Hydrometra aequatoriana, Cianferoni, Fabio & Buzzetti, Filippo Maria, 2012

Cianferoni, Fabio & Buzzetti, Filippo Maria, 2012, The genus Hydrometra Latreille in Ecuador with description of a new species (Hemiptera: Heteroptera: Gerromorpha: Hydrometridae), Zootaxa 3274, pp. 55-62 : 56-58

Hydrometra aequatoriana n. sp.

Material examined. ECUADOR: Pichincha, Rio Toachi (residual pools on river shore), La Unión del Toachi, 850 m, 0°18’57”S 78°57’15”O, 22.VI.2009, F. Cianferoni legit, 2 3 macropterous, 1 3 brachypterous. Type depository. 1 3 macropterous (Holotype) in MZUF (collection number 839); 1 3 macropterous (Paratype), CFC; 1 3 brachypterous (Paratype), FMB.

Type locality. Ecuador, Pichincha, Rio Toachi, La Unión del Toachi.

Diagnosis. The male of this species is characterized by a distinct concavity between the VIth and VIIth sternites ( Fig. 1 ), and a peculiar disposition of acetabular pits ( Fig. 2 ): anterior (1 / 1), middle (2 / 2), hind (4), that differs from other species (see Tab. 1 for a comparison with H. adnexa Drake, 1956 ).

Anterior acetabula Middle acetabula Hind acetabula Anterior Posterior Anterior Posterior Anterior H. adnexa 1 1-2 1 1 2-3 H. aequatoriana 1 1 2 (1+1) 2 4

Description. Colour. Dorsal and ventral ground colour light brown (fixed specimens). Body surface with very small black spinules, hardly visible, especially concentrated on distal head swelling and on ventral abdominal surface, absent from the abdominal tergites, which also appear shinier. Long golden hairs present on terminal abdomen. White silver setae forming spots between lateral sides of tergites (depending by illumination). Thin bright setae present on entire body, head, legs and antennae. Pronotum with darker rings and a lighter pit in the centre. Anteclypeus brown, maxillary plates darker. Gular lobe and rostrum translucent. Legs yellowish brown, darker at the distal portion of femora and tibiae. Tarsi brown.

Structure. Overall length: macropterous male 9.1–9.5, brachypterous male 9.0; females unknown.

Head long (2.80–2.95), wider just before antennal tubercles (0.38–0.40). Maxillary plate irregular and slightly hollow. Gular plate rounded, keeping base of rostrum. Rostrum curved reaching about middle of postoculus. Anteoculus to postoculus ratio 1.67–1.73/0.88–0.93. Interoculus shorter than half eye diameter. Anteclypeus triangular with rounded or slightly pointed tip. Antennal article I (0.57), II (0.97).

Prothorax with a row of pits on the anterior lobe, forming collar. Scattered pits on the posterior lobe, forming a longitudinal line in the middle. Pronotum length 1.40–1.57. Distance between coxae I and II: 0.67–0.83, between coxae II and III: 0.97–1.27. Anterior acetabula with one pit on anterior and posterior parts; middle acetabula with two pits on anterior (one is very marginal) and posterior parts; hind acetabula with four pits in the anterior part. Propleuron with one row of 6–7 pits arranged as in illustration ( Fig. 2 ). Proportions of legs: femur, tibia, tarsal I, tarsal II, tarsal III. Fore leg: 4.00–4.20/4.55–4.80/0.07/0.23–0.27/0.17–0.20. Middle leg: 3.00–3.35/3.25–3.50/ 0.07/0.27–0.30/0.17–0.23. Hind leg: 2.95/3.05-3.15/0.07/0.20–0.25/0.20–0.23.

Abdomen length (male): 4.80-5.10. VIIth sternite with long hairs. Sporadic long hairs also on previous sternites. Distinct concavity between VIth and VIIth sternite ( Fig. 1 ).

Male terminalia as in Fig. 1 . Sternite VIII with two tufts of hairs, one on each side.

Distribution. Known only from the type locality. Ecuador, Pichincha, Toachi River.

Etymology. From the Latin adjective for Ecuador.

Comparative notes. Hydrometra adnexa Drake, 1956 from Panama, described on the basis of a single apterous female and to date known only from the type, is apparently quite similar to our male specimens. The arrangement of acetabular pits given for the female of H. adnexa is not so different (considering the variability of this character) from that present in H. aequatoriana n. sp. males ( Tab. 1).

The major difference between the two species is the distribution of black spinules on the body surface: such spinules are present on body surface of H. aequatoriana n. sp. almost exclusively on the distal swelling of the head and the ventral surface of the abdominal segments (especially the last three segments), with scattered spinules on the remaining surfaces, and absent from the dorsal surface. In H. adnexa , by contrast, such spinules are more uniformly distributed and present also on the dorsal body surface, especially on the pronotum. We have examined other New World species of Hydrometra and found these spinules to be present in both sexes of all species, with identical patterns of distribution in both males and females. We therefore separate H. aequatoriana n. sp. from H. adnexa on the basis of the different pattern and extent of black spinules distribution, concluding that our material does not represent the currently undiscovered male of H. adnexa .

Body colour also seems to be helpful in separating New World Hydrometra , because most species have a distinctive colour pattern. In general there are species with dark body colour (e.g. H. caraiba Guérin-Méneville, 1857 , H. williamsi Hungerford & Evans, 1934 and others) and species with light body colour (e.g. H. argentina Berg, 1879 ). The body colour of H. adnexa is dark brown, while in H. aequatoriana n. sp. it is light brown. After the examination of hundreds of specimens belonging to eight species of New World Hydrometra , we conclude that there is little if any intraspecific variability in the ground body colour of Neotropical Hydrometra species. Furthermore, in every species examined there is no difference between male and female body colour. Therefore, the colouration of the body further separates H. aequatoriana n. sp. from H adnexa and reinforces the conclusion that our material can not be the undescribed male of H. adnexa .

Finally, based on our current status of knowledge, the genus Hydrometra in the Neotropical region contains more than thirty species: 15 in Central America and 19 in South America. Only a few species are distributed across the two areas: H. argentina and H. caraiba have a very wide range, while H. comata Torre-Bueno, 1926 , H. guianana Hungerford and Evans, 1934 , Hydrometra thomasi Mychajliw, 1961 and H. zeteki Drake, 1952 seem to be more circumscribed between Central and South America. Considering the New World Hydrometra (39 spp.) as a whole, most of them are distributed in Central America or South America, with only two species present in both Central and South America. The majority of the New World species have distributions restricted to South or Central America, but not both, so we believe that our material represents a new South American species similar to H. adnexa .

Figures

FIGURE 2. Acetabular and propleural pits of H. aequatoriana n. sp. (male). Scale bar 1 mm (drawing F. Cianferoni).

FIGURE 1. A, B. Abdomen of H. aequatoriana n. sp. (male) in lateral (A) and ventral (B) view (photo F. M. Buzzetti).