Mixotrephes (Pictotrephes), Papáček & Zettel, 2011

Papáček, Miroslav & Zettel, Herbert, 2011, A new subgenus and species of Mixotrephes (Hemiptera: Heteroptera: Helotrephidae) from Laos and notes on Mixotrephes punctatus, Acta Entomologica Musei Nationalis Pragae 51 (2), pp. 397-406 : 398-402

Pictotrephes subgen. nov.

Type species. Mixotrephes (Pictotrephes) pictus sp. nov., by present designation.

Diagnosis. Body shape, lateral cephalonotal carina, size of cephalonotum, length of rostrum, general shape of right paramere, and structures of first valvulae of ovipositor as typical for the genus Mixotrephes . Ground colour chiefly blackish; with some yellow marks ( Figs. 1–6 ). Cephalonotum (posteriorly) and mesoscutellum coarsely sculptured with minute tubercles (in addition to punctures). Mesoscutellum wide, with conspicuously convex sides ( Fig. 9 ). Midventral abdominal carinae on sterna 2–6. Process of pygophore low and round. Aedeagus simple, unmodified, evenly tapered towards round apex. Subgenital plate of female unmodified, broad, posteriorly widely rounded.

Etymology. Compound from ‘ pictus ’, referring to the type species, and ‘ trephes ’, meaning inhabitant, the most frequent ending of generic epithets in Helotrephidae . Gender: masculine.

Comparative notes and discussion. The new subgenus is erected for the single species M. (P.) pictus sp. nov. Mixotrephes pictus does not fit well in any generic taxon of Limnotrephini . Its provisional placement in Mixotrephes is based on overall similarities, such as the body shape, coloration, median length of cephalonotum not exceeding half the length of the body, lateral cephalonotal carina arrow-wise penetrating onto the ocular area, lateral pronotal plate without insinuation at the meeting point with genal plate, triangular propleural plate with acuminate apex, short labium reaching between fore coxae, type of pygophore with spur-like process in males, and shape of the 1 st valvulae in females. But it cannot be placed in any of the subgenera, Mixotrephes s. str. and Thermotrephes , because of differences in some characters diagnostic for them (see Tab. 1). A study of Limnotrephini phylogeny is still not available. However, by comparison of several characters, Pictotrephes seems to take a very basal position in Mixotrephes , if not in the entire tribe Limnotrephini (see also below). The supposedly plesiomorphic characters of Pictotrephes , that support its basal position, at the same time distinguish it from one or both congeneric subgenera: weakly modified midsternal thoracic carina; simple aedeagus (phallosoma) without apical modification; simple, almost unmodified subgenital plate of the female; and first valvulae of ovipositor with dense cluster of apical bristles (compare Fig.16 and Fig. 8 in PAPÁČEK & ZETTEL (2008: 89)).

Two plesiomorphic characters of Pictotrephes are worth to be discussed: (i) Medial carinae of abdominal sterna, formed by separated lamellae with posteroventral tips, are located on sterna 2–6 in both sexes (but only minute in male). Extension to sternum 6 is a synplesiomorphy with Pleidae (Pleoidea) (see also discussion on this character by PAPÁČEK & ZETTEL (2006: 29, 30)). However, the simple reduction of carinae on sterna 5 and 6 (in varying extent) is probably not a synapomorphy of all other Limnotrephini genera (see similar convergencies in Helotrephini). (ii) The process on the male’s pygophore (= ‘spur-like process’ in other Limnotrephini ) is weakly developed as compared to other genera (see also discussion in PAPÁČEK et al. (1989: 120, 121)). Also here, we can see only gradual differences.

A few characteristics of Pictotrephes subgen. nov. are unique within Limnotrephini and appear strongly derived: The relatively wide and convex mesoscutellum (compare Figs. 9 and 10 ) and the tuberculate sculpture of cephalonotum and mesoscutellum. Both are considered to be autapomorphies.

Accumulation of plesiomorphic characters of Pictotrephes subgen. nov. showing its possible basal position in the whole genus or in the tribe Limnotrephini respectively, and its provisional placing in Mixotrephes based on overall similarities (cluster – or combination of characters respectively), can suggest that present genus Mixotrephes is paraphyletic.

Figures

Figs. 1–6. Mixotrephes (Pictotrephes) pictus sp. nov. 1–3 – holotype (male), 4–6 – paratype (female). 1, 4 – frontal; 2, 5 – dorsal; 3, 6 – lateral view. In Fig. 6, base of hemielytron not in normal position, covering posterolateral corner of cephalonotum. © NHMW Hemiptera Image Collection.

Figs.9–16. Structural characters of Mixotrephes (Pictotrephes) pictus sp. nov. (9, 11–16) and Mixotrephes hoberlandti Papáček, Štys & Tonner, 1989 (10). 9, 10 – outlines of cephalonotum and mesoscutellum from dorsal view (except M. (P.) pictus sp. nov., all other known Mixotrephes species have the same basic shape of mesoscutellum as M. hoberlandti); 11 – phallosoma; 12 – left paramere; 13 – right paramere; 14 – male abdominal sternum 8; 15 – female subgenital plate; 16 – first right valvula from ventral view. Scale bars: A = 1.0 mm (Figs. 9, 10), B = 0.2 mm (Figs. 14, 15), B = 0.1 mm (Figs. 11–13, 16).

Figs. 7–8. Type locality of Mixotrephes (Pictotrephes) pictus sp. nov., Laos, Champasak Prov., Bolaven Plateau, Tad Yueang waterfall. 7 – general view on the Tad Yueang waterfall; 8 – micro- habitat of the species – shallow puddles on rocky bank in the ‘spray zone’ of a waterfall. Photographs by Jiří Hájek.