Bidessus nesioticus Guignot, 1956

Bergsten, Johannes, Ranarilalatiana, Tolotra & Biström, Olof, 2020, A new species of Bidessus from Anjozorobe-Angavo and a review of Malagasy Bidessus (Coleoptera, Dytiscidae), European Journal of Taxonomy 720, pp. 1-18 : 13-14

Bidessus nesioticus Guignot, 1956

Figs 2A , 3E

Bidessus nesioticus Guignot, 1956: 77 .

Bidessus nesioticus – Bistr̂m 1985: 35. — Rocchi 1991: 85. — Nilsson 2001: 115. — Nilsson & Hajek 2020: 104.

Diagnostic characters

Head frontally not margined; somewhat posterior to frontal edge (between eyes) with a transverse depression which becomes indistinct medially. Pronotum on disc with a quite broad, almost impunctate area (fine scattered punctures discernible). Pronotal striae quite deeply impressed, distinctly angled (striae not smoothly curved). Basal striae of elytra moderately long, not deeply impressed. Sutural lines distinct; posteriorly they fade away a short distance before apex; anteriorly, distinguished almost up to posterior edge of pronotum. Size of punctures on each side of basal striae rather fine, almost of equal size. Apical ventrite with fine, quite sparse punctures. Female with posterior outline of elytra smooth (no minor extension). Penis, dorsal aspect comparatively broad and short; in lateral aspect curved. Apex of penis not distinctly extended ( Fig. 3E ).

Body length 1.6–1.7 mm. Shiny, dorsally not microsculptured (frontally on head fragments of reticulation distinguished). General color of body dark piceous to blackish. Pronotum discally on each side with a well-delimited, testaceous spot. Elytra with vague, slightly paler, longitudinal markings. Apex of elytra slightly paler. Base of antenna and legs in part slightly paler.

Material examined

Holotype

MADAGASCAR • 1 ♂; Ankaratra , Tsiafajavona; 2500 m a.s.l.; Jun. 1947; J. Millot leg.; MNHN. [Note that Bistr̂m (1985) during his revision of the group, was unable to locate this holotype that we have since rediscovered.]

Additional material

MADAGASCAR • 1 spec.; Antananarivo former province, Vakinankaratra region, Manjakatompo Stn Forestière, Anosiarivo ; 19.34489° S, 047.30414° E; 2073 m a.s.l.; 24 Jan. 2012; T. Ranarilalatiana and J.H. Randriamihaja leg.; collecting event MAD-MJK12-13; lake near source; NHRS-JLKB000025031 • 20 specs (preserved in ethanol); same collection data as for preceding; NHRS-JLKB000024967 • 5 specs; same collection data as for preceding; FMNH • 5 specs; same collection data as for preceding; PBZT / MBC • 5 specs; same collection data as for preceding; BMNH • 5 specs; same collection data as for preceding; DEUA • 18 specs (preserved in ethanol); Fianarantsoa former province, Haute Matsiatra region, Andringitra NP, lake north east of camp 3; 22.17373° S, 46.9016° E; 2026 m a.s.l.; 2 Dec. 2013; J.H. Randriamihaja and T. Ranarilalatiana leg.; collecting event MAD13-33; small lake in open area; NHRS-JLKB000025023 • 5 specs; same collection data as for preceding; PBZT / MBC • 4 specs; Fianarantsoa former province, Ankaratra massif, ca 2.7 km WNW of Manjakatompo; 19°21′57″ S, 47°18′22.5″ E; 1814 m a.s.l.; 19 Dec. 2017; Ramahandrison and Manuel leg.; large grassy temporary pond, beneath slope with pine trees, with Conchostraca crustaceans; CMM .

Distribution

Endemic species to Madagascar and known from the Ankaratra and Andringitra mountain massifs in central Madagascar ( Fig. 4C ).

Collecting circumstances

This is a high-elevation alpine species on Madagascar, only known from above 1800 m altitude. The type material was collected at 2500 m altitude near the Ankaratra peak Tsiafajavona in 1947. TR and Jacquelin Herisahala Randriamihaja found it in an overflooded glade near a source in 2012 at a slightly lower elevation on Ankaratra (2073 m) ( Fig. 6A ). Additionally, they discovered the species for the first time outside Ankaratra in a small lake with vegetation at 2026 m elevation in Andringitra NP further south in 2013 ( Fig. 6B ). A few specimens were collected in a clearwater grassy pond as low as 1814 m in the Ankaratra mountain by A.T. Ramahandrison and M. Manuel in 2017.

Figures

Fig. 2. Habitus photographs of Malagasy species of Bidessus Sharp, 1882. A. B. nesioticus Guignot, 1956 (NHRS-JLKB000025031). B. B. perexiguus Kolbe, 1883 (NHRS-JLKB000025029). C. B. longistriga Régimbart, 1895 (NHRS-JLKB000025028).

Fig. 3. Male genitalia of the Malagasy species of Bidessus Sharp, 1882. For each subpanel from left to right penis in dorsal view, penis in lateral view and paramere in lateral view. A. B. apicidens Bistr̂m & Sanfilippo, 1986. B. B. cf. ceratus Guignot, 1941. C. B. anjozorobe sp. nov. D. B. cf. nero Gschwendtner, 1933. E. B. nesioticus Guignot, 1956. F. B. perexiguus Kolbe, 1883. G. B. longistriga Régimbart, 1895.

Fig. 4. Distribution maps of the Malagasy species of Bidessus Sharp, 1882. A. B. longistriga Régimbart, 1895. B. B. perexiguus Kolbe, 1883. C. B. cf. nero Gschwendtner, 1933 (circle), B. nesioticus Guignot, 1956 (square), B. anjozorobe sp. nov. (triangle). D. B. apicidens Biström & Sanfilippo, 1986 (square), B. cf. ceratus Guignot, 1941 (circle).

Fig. 6. Two localities of the high-altitude alpine species Bidessus nesioticus Guignot, 1956 previously known but from the type locality at 2500 m a.s.l. near the peak Tsiafajavona of Ankaratra mountain. A. A glade swamped by water from a source [MAD-MJK12-13] in Manjakatompo Ankaratra, 2070 m a.s.l. B. The new location [MAD13-33] of Bidessus nesioticus Guignot, 1956 at a pond in the alpine zone 2030 m a.s.l. on the Andringitra mountain massif in Andringitra NP.