Metallactus viator, Sassi, 2019

Sassi, Davide, 2019, Revision of the Metallactus hamifer species-group (Coleoptera: Chrysomelidae: Cryptocephalinae), Zootaxa 4657 (2), pp. 201-245 : 239-241

Metallactus viator sp. nov.

( Figs 17 ; 34 )

Type. HOLOTYPE: ♀, glued, genitalia and detached abdomen glued on a separate card // “ Paraguay leg. Fiebrig ” [white label, printed] // “ Metallactus viator sp. nov . HOLOTYPUS D. Sassi des.” [red label, printed] // ( MNHUB) .

Type locality. “ Paraguay ” .

Etymology. Latin noun meaning “traveller”. The word viator is intended here as a noun in the nominative singular, standing in apposition to the generic name (articles 11.9.1.2 and 31.2.1 of I.C.Z.N., 4th edition).

Distribution. Paraguay.

Diagnosis. A Metallactus of medium size. Dorsal color pattern approaches this species to the subgroup characterized by dark longitudinal stripes on pronotum and elytra ( M. praetorius , M. chamorroi , M. bivitticollis , M. agonista , M. pollictor , and striped form of M. hamifer ). Due to its somewhat ovate outline, it is the only species of the group having the maximum body width not at humeral callus but at the middle of elytron. Antennae are unusually short, with squat antennomera not reaching the humeral calli when directed backwards. This trait makes the only specimen in study inconsistent with any other species of the group and forced the creation of a new species even though on the basis of a single female. Moreover, other traits like the overall outline and the shape of the head strongly support this choice.

Description of female (male unknown). Habitus in Fig. 17 a–b (HT). BL = 6.1 mm, BW = 3.8 mm, PL = 2.0 mm, PW = 3.3 mm. Interocular distance 18.0% of BL.

Head yellow with two subtriangular black spots on vertex. Antennal insertions ochraceous. Labrum yellow. Whole head surface flat and broad, sublucid, almost devoid of setosity. Puctation rather feeble and sparse, only in middle of frons punctures are coarser and closer but still shallow.

Mid-cranial suture totally obliterated. Antennae blackish with antennomera 1-5 slightly light.

Pronotum ochraceous with two comma-like black stripes at middle of disc. Pronotal shape elliptical, little transverse. Lateral margins thin, almost not visible from above, regularly curved with maximum width just behind half length. Posterolateral impressions obliterated so that posterior margin not thickened behind them. Surface slightly flattened, shiny with scattered, feeble punctation almost obliterated in center of disc.

Scutellum yellow, darkened in middle section, shiny, distinctly raised, finely setose and minutely punctured. Quite short, transverse, with apex truncated in a straight line.

Elytron surface yellow with two longitudinal, narrow, black stripes extending from anterior margin to apical clivus. Inner stripe in continuity with the pronotal one, slightly tapered posteriorly. Outer stripe running over humerous, scarcely tapered towards apex. Suture narrowly black. Elytral sides relatively arcued and slightly convergent towards apex, so that outline somewhat different from usual cylinder-shaped one. Lateral margin rather large compared to other species, so that visible from above from humera to elitral apex. Postscutellar area completely flat. Humeral callus scarcely prominent, impunctate. Surface moderately shiny with fine, weakly impressed punctures, very irregularly distributed in inner part of disc, laterally arranged in irregular rows. Intervals flat.

Pygidium yellow, smooth, covered with sparse shallow punctures and whitish setae.

Inferior parts of thorax totally ochraceous. Hypomera, mesoepimera and mesoepisterna almost bare with rather coarse, shallow punctures. Metaepisterna and metasternum with quite coarse punctation and sparse setae. Prosternal process coarsely punctured with long setae, deeply depressed along midline, with slightly raised short triangular apex. Abdominal ventrites completely yellow to brownish, shallowly and sparsely punctured, with sparse setae. Legs ochraceous with tarsi, meso- and metatibial apex infuscate.

Fifth abdominal ventrite in female with quite long and deep pit. Bottom of pit bald, smooth, shiny, impunctate. Vasculum of spermatheca ( Fig. 17c ) relatively robust, scarcely pigmented with straight proximal branch fairly swollen at base, long mildly curved distal branch and apex pointed, downwards directed. Ampulla not pigmented, slightly shifted on dorsal side of vasculum. Duct insertion and sperm gland insertion perceptibly distinct. Duct uniform in size, slender, coiled with coils rather thick and quite regularly arranged. Distal not coiled portion of duct long, almost straight. Insertion on bursa copulatrix rather short, barely swollen, lightly pigmented.

Figures

FIGURES 16–17. M. tarsalis (16), M. viator (17). 16a–b: habitus; 16c–e: median lobe of aedeagus in ventral (c), dorsal (d) and lateral (e) view [0.6 mm]; 16f: sclerites of endophallus [0.4 mm]; 16g: antenna [2.2 mm]. 17a–b: habitus; 17c: spermatheca [0.6 mm]; 17d: antenna [1.8 mm]. 16a–b: paralectotype; 17a–b: holotype. hd: hairy dent; scI–IV: sclerites I–IV of endophallus; ds: dorsal spicule. Square brackets: length of scale segment.

FIGURES 27–34. Distribution maps for Metallactus hamifer species-group. M. luniger (27); M. madefactus (28); M. octoguttatus (29); M. pollinctor (30); M. praetorius (31); M. sekerkai (32); M. tarsalis (33); M. viator (34). Grey squares: localities reported in a generic way.