Bidessus perexiguus Kolbe, 1883

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 : 15-16

Bidessus perexiguus Kolbe, 1883

Figs 2B , 3F

Bidessus perexiguus Kolbe, 1883: 407 .

Bidessus perexiguus – Régimbart 1895: 82. — Alluaud 1900: 60. — Zimmermann 1920: 56. — Guignot 1959: 260. — Bistr̂m 1985: 28. — Rocchi 1991: 85. — Nilsson 2001: 115. — Pederzani & Rocchi 2009: 93. — Nilsson & Hajek 2020: 105.

Diagnostic characters

Head frontally not margined but provided with a shallow, transverse depression which medially is indistinct. Pronotum discally with a broad area with fine and sparse punctures; distinctly sparser than punctures at frontal and posterior edge. Pronotal striae at base deeply impressed. Pronotal striae with a distinct angle (not smoothly curved). Basal striae of elytra rather short. Sutural lines distinct; anteriorly and posteriorly lines fade away; anteriorly lines transformed to a short row of a few punctures. Punctures on both side of basal striae fine, sparse and of equal size. Apical ventrite with a few fine, slightly irregular punctures. Female with outline of elytra posteriorly smooth (minor extension absent). Penis in lateral view slender, almost evenly curved. Penis apex slightly extended ( Fig. 3F ).

Length of body 1.4–1.5 mm.

Material examined

478 specimens ( NHRS, CAS, NMW, PBZT / MBC, BMNH, DEUA) from provinces Antsiranana, Mahajanga, Toliara and Fianarantsoa (see Supplementary File 1).

Distribution

Endemic species to Madagascar but as B. longistriga widely distributed on the island in lowland areas below 800 m a.s.l. ( Fig. 4B ).

Collecting circumstances

An apt flier that can be collected at light. At low altitude it can occur in a variety of mainly stagnant habitats such as eutrophied ponds, pools in dried out riverbeds, even water-filled wheel tracks. Often occurs sympatrically with B. longistriga , at least in western parts of Madagascar.

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).