Trigonopterus ellipticus (Pascoe)

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 : 7-12

Trigonopterus ellipticus (Pascoe)

Idotasia elliptica Pascoe, 1871: 262 . Type locality: Ceram.

( Figs. 14–32 )

Diagnosis. Body ( Fig. 15 ) subrhomboid, black, polished. Rostrum ( Fig. 17 ) with distinct median ridge posteriorly continuing to forehead. Disc of pronotum densely punctate. Elytral striae with small, sparse punctures; intervals flat, impunctate. Femora ( Fig. 14 ) with anteroventral ridge crenate, terminating with tooth behind middle of femur. Metafemur subapically with stridulatory patch. Aedeagus ( Figs. 21–22, 25–26 ).

Description. Lectotype, male ( Figs. 14–27 ). Length. Pronotum + elytra 2.8 mm.

Color black, except antenna and tarsi dark ferruginous, legs dark ferruginous to black. Integument of elytra and pronotum polished, punctate, nude; punctures of femora each containing silvery-grey recumbent scale, dorsal edge of meso- and metafemur and base of rostrum with silvery-grey recumbent scales not fully concealing the cuticle, partly abraded.

Habitus subrhomboid, with shallow constriction between prothorax and elytra; body in profile dorsally evenly convex. In thanatosis ( Fig. 18 ) legs sticking out from horizontal body plane at ca. 80°; dorsal edge of metafemur distant from elytral edge; tibiae largely left exposed; gaps between legs distinct, especially at base.

Rostrum ( Figs. 14, 17 ) ca. 2.4 X as long as wide at base, markedly curved ventrad; in profile dorsal contour basally convex, in straight line to apex; ventral contour subparallel, concave; dorsally with distinct median ridge and pair of similar submedian ridges, sulci between ridges containing each one row of mesally directed grey recumbent scales, largely abraded in lectotype; ridges flattening subapically, posteriorly median ridge continuing to forehead; epistome simple, without tooth, cuticle shining, sculpture shallow, with scattered setae.

Head. Eye subrotund, largely concealed by pronotum when in thanatosis position; dorsal margin forming indistinct ridge, bordered by furrow on adjoining forehead. Forehead between eyes almost as wide as rostrum (0.95 X), foveate, vertex behind eyes smooth, impunctate.

Antenna inserted somewhat behind middle of rostrum. Scape short, subequal to article 1 + 2 of funicle, fully concealed in rostral channel in thanatosis position.

Pronotum 1.24 X wider than long, widest at base, sides converging in straight line to apex, only laterally with traces of weak subapical constriction; anterior and posterior margin straight; disc densely punctate, narrow midline impunctate; along submedian line with 17 punctures; interspaces subequal to puncture´s diameter, glabrous; smoothly rounded towards sides, punctures becoming fewer but larger laterally; postocular lobe subangulate, continuous with slightly concave profile of marginal carina, antecoxal projection of marginal carina distinct, subacute, directed ventrad; side above procoxa simple, without fovea.

Elytra subovate, basally subtruncate, 1.33 X longer than wide, 1.29 X wider than base of pronotum, widest in basal quarter (0.26) of elytral length; profile dorsally smoothly convex, 0.53 X as deep as long; striae marked by row of small sparse punctures and partly by very thin hairline impressions; flat intervals impunctate, interspaces glabrous, polished; punctures of transverse row bordering basal margin somewhat denser and larger than elytral punctures behind; subbasally striae 8 and 9 with normal punctures, intervals simple, without any ridge; subapically stria 9 with dense and rather deeply impressed punctures; elytral apex simple, jointly evenly rounded, not extended ventrad.

Thoracic venter. Fig. 16 . Procoxa anteriorly punctate, posteroapically with tooth, mesal face subglabrous, without row of deep punctures. Ventral setose fringe of hypomeron forming indistinct receptacle brush; modified setae medially slightly longer than later ones. Mesothoracic receptacle broadly U-shaped with short side-walls; ventrally produced to level of mesocoxal apex; posteriorly subglabrous, coriaceous, dull, with median costa and pair of lateral costae, ventral rim coriaceous, nude. Mesocoxa punctate, with sparse setae, posteriorly with two small teeth. Metaventrite medially 1.3 X longer than exposed part of mesoventrite, disc broadly concave, medially subglabrous, sublaterally deeply punctate; lateral intercoxal ridge markedly protruding ventrad, in lateral aspect ventrally obliquely truncate, in ventral aspect intercoxal ridge somewhat oblique, its anterior end rotating slightly mesad; posteriorly intercoxal ridge weakly extending over metacoxa; anterior rim of metacoxal cavity without secondary denticle. Sides of metaventrite glabrous, ventrally bordered by costa; lateral surface of intercoxal ridge coriaceous, with few coarse punctures. Metacoxa subglabrous, possibly abraded.

