Agabus ramblae, Millan & Ribera, 2001

Millán, Andrés & Ribera, Ignacio, 2001, The Agabus (Gaurodytes) Brunneus Group, With Description Of A New Species From The Western Mediterranean (Coleoptera: Dytiscidae), The Coleopterists Bulletin 55 (1), pp. 107-112 : 109-111

Agabus ramblae , new species

Type Series. Holotype. Male (The Natural History Museum, London, NHM): ‘‘SPAIN Murcia /rambla de Malvariche 30SXG29/ 2.3.1981 Suárez & Vidal leg.’’ Paratypes. 1 male, same data as holotype ; 3 males and 3 females, Fuente Zarzadilla (U. T.M. grid square 30SXG19), 4.3.1980 Suárez & Vidal leg. ; 1 male, river Mula, Puebla de Mula (30SXH31), 12.8.1980 Suárez & Vidal leg. ; 2 males and 2 females, rambla de Malvariche, Los Chorrillos (30SXG29), 20.5.1981 Suárez & Vidal leg. ; 1 female, Junta de Ramblas in Casas Nuevas (30SXG29), 20.5.1981 Suárez & Vidal leg. ; 1 male, rambla in El Salar de Blanca (30SXH42), 22.2.1989 A. Millán leg. ; 1 male, rambla Caputa (30SXH31), 15.5.1990 A. Millán leg. ; 1 male, rambla del Judío, Cieza (30SXH33), 1.7.1990 A. Millán leg. (The Natural History Museum, London; Museo Nacional de Ciencias Naturales, Madrid; Naturhistorisches Museum, Wien,; coll. H. Fery, Berlin; coll. X. Fresneda, Lleida; coll. A. Nilsson, Umea ˚; coll. G. Foster, Ayr; coll. R. Angus, London ; coll. A. Millán, Murcia, coll. I. Ribera, Barcelona) .

Etymology. Named after ‘‘rambla’’ (female), the local name of the temporary streams in which the species is typically found in the SE of the Iberian peninsula.

Description. Total length: 6.3–8.0 mm; maximum width 3.8–4.8 mm. Head of most specimens uniformly ferrugineus, at most a diffuse darker area in the crown; dorsal surface and appendages rufous. Ventral surface black, except underside of the pronotum and edge of the last four abdominal sterna rufous. Head densely microreticulated. Pronotum with a rather broad lateral bead, well delimited and of uniform width; irregular and densely microreticulated; sparsely punctured. Elytra with several irregular rows of larger punctures. Prosternal process lanceolate, flat, finely bordered. Ventral surface shiny; metacoxal plates finely microreticulated, meshes larger than those of the elytra. Sterna with fine longitudinal lines. Metafemora and metatibiae with strioles, metatibiae with two long spurs, longer than half the length of the tibia. Membranous wings well developed.

Karyotype. Specimens from Huesca had 43 chromosomal pairs, an habitual number in the species of Agabus , with an XO system of sex determination (R. B. Angus pers. comm., 1995).

Sexual Dimorphism. Male with protarsomeres slightly dilated; protarsal claws equal in size, smoothly and regularly curved. Aedeagus regularly curved in lateral view, with the maximum width shortly before the apex ( Fig. 5 ); very narrow in dorsal view, asymmetrical, with the apex slightly curved to the left ( Fig. 6 ). Males and females do not differ significantly in size (as compared with a two­tailed t ­student, Table 1).

Variation. Color varied from pale yellowish­red to dark brown. Some specimens have a dark spot on the head, although without a defined shape (see above). No variation was found in the size or shape of the aedeagus. See Table 1 for size variation.

Distribution. The species is widely distributed in the East of the Iberian peninsula, in the provinces of Albacete (Agramón, 21.9.1997, Ribera leg.; Robledo, Ojos de Villaverde, 7.9.1997 Ribera leg.; Paterna del Madera, 6.9.1997, Ribera & Aguilera leg.; Pétrola, 23.5.1998, Millán et col. leg.; Pinilla, 32.10.1998, Millán & Moreno leg.; El Salobralejo 29.5.1999, Millán et col. leg.); Almería, Castellón (Matet, 11.9.1997, Ribera & Millán leg.); Ciudad Real (Lagunas de Ruidera, río Ossero, 30.5.1999, Millán et col. leg.); Huesca, Jaén, Murcia (Lorca, rambla del Estrecho, 5.8.1999, Perán leg.); Teruel; Valencia; Zaragoza; and the Balearic Islands (Mallorca and Menorca) (only details of localities not included in Millán et al. 1997 are given).

Biology. Agabus ramble is typically found in small streams or rivers (‘‘ramblas’’ in Murcia, ‘‘torrents’’ in the Balearic islands, or ‘‘barrancos’’ in Huesca and Zaragoza), often temporary, with mineralized waters (calcareous, 0.5–3.0 gr./l. of dissolved salts in the type locality), silt or clay substratum, and sparse riparian vegetation. Altitude ranged from sea level to approximately 1,300 m a.s.l. The specimens were mainly collected in shallow areas with a slow water flow, usually clean and well oxygenated, although in the Segura basin the species was found in some eutrophic waters. In some permanent rivers, as well as in the northernmost point of its known distribution (province of Huesca), the species coexisted with A. brunneus , although in its more characteristic habitats (mineralized ‘‘ramblas’’ and ‘‘barrancos’’) A. brunneus is usually not found. In Menorca (Balearic Islands) the species coexisted with A. brunneus in most of the sites. The species seems to be a spring or summer breeder, overwintering as adult, although more data are needed to establish its life cycle with certainty.

Figures

Figs. 1–6. Aedeagus of Agabus brunneus 1) lateral view; 2) dorsal view; A. rufulus 3) lateral view; 4) dorsal view; and A. ramblae 5) lateral view; 6) dorsal view; (traced from photographs).