Cylindrostethus meloi Floriano and Cavichioli

Floriano, Carla Fernanda Burguez & Cavichioli, Rodney Ramiro, 2013, A new species of Cylindrostethus Mayr (Hemiptera, Gerromorpha, Gerridae) for the Neotropical Region, with an identification key for the species of Group 1 sensu Drake 1952, Zootaxa 3702 (2), pp. 187-192 : 188-190

Cylindrostethus meloi Floriano and Cavichioli , sp. nov.

Figs 1–9

Type Material: Brazil, Amazonas. Holotype (male) “ Brasil: Amazonas\ Ig. (Igarapé) Boiaçuzinho\ R. (Rio) Demeni – R. (Rio) Negro\ 5–X–1977. Dellone” “ C. erythropus – Inpa” [ INPA]. Paratypes. 4 males and 8 females, same data as the Holotype, 1 male and 1 female [ DZUP], all other [ INPA]. 1 female and 1 male “BR ( Brasil) – AM (Amazonas), Barcelos, Rio\ Acará\ 29–VII–2009 \ PT 1006”; 1 male and 4 females “BR ( Brasil) – AM (Amazonas) R. (Rio) Solimões\ Jutaí (igarapé afluente \ do rio Sapó” “2,76119º – 66,79997º\ 06–IX–2003 \ N.Hamada & J. L. Nessimian” “2062” [ INPA].

Diagnosis. Generally dark brown; rostral segments I and II yellow, III dark; pronotum with yellow median furrow; anterodorsal region of fore femora with less than 10 spines; male abdomen with margins sub-parallel; medial portion of sternites IV, V and VI with small spines near posterior margins; sternite VII with small oblique concavities on lateral areas, posterior margin with strong medial groove; length of spine of connexivum about 7/10 of the length of medial part of tergite VIII; proctiger with basolateral processes long, sharp apically, directed forward and visible dorsally, not reaching connexival spines.

Description. Apterous; total length (♂: 16 mm; ♀: 17, 6 mm); distance between meso-acetabulae (♂: 2,12; ♀: 2,33 mm). Head: length of segment I of antennae about 1.5 times length of segments II and III together; segment III about 0.5 as long as segment IV; segment IV measuring about 0.8 width of head and slightly curved; rostrum with segment III with setae covering about 1/3 dorsal end of anteroventral region; segment III about 1.7 times longer than segment IV; width of eyes, in dorsal view, between 1.29 to1.70 times interocular width. Thorax: mesonotum 2.18 to 2.26 times longer than pronotum and metanotum together; fore femora with anterodorsal region bearing less than 10 short spines, fore tarsi slightly shorter than hind tarsi; without anterior meta-acetabula tuft of setae. Male: abdomen, in dorsal view, with lateral margins slightly parallel, tergite II equal in width or slightly narrower than tergite VII; sternites IV, V and VI with small spines near posterior margin medially; tergite VIII with lateral margins on basal 1/3 slightly rounded, posterior region slightly parallel and posterior margin slightly truncated (fig. 0 1 and 02); pygophore in lateral view with apex rounded; proctiger, in dorsal view, with length subequal to length of tergite VIII, basolateral processes long, sharp apically, directed forward, visible dorsally, not reaching spines of connectives (Fig. 03); aedeagus elongate, about twice as long as wide, with sclerite basally bifid, branches about twice longer than area of confluence; apex slightly rounded. Female: apex of tergite VIII slightly rounded, spines of connectives between 0.26 and 0.28 mm. (Fig. 04); gonocoxae without spines posteriorly (fig. 05).

Coloration. Generally dark brown (Figs. 0 6 and 07). Head: in dorsal view, yellowish at margin of eyes, with brown longitudinal stripe extended to anterior region and front-clypeus and antennal tubercles blackish apically (Fig. 08), ventral view with longitudinal stripe dark brown medially, lateral areas of gula and gena yellowish, rostrum with segments I and II yellowish, segment III blackish, sometimes yellowish (Fig. 09). Thorax: pronotum with medial light brown groove; prosternum, acetabula, coxae, trochanters and femora yellowish; tibiae blackish, mesonotum and metanotum sometimes with blackish stripe limited medially by dark brown stripes, or completely brown; mesopleuron and metapleuron usually with brownish stripe dorsally, with two golden stripes separated by brownish stripe; mesosternum and metasternum brownish, covered with grayish pubescence; middle and hind femora yellowish, gradually darkening toward apex. Abdomen covered by slightly golden pubescence; tergites, pleurites and sternites (I – VII) brown; connectives yellow; spines of connectives dark brown. Male: tergite VIII brown or light brown; basal area of the sternite VIII and pygophore yellow, apical area and proctiger brownish. Female: tergite VIII, gonocoxae and sternite VIII brownish.

