Trigonopterus oblitus, Riedel, Alexander, 2011

Riedel, Alexander, 2011, The weevil genus Trigonopterus Fauvel (Coleoptera, Curculionidae) and its synonyms — a taxonomic study on the species tied to its genus-group names, Zootaxa 2977, pp. 1-49 : 34-36

Trigonopterus oblitus sp.n.

( Figs. 108–119 )

Diagnosis. Body ( Fig. 108 ) small, 1.7 mm; densely punctate, microreticulate, dull. Elytral striae deeply impressed, punctures bearing short suberect setae; interval 1 and 7 swollen, apically connected. Metafemur without stridulatory patch. Tarsomere 5 long, claws relatively large. Sternite VIII ( Fig. 116 ) vestigial, sternite IX forming large exposed “V”. Aedeagus ( Figs. 114–115, 117–118 ); ostium with 3 brace-like sclerites.

Description. Holotype, male ( Figs. 108–119 ). Length. Pronotum + elytra 1.7 mm.

Color black with minor deep ferruginous areas, antenna and tarsi lighter ferruginous. Integument of elytra and pronotum markedly sculptured, sparsely setose.

Habitus subrhomboid, with marked constriction between prothorax and elytra; profile dorsally with constriction between pronotum and elytron. In thanatosis ( Fig. 113 ) legs sticking out from horizontal body plane at ca. 60°; dorsal edge of metafemur distant from elytral edge; femora loosely fitting against each other; tibiae largely left exposed; gaps between legs distinct, especially at base.

Rostrum ( Figs. 109, 111 ) ca. 2.5 X as long as wide at base, widest basally and subapically, sides concave; in profile evenly convex; dorsal surface dull, scabrous-rugose, with distinct median ridge and pair of very indistinct submedian ridges; with very inconspicuous rows of mesally directed setae; epistome short, slightly depressed, without tooth, smooth, shining, apically with few long setae.

Head. Fig. 109 . Eyes subovate, not fully concealed by pronotum when in thanatosis position. Forehead between eyes slightly narrower than rostral base (0.9 X), irregularly punctate-rugose.

Antenna inserted at middle of rostrum. Scape subequal to article 1 + 2 of funicle, partly exposed in thanatosis position.

Pronotum 1.40 X wider than long, widest in posterior third; sides markedly rounded to shallow subapical constriction; anterior and posterior margins subtruncate; disc densely deeply punctate, punctures becoming ovate towards middle; each puncture containing one subrecumbent seta; along submedian line with 8 punctures; interspaces between punctures narrower than puncture´s diameter, glabrous, shiny; subbasally microrugose, subapically punctate-rugose; disc smoothly rounded towards alveolate sides; weak postocular lobe separated by shallow constriction from convex profile of marginal carina, antecoxal projection of marginal carina angulate, directed ventrad; side above procoxa simple, punctate, without fovea.

Elytra pyriform, basally truncate, 1.32 X longer than wide, 1.15 X wider than base of pronotum, widest in basal 0.29 of elytral length; subbasally with shallow constriction; in profile dorsally smoothly convex, 0.58 X as deep as long; striae deeply impressed, with short subrecumbent setae, punctures indistinct; intervals costate, subglabrous, irregularly transversely rugose; at base and near humerus simple; interval 1 and 7 swollen, apically connected; elytral apex simple, suture weakly incised, not extended ventrad.

Thoracic venter. Fig. 110 . Procoxa anteriorly and posteriorly coriaceous, subapically with tooth, sparsely setose; mesal face subglabrous, without punctures. Ventral setose fringe of pronotal hypomeron without receptacle brush; medially with gap. Mesothoracic receptacle broadly V-shaped; ventrally produced slightly beyond level of coxal apices; posterior surface microreticulate, dull, with pair shallow impressions, sparsely setose. Mesocoxa simple, without tooth. Metaventrite medially shorter (0.8 X) than exposed part of mesoventrite, disc broadly concave, microreticulate, punctate, sparsely setose; lateral intercoxal ridge weakly protruding ventrad, dentiform, in lateral aspect transversely truncate; anterior rim of metacoxal cavity without secondary denticle. Sides of metaventrite irregularly sculptured, center with few large punctures, dorsally with costa bordering epipleuron. Metacoxa in mesal angle swollen, dentiform, with one long seta.