Legs. Femora markedly compressed laterally; with distinct anteroventral ridge overlapping bent tibia, slightly in front of middle with bluntly angulate tooth; posteroventral ridge indistinct; anteroventral furrow distinct. Pro-, meso- and metafemur of similar size, sides subparallel. Profemur anteriorly polished, punctate; posteriorly weakly concave, dull, densely coarsely punctate-rugose; punctures of posterior surface containing inconspicuous scales; dorsally simple, without scaling. Mesofemur similar to profemur, but posterior surface rather convex, partly impunctate and dull, partly with deep punctures. Metafemur in repose reaching elytral apex; anterior surface polished, densely punctate, punctures containing each one recumbent scale; anteroventral ridge crenate; posterior surface largely smooth, dull; bordering posteroventral ridge with furrow containing row of squamiferous punctures, dorsally with additional row of punctures; subapical posterior surface with distinct stridulatory patch of transverse striation; basal limits of stridulatory patch ill-defined; dorsoposterior edge with indistinct row of 6 denticles, dorsal surface densely punctate, with white recumbent scales, partly abraded; suture with trochanter oblique with ventral edge. Tibiae with fine longitudinal ridges bordered by rows of dorsad pointing setae; dorsal edges of protibia simple, of meso- and metatibia with sparse row of denticles; apex with uncus and presumably with smaller premucro [partly worn off in lectotype]. Anterior setose comb of metatibia subapically following midline of metatibia from base of uncus; Tarsi with tarsomere 3 subtrapezoid, anteriorly markedly widened, shape of apical lobes symmetrical; tarsomere 3 ca. 1.6 X as wide as tarsomere 2, their length subequal; claw-segment inserted at center of tarsomere 3; length of tarsomere 5 subequal to tarsomere 3; tarsal claws minute.

Abdomen. Ventrite 1 anteriorly with sparse squamiferous punctures, obliquely behind metacoxa with dentiform swelling; suture between ventrites 1 and 2 laterally deeply impressed, at middle completely effaced where ventrites 1 and 2 form common glabrous concavity. Ventrite 2 laterally simple. Ventrites 3-4 narrow, of equal length, each with one transverse row of squamiferous punctures. Ventrite 5 laterally coarsely punctate and with suberect white scales, at middle with deep finely punctate concavity; apex simple, not crenulate.

Terminalia. Sternite VIII ( Figs. 23–24 ) subtrapezoid, sides converging to broadly incised apex, at base 2.0 X wider than long; membranous median suture separating two well-sclerotized lateral sclerites; apex sublaterally densely setose. Sternite IX ( Fig. 24 ) straight, apical arms somewhat widened, largely covered by sternite VIII. Tegmen ( Fig. 27 ) with complete, slender ring, apodeme relatively long, with indistinct unpaired parameroid lobe. Aedeagus ( Figs. 21–22, 25–26 ); body with sides subparallel, when viewed vertically sides converging to subangulate apex, sparsely setose, medially with rounded tip; in lateral aspect with constriction at middle, markedly widening towards apex; dorsal surface sublaterally with rows of sparse long setae; membrane of ostium transversely folded; with small subovate massive sclerite protruding from ostium, connected with pair of long endophallic sclerites contained in aedeagal body; apodemes ca. 2.0 X as long as aedeagal body; transfer apparatus ( Figs. 25-26 ) relatively simple, symmetrical, dagger-shaped; ductus ejaculatorius longer than aedeagus, internally strongly sclerotized, basally near insertion with transfer apparatus relatively thin, more apically with marked swelling (“bulbus ejaculatorius”) sclerotized and stainable with chlorazol black, apical portion broken off and missing.

Paralectotype, female. Figs. 19–20 , 28–32 . Same as lectotype except: length. Pronotum + elytra 2.58 mm. Rostrum with dorsal ridges limited to basal third, less prominent, not extending onto forehead; apical half polished, with pair of lateral furrows and submedian row of punctures bearing minute setae. Thoracic venter. Disc of metaventrite weakly concave. Abdomen. Ventrites 1–2 flat; ventrite 5 flat. Terminalia ( Figs. 28–32 ). Tergite VIII ( Fig. 32 ) 1.3 X longer than wide, spatulate, apical tip evenly rounded, simple, not crenulate. Sternite VIII ( Fig. 29 ) with apodeme curved to the right; apical plate subtrapezoid, medially with membranous area, apex sinuate, in apical half densely setose. Coxite ( Fig. 30 ) without conspicuous setae, 3 X as long as stylus. Stylus ( Fig. 30 ) with sides weakly converging, apex with few long stiff setae. Bursa copulatrix ( Fig. 28 ) membranous, without sclerites; ductus spermathecae sclerotized throughout, thick-walled, at middle dilated, thicker than spermatheca. Spermatheca ( Fig. 31 ) apically with relatively wide lumen; apical 1/2 solid chitinous, forming laminate process.