Measures. (Males): CT 16; ATI 1,9–2,01–2,08; ATII 0,72–0,78–0,85; ATIII 0,55–0,58–0,6; ATIV 1,1–1,13– 1,16; DTO 1,52–1,56–1,62; LGO 0,53–0,56–0,58; DIO 0,34–0,34–0,36; CRIII 0,56–0,57–0,59; CRIV 0,33–0,34– 0,35; CMTA 0,82–0,85–0,88; LGI 2–2,12–2,21; CMTP 1–1–1; LGII 1–1,23–1,37; LGIII 1,01–1,18–1,32; CMOTS 0,87–0,87–0,87; CMEC 0,6–0,64–0,67; LGPL 0,92–0,98–1,08; CMPL 0,96–1–1,08; CMPP 0,55–0,56–0,59; LGPPI 0,17–0,18–0,2; LGPPII 0,04–0,04–0,05. (Females): CT 17,5–17,68–17,87; ATI 2,27–2,33–2,4; ATII 0,7– 0,73–0,76; ATIII 0,52–0,52–0,52; ATIV 1,05–1,09–1,13; DTO 1,56–1,59–1,62; LGO 0,53–0,54–0,56; DIO 0,34– 0,37–0,41; CRIII O,55–0,55–0,55; CRIV 0,33–0,33–0,33; CMTA 0,86–0,88–0,9; LGI 1,57–1,98–2,4; CMTP 1,09–1,12–1,16; LGII 1,56–1,56–1,56; LGIII 1,18–1,21–1,25; CMOTS 0,65–0,74–0,84; CMEC 0,26–0,27–0,28.

Comments. In addition to the features mentioned by Drake (1952) the species of Group 1 sensu Drake 1952 ( C. bassleri , C. bilobatus , C. erythropus , C. linearis and C. meloi sp. nov.) differ from the species of the Group 2 sensu Drake 1952 ( C. hungerfordi , C. palmaris , C. podargus , C. regulus and C. stygius ) because (1) they have yellowish head at margin of eyes, with brown longitudinal stripe extended to anterior region and front-clypeus; (2) fore tarsi slightly shorter than hind tarsi; (3) without anterior meta-acetabula tuft of setae; (4) proctiger with length subequal to length of tergite VIII; and (5): basolateral processes of proctiger long and directed forward. While the species of Group 2 sensu Drake 1952 (1) have variable color of head from yellowish to blackish, without brown longitudinal stripe extended to former front-region and clypeus; (2) fore tarsi slightly larger than hind tarsi (except C. podargus ); (3) with anterior meta-acetabula tuft of setae (except C. podargus ); (4) proctiger with length twice to length of tergite VIII; and (5) basolateral processes of proctiger short and directed laterally.

Cylindrostethus meloi sp. nov. is similar to C. bassleri , C. bilobatus , C. erythropus and C. linearis but it is distinguished from C. erythropus , C. linearis and C. bassleri by the basolateral process of the proctiger, which has a sharp apex. It is distinguished from C. bilobatus by the length of the basolateral processes, which are longer.

Another diagnostic feature between these latter two species is the presence of small spines only on the central portion of the posterior margin of sternites V and VI in C. meloi sp. nov. Such spines are by contrast present along the entire posterior margin of sternites V and VI in C. bilobatus . Heckman (2011) illustrated one specimen identified as C. bassleri which has basolateral processes with sharp apices. After the analysis of the paratype of C. bassleri (deposited in the American Museum National of History) and the photograph of the holotype, we have concluded that Heckman’s specimen in fact represents C. meloi sp. nov.

In the identification key by Moreira et al. (2011a), the authors illustrated what was supposed to be a specimen of C. bassleri . We have studied their specimens and listed them in the present manuscript as the type material of C. meloi sp. nov.

According to Moreira et al. (2011a), specimens of C. meloi sp. nov. inhabit lotic water bodies and were captured in a small stream that houses a large population of C. erythropus . The stream was shallow and narrow, probably a first-order stream, with the bottom covered with sand. The dominant vegetation on the banks was primary and secondary vegetation, with the canopy shading the ground only partially. The margins consisted of primary and secondary vegetation, only partially covered by the canopy.

Figures

FIGURES 1 – 9. Cylindrosthetus meloi sp. nov.: (1): male genitalia, dorsal view; (2): male genitalia, ventral view; (3): male proctiger; (4) female genitalia, dorsal view; (5): female genitalia, ventral view (6): holotype male, dorsal view; (7): paratype female, dorsal view; (8): head, dorsal view; (9): head, lateral view.