Bidessus cf. nero Gschwendtner, 1933,

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: 11-13

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Bidessus cf. nero Gschwendtner, 1933


Bidessus cf. nero Gschwendtner, 1933 

Figs 1DView Fig, 3DView Fig

Bidessus nero Gschwendtner, 1933: 86  .

Bidessus nero  – Bistr̂m 1985: 18. — Nilsson 2001: 115. — Nilsson & Hajek 2020: 104.

Bidessus unicolor (Guignot, 1946)  – Guignot 1959: 255.

Diagnostic characters

Head frontally not margined; provided with a slight depression slightly posterior to anterior edge of head (between eyes); frontal depression is medially broadly vague and indistinct. Pronotum on disc with a broad impunctate area. Pronotal striae at base not deeply impressed, distinctly angled and not smoothly curved. Basal striae of elytra medium long and distinct. Anteriorly sutural lines of elytra disappear abruptly a short distance before reaching frontal edge; posteriorly lines fade away long before reaching apex. Elytra with punctures on each side of basal striae of equal size and density (rather fine, sparse and slightly irregular). Apical ventrite with rather fine, slightly sparse punctuation. Female with outline of elytra posteriorly smooth (minor process absent). Penis in lateral view quite slender and evenly curved; apex distinct (also slightly curved). Penis apex not distinctly extended ( Fig. 3DView Fig).

Length of body 1.5–1.9 mm.

Material examined

MADAGASCAR • 1 ♂; Fianarantsoa former province, Amoron’i Mania region , 3 km south of Ambalamanakana next to RN7, Ankazomivady forest ; 20.7722° S, 47.1809° E; 1700 m a.s.l.; 1 Nov. 2014; J. Bergsten, T. Ranarilalatiana and S.Holmgren leg.; collecting event MAD14-02; hygropetric rocks and marsh with vegetation; NHRS-JLKB000025032GoogleMaps  5 specs (preserved in ethanol); same collection data as for preceding; NHRS-JLKB000025024GoogleMaps  1 spec.; same collection data as for preceding; FMNHGoogleMaps  1 spec.; same collection data as for preceding; PBZT / MBCGoogleMaps  1 spec. (preserved in ethanol); Fianarantsoa former province, Matsiara Ambony region , Ranomafana NP, 500 m from the road at Vohiparara village; 21.2397° S, 47.3774° E; 1110 m a.s.l.; 3 Nov. 2014; J. Bergsten, T. Ranarilalatiana and S. Holmgren leg.; collecting event MAD14-10; small forest lake with floating margins of vegetation; NHRS- JLKB000025025GoogleMaps  1 spec.; Toamasina former province, Alaotra Mangoro region , 6 km W of Moramanga, Betsabora river by RN2 near Antsampanana village; 18.9247° S, 48.1828° E; 900 m a.s.l.; 24 Nov. 2014; J. Bergsten, J.H. Randriamihaja and T. Ranarilalatiana leg.; collecting event MAD14-81; river with side pools; NHRS-JLKB000025026GoogleMaps  2 specs; Fianarantsoa former province, ca 9 km SW Ivato, Bemanta (inselberg); 20°40′00″ S, 47°07′41.5″ E; 1531 m a.s.l.; 18 May 2016; Ramahandrison and Manuel leg.; wide and calm portion of small river; CMMGoogleMaps  16 specs; Fianarantsoa former province, along road N7 between Ambositra and Fianarantsoa, ca 3.5 km S of Ambalamanakana; 20°46′33″ S, 47°10′53″ E; 1702 m a.s.l.; 19 May 2016; Ramahandrison and Manuel leg.; large pond with Nymphaeaceae  and surrounding peat bog with Sphagnum  and Drosera  ; CMMGoogleMaps  13 specs; Fianarantsoa former province, ca 8 km WNW of Ranomafana, ca 1 km SW of Vohiparara; 21°14′51″ S, 47°22′34.5″ E; 1134 m a.s.l.; 29 Dec. 2017; Ramahandrison and Manuel leg.; small marsh, very shallow, with small Poaceae  and Cyperaceae  , along slowly flowing stream; CMM.GoogleMaps 


First record from Madagascar and here recorded from Ranomafana NP, near Ambalamanakana and Ivato along RN7 and near Moramanga ( Fig. 4CView Fig). As tentatively defined here, the species is distributed in central and east Africa and Madagascar (see Bistr̂m 1985; Nilsson & Hajek 2020).

Collecting circumstances

On Madagascar found at elevations between 900–1700 m a.s.l. The localities are characterized by being vegetation-rich stagnant waters, a pool next to a river, a pond/marsh and small lake with floating vegetation edges. Semi-open to open landscapes.

Taxonomic observation

Further study on molecular level may reveal that B. cf. nero  in Madagascar is in fact a separate species.


USA, Illinois, Chicago, Field Museum of Natural History (also used by Finnish Museum of Natural History)


Madagascar, Antananarivo, Parc Botanique et Zoologique de Tsimbazaza


Field Museum of Natural History


Parc Botanique et Zoologique de Tsimbazaza


Montgomery Botanical Center


Culture Collection of Phytopathogenic Fungi (Colecao de Culturas de Fungos Fitopatogenicos Prof. Maria Menezes)














Bidessus cf. nero Gschwendtner, 1933

Bergsten, Johannes, Ranarilalatiana, Tolotra & Biström, Olof 2020

Bidessus nero

Gschwendtner L. 1933: 86

Bidessus nero

Nilsson A. N. & Hajek J. 2020: 104
Nilsson A. N. 2001: 115

Bidessus unicolor (Guignot, 1946)

Guignot F. 1959: 255