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

The Eurymetra madagascariensis species group

Diagnosis. Body stout, size small to moderate, BL 3.7–4.8, BW 2.62–3.40. Dorsum relatively dark coloured, pattern as in Figures 4–9; head with large black patch between eyes; on antenna, only base of antennomere 1 yellow; mesopleura with wide, completely isolated, black stripe; tergites 1–4 (often also 5) black, without yellow marks. Eye very large, posteriorly reaching or surpassing anterior margin of mesopleuron. Antenna long, very slen- der and unmodified in both sexes; antennomere 1 with a row of short setae ( Fig. 1 ). Pronotum small, lateral margins embraced by eyes. Metasternal scent gland opening situated on a low round tubercle ( Fig. 3 ). Fore leg of male hardly modified, but longer than in female; erect pilosity on flexor side of femur slightly denser; apical process on tibia slightly more curved. Genitalia of male very small, simple and uniform: Pygophore squared, apically truncated, ca. 1.2 times as long as wide; proctiger elongated, slightly surpassing pygophore, including basal processes ca. 1.6 times as long as wide, with evenly rounded apex; paramere small, more or less upcurved, without setae, with narrowly rounded apex ( Figs 10–12 ). Tergite 1 of female with large patch of velvety dark pilosity ( Fig. 2 ). Sternite 7 of female short and truncated; gonocoxa 1 exposed.

Comparative notes. The distinct patch of velvety pilosity on tergites 1–2 of females, first described by POISSON (1945, as “tache «scutellaire» noir mat”), is unknown from other halobatine water striders. The type species of Eurymetra , E. natalensis (Distant, 1903), and three obviously closely related forms, E. angolensis Hoberlandt, 1951, E. nitidula ( Esaki, 1926), and E. pauliani Poisson, 1941 clearly differ by their rich yellow colouration, large size (BL> 5 mm, except for E. nitidula), and comparatively small eyes; their metasternal scent gland opening is not distinctly elevated (this character remains undescribed for E. pauliani and E. nitidula). Two smaller, poorly known species from Africa, E. aethiops (Distant, 1903) and E. africana Poisson, 1947 are more similar in colour pattern to the E. madagascariensis group, but they do not possess a velvety patch in females, either.

Diversity and distribution. At present three species endemic to Madagascar are known. It is expected that more species will be discovered when material from other parts of the island becomes available.

Figures

Figs 1–3. Diagnostic characters of the Eurymetra madagascariensis species group (images of E. papaceki sp. nov.): 1 – first antennomere of left antenna of a male, illustrating the sparsely distributed setae; 2 – abdomen of a female in slightly oblique dorsal view, illustrating the velvety patch; 3 – thorax (in part) and abdomen of a female in ventral view, illustrating the roundish elevation of metasternal scent gland opening and exposed gonocoxae 1. Abbreviations: mtn – metanotum; t1–t8 – tergites 1–8; vp – velvety patch.

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