Legs. Femora moderately compressed laterally. Pro-, meso- and metafemur of similar size; weakly clavate, narrow; metafemur apically somewhat curved ventrad; femora markedly microreticulate, dull, punctate, punctures containing each one recumbent seta; with indistinct anteroventral ridge; posteroventral ridge indistinct, almost absent; without ventral teeth, but anteroventral ridge of meso- and metafemur with very indistinct knob; anteroventral furrow indistinct. Metafemur in repose not reaching elytral apex; its dorsoposterior edge simple, without scales or denticles; subapically posterior surface without stridulatory patch; suture with trochanter oblique to ventral edge. Tibiae markedly microreticulate, with very indistinct longitudinal ridges, with sparse rows of recumbent setae; dorsal edges simple, without denticles; apex with long uncus, without premucro. Anterior setose comb of metatibia subapically following midline of metatibia from base of uncus. Tarsi with tarsomere 3 subovate, shape of apical lobes asymmetrical, anterior lobe larger; tarsomere 3 ca. 2 X as wide as tarsomere 2, 1.8 X longer than tarsomere 2; claw-segment inserted at center of tarsomere 3; tarsomere 5 relatively long, 1.4 X as long as tarsomere 3; tarsal claws small, distinct.

Abdomen. Ventrites markedly microreticulate, dull, with sparse inconspicuous setae. Ventrite 1 behind metacoxa with swelling; with curved row of deep, setiferous punctures. Ventrites 1 and 2 medially forming common concavity; suture between ventrites 1-2 laterally distinct, medially effaced. Ventrite 2 along posterior margin raised, forming edge. Ventrites 3-4 narrow, of equal length, raised, forming edges. Ventrite 5 impunctate, at middle with concavity; apex double-folded with a smooth thin dorsal plate originating on dorsal surface of ventrite 5; apex of true ventrite 5 shortened, with sparse long setae; apex of dorsal process of ventrite 5 glabrous, smooth, closing with elytral margin.

Terminalia. Sternite VIII ( Fig. 116 ) vestigial, ca. 6 X as wide as long, consisting of sparsely setose pair of sclerites medially connected by membrane. Sternite IX ( Fig. 116 ) weakly curved to the right, in apical 1/3 arms forming “V”, largely exposed. Tegmen ( Fig. 119 ) Y-shaped, apodeme short, dorsal portion of ring absent. Aedeagus ( Figs. 114–115, 117–118 ); with sides of body subparallel, apex subangulate, medially extended into short rounded tip; apex slightly asymmetrical, right side more retracted compared to left side; ventral margin of basal orifice extended apicad; subglabrous, dorsal surface and apex subglabrous, without setae; ostium with distinct bracelike sclerites, one median sclerite and pair of lateral ones; apodemes ca. 0.9 X as long as aedeagal body; transfer apparatus entirely contained within aedeagal body, symmetrical, but somewhat tilted to left side, base of ductus ejaculatorius inserting into half open capsule, extended into short ventrad pointing tooth; ductus ejaculatorius ca. 2 X as long as aedeagus, internally strongly sclerotized, basally where leaving basal orifice relatively thin, more apically with marked swelling (“bulbus ejaculatorius”).

Material examined. Holotype, male: PAPUA NEW GUINEA, Madang Prov.: Astrolabe Bay, Mt. Hansemann [Google Earth: S 5° 9.993´, E 145° 44,991´], leg. Biró 1901 ( HNHM). Paratypes: PAPUA NEW GUINEA, Madang Prov.: 1 male, Montes Hansemann, leg. Biró 1896 ( HNHM).

Distribution. PAPUA NEW GUINEA, Madang (Mt. Hansemann).

Etymology. The epithet is based on the Latin oblitus (forgotten) and refers to the fact that it was probably part of the type series of Microgymnapterus minutus Voss from which it is clearly distinct.

Notes. This species is closely related to T. vossi . Both share the peculiar morphology of the male ventrite 5 with a double-folded apex, the morphology of male sternites VIII-IX, a Y-shaped tegmen, and an aedeagus with an extended ventral margin of the basal orifice.

It was attempted to extract DNA from the holotype, but no successful PCR amplification was achieved.

Figures

FIGURES 108 – 113. Trigonopterus oblitus sp. n., holotype: (108) dorsal aspect; (109) frontal aspect; (110) ventral aspect; (111) lateral aspect; (112) labels; (113) thanatosis position, lateral aspect.

FIGURES 114 – 119. Male terminalia of Trigonopterus oblitus sp. n., holotype: (114, 117) aedeagus, lateral aspect; (115, 118) aedeagus, dorsal aspect; (119) tegmen; (116) sternite VIII – IX.