus length ratios are 9.1 – 11.7 in H. brevitarsus (n = 30), but 5.9 – 7.4 in H. papuana (n = 18). There is also a difference in size, H. brevitarsus being larger than H. papuana (with overlapping ranges in females): the body length of 13.44 – 17.12 mm in males, 16.48 – 18.56 mm in females from Borneo and West Malaysia (= H. brevitarsis) (Polhemus & Polhemus 1995) which agrees well with our measurements presented here 13.9 – 15.7 mm in males and 15.9 – 18.0 mm in females. The body length of H. papuana from Australia, New Guinea, and Solomon Islands given by Polhemus & Lansbury (1997) were 11.93 – 13.18 mm for males, and 13.76 – 18.09 mm for females.

Distribution. – West Malaysia, Singapore, Sumatra, Borneo ( Fig. 17).

Ecological Notes. – This species occurs in small numbers in pools or margins of streams in lowland swampy forests and peat swamp forests where the pH is below 5.0. This species is one of the larger Hydrometra in the region. It sometimes co-exists with H. carinata Polhemus & Polhemus, 1995 or H. longicapitis Torre-Bueno, 1927.

Etymology. – Named after the most conspicuous character, the short tarsi.

Figures

Figs. 1-5. Hydrometra brevitarsus, new species. 1, head, dorsal view showing anteclypeus; 2, female terminal abdomen, dorsal view; 3, female terminal abdomen, lateral view; 4, male terminal abdomen, ventral view; 5, male terminal abdomen, lateral view.