Material examined. Type specimens. Male, lectotype by present designation: INDONESIA, Maluku: Ceram Isl.; labels ( Fig. 20 ): 1) [blue, ovate] “male and female gender symbol, Ceram [hand-written]” 2) [rectangular, white] “ Idotasia elliptica Pasc. , Type [hand-written]” 3) [rectangular, white with black margin] “ Idotasia elliptica Pasc. [hand-written]” 4) [rectangular, white] “Pascoe Coll. B.M.1893-60 [printed]” 5) [round, white with blue margin] “ SYNTYPE [printed]” 6) [rectangular, red] “ LECTOTYPE, Idotasia elliptica Pascoe , det A.Riedel 2007 [printed]”; condition: fair, slightly abraded, right antennal club and right mesotarsus broken and missing; specimen originally card-mounted, remounted on point; genitalia in glycerol in microtube ( BMNH). Paralectotypes: 1 female, 1) [white, rectangular] ““Ceram”, same label as Lectotype [printed]” 2) [white, rectangular] “originally mounted on one card with lectotype [printed]”; 3) [rectangular, red] “ Paralectotype, Idotasia elliptica Pascoe , det. A. Riedel 2007 [printed]” ( BMNH); 1 male, Batchian; labels: 1) [blue, ovate] “Batchian [hand-written]” 2) [rectangular, white] “male and female gender symbol, elliptica , 1 line illegible [hand-written]” 3) [rectangular, white] “Pascoe Coll. B.M.1893-60 [printed]” 4) [rectangular, red] “ LECTOTYPE, Idotasia elliptica Pascoe , det A.Riedel 2010 [printed]”; specimen originally card-mounted, remounted on point; genitalia in glycerol in microtube ( BMNH); 1 female, Batchian; labels: 1) [white, rectangular] ““Batchian”, same label as Lectotype [printed]” 2) [white, rectangular] “originally mounted on one card with lectotype [printed]”; 3) [rectangular, red] “ Paralectotype, Idotasia elliptica Pascoe , det. A. Riedel 2010 [printed]” ( BMNH).

Other specimens. 1 female, Maluku, Ceram Isl., leg. Wallace, Fry collection ( BMNH).

Distribution. INDONESIA, Maluku (Ceram Isl., Batchian Isl.?).

Notes. Pascoe (1871) did not designate a holotype in the original description nor specify the number of specimens examined. Four syntypes could be located, two each from Ceram and Batchian. Other specimens may exist in addition to them. The male from Ceram is here designated lectotype to ensure stability of nomenclature in case additional syntypes are discovered that belong to different species. Originally, two specimens were each mounted on one card and provided with one set of labels. The specimens were mounted on cards on separate pins by the present author. Locality data were transcribed to a second set of labels for the female specimens.

Two undescribed species from Waigeo Island, respectively from Salawatti and Batanta Islands are similar to T. ellipticus (Pascoe) , but can be distinguished by slightly deeper and denser punctation of the pronotum, slightly more distinct femoral teeth and most clearly by a different structure of aedeagus and transfer apparatus. It is likely that T. ellipticus (Pascoe) is endemic to Maluku. Considering the degree of endemism usually exhibited by Trigonopterus species, it is somewhat surprising that specimens from Ceram and Bacan look almost identical. Additional fieldwork is needed to clarify if T. ellipticus (Pascoe) occurs on both islands, or if it is an endemic to only one of them, with the record of the other being incorrect.

Figures

FIGURES 14 – 20. Trigonopterus ellipticus, lectotype: (14) lateral aspect; (15) dorsal aspect; (16) ventral aspect; (17) frontal aspect; (18) thanatosis position, lateral aspect; (19) as originally mounted besides paralectotype on the right; (20) labels.

FIGURES 21 – 27. Male terminalia of Trigonopterus ellipticus, lectotype: (21, 25) aedeagus, lateral aspect; (22, 26) aedeagus, dorsal aspect; (23 – 24) sternite VIII – IX; (27) tegmen.

FIGURES 28 – 32. Female terminalia of Trigonopterus ellipticus, paralectotype: (28) overview; (29) sternite VIII; (30) coxite; (31) spermatheca; (32) tergite VIII.