Eurymetra madagascariensis Poisson, 1945

Zettel, Herbert, 2020, New water strider species of Eurymetra from Madagascar (Hemiptera: Heteroptera: Gerridae), Acta Entomologica Musei Nationalis Pragae 60 (1), pp. 15-22 : 17-19

Eurymetra madagascariensis Poisson, 1945

(Figs 4, 5, 10)

Eurymetra madagascariensis Poisson, 1945: 89 . SYNTYPES: apterous females, coll. Muséum national d’Histoire naturelle, Paris (not examined): “ Madagascar (Sicard 1930)” [no exact locality given].

Material examined (all in NHMW): 2 (apterous), Madagascar, Antsiranana Province,Nosy Be (Nossi-Bé) Island, Djabalahely, Ruisseau de Djabala, 22.viii.1958, leg. E. Pomeisl (191); 1 1 ♀ (apterous), Madagascar, Antsiranana Province,Nosy Be (Nossi-Bé) Island,Androadroatra, Ruisseau d’Androadroatro, 23.viii.1958, leg. F. Starmühlner ( FM 175).

Redescription. Male. Measurements of non-type specimens (n = 3): BL 3.70–3.90; BW 2.62–2.81; HW 1.42–1.49; IO 0.48–0.51; PW 1.22–1.27; PHI 85–87; TiL 1.68–1.90; TaL 0.50–0.52; TTI 27–30.

Structural characteristics. Eyes large, posteriorly surpassing sides of pronotum; their minimum distance on average intermediate compared to other species. Antennomere 1 with row of ca. 2–5 short oblique setae. Pronotum small, in dorsal view of specimen, as long as half of head length along midline. Apical process of protibia short, slender and weakly curved. Shiny areas of dorsum expand- ed: middle of pronotum and indistinct paired patches on mesonotum weakly shiny; metacetabulum with shiny area on medial half (indistinct in one specimen); metanotum and tergites 1–4 strongly shiny, almost reaching sides of most plates. Sutures between metanotum and tergites 1–3 visible, accentuated by narrow matt stripes. Paramere very narrow all over its length, weakly bent at midlength, distal part moderately narrowed ( Fig. 10 ).

Colour. Yellow marks comparatively small (Figs 4). On head, anterior mark between antennal tubercles orange and more or less interrupted in middle. Paired marks on pronotum narrow, medially only slightly widened anteriorly, narrower than half-length of pronotum. Paired marks on mesonotum subtriangular, large, medially with straight parallel-sided margins. Paired marks on metanotum widely distant from each other. Metapleuron above spiracle with distinct yellow spot. Mark on metacetabulum either small, or larger and medioposteriorly extended. On abdomen, small yellow marks on tergites 6–7, and on laterotergites 6–7 (in one male 4–7). Body ventrally entirely yellow (except metasternum more or less infuscate).

Female (see also “Comparative notes” for syntypes): Measurements of non-type specimen: BL 3.70; BW 2.70; HW 1.42; IO 0.48; PW 1.25; PHI 88; TiL 1.57; TaL 0.49; TTI 31.

Structural characteristics. Similar to male. Apical process of protibia slender and straight. Shiny areas even more developed than in male: in addition, a large medial portion of pronotum and almost the entire mesonotum (except sides) shiny; metanotum and tergites 1–3 fused, without matt stripes indicating sutures, shiny area only interrupted by velvety patch.

Colour. Similar to male (Fig. 5). On head, anterior mark between antennal tubercles interrupted in middle. Metapleuron above spiracle with yellow spot. Mark on metacetabulum moderate in size and medioposteriorly extended (in syntype large, fide POISSON 1945: fig. 3a). On abdomen, very small yellow marks on tergites 7–8 (in syntype 6–8, fide POISSON 1945: fig. 3a), and (slightly larg- er) on laterotergites 6–7. Body ventrally entirely yellow, except metanotum strongly infuscated in middle.

Comparative notes. See key and comparative notes for other species. The conspecificity of the studied material with the syntypes, two females only, remains uncertain, although Raymond Poisson himself identified the four specimens as E. madagascariensis . The species identity is preliminarily fixed on three characters: i) the distinct lateral spot on the metapleuron, ii) the short protarsi, and iii) the normal-sized pronotum (in comparison to the small pronotum of E. santamariae sp. nov.). On the other hand, the syntypes are reportedly larger than the specimens in the Natural History Museum Vienna (BL 4.25–4.5 mm, according to POISSON 1945) and there are also some differences in colour pattern. For example, according to POISSON (1945: fig. 3a) the mark on the metacetabulum is distinctly larger, and tergite 6 possesses a small yellow mark in the middle. Although the variation of colouration cannot be properly evaluated based on only two females, it cannot be excluded that the studied specimens do not represent E. madagascariensis , but a further undescribed species. Geographic conclusions cannot be properly drawn, since the type locality of E. madagascariensis is not specific.

Acta Entomologica Musei Nationalis Pragae, volume 60, number 1, 2020 19

However, it is known that in 1930 A. Sicard (year of collecting and collector of the types; see POISSON 1945) visited the northern mainland of Madagascar, not very distant from Nosy Be Island; see, e.g., CONSTANT 2014).

Figures

Figs 10–12. Left paramere (lateral aspect): 10 – Eurymetra madagascariensis Poisson, 1945; 11 – E. santamariae sp. nov.; 12 – E. papaceki sp. nov.