Metallactus longicornis Sassi 2018, sp. nov.
Creators: name: Sassi, Davide
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Chrysomelidae
Metallactus
Metallactus longicornis

description: Metallactus longicornis sp. nov.
(Figs 15; 31)
Etymology. The name refers to the unusual length of male antennae.
Type material. HOLOTYPE: ♂, glued, abdomen glued on the same label bearing the specimen, aedeagus, glued on a separate label, // “Bras. Sao Paulo Batatais J. Guerin XI-945” [white label, handwritten] // “ F. Monrós collection 1959” [white label, printed] // “ Metallactus longicornis sp. nov. HOLOTYPUS D. Sassi des.” [red label, printed] // (USNMNH). PARATYPES: 2♂ 8♀♀, same data of the holotype (USNMNH, DSPC); 1♂, // “Cuyaba Mtt. Grosso” [white label, printed] // “ex coll. J. Weise ” [white label, printed] // (MNHUB); 1♀, // “Brasilien Cuyaba O Staundiger ” [pale green label, printed] // (NHMB); 1♀, // “Bras. St. Paulo Brotas Rio Claro Baethge ” [green label, printed] // (NHMB); 1♀, // “ Mineiro Goyaz Brésil ” [white label, printed] // “ Metallactus dodecastictus Suffr. ” [white label, printed] // “ex coll. J. Achard National Museum Prague, Czech Republic ” [white label, printed] // (NHMP); 1♀, // “ Jatahy Etat de Goyaz Brésil” [white label, printed] // “ex coll. J. Achard National Museum Prague, Czech Republic ” [white label, printed] // (NHMP); 1♀, // “ Jatahy Prov. Goyas. Brésil Sept. a Nov. 97 ” [pale green label, printed] // “gift of F. C. Bowditch ” [white label, printed] // (USNMNH); 1♀, // “ Jatahy Prov. Goyas. Brésil Sept. a Nov.97 ” [pale green label, printed] // “Jacoby 2 nd coll.” [white label, printed] // “ F. Monrós collection 1959” [white label, printed] // “ Metallactus dodecastictus Suffr. F. Monrós det. 1954” [white label, partly handwritten] // (USNMNH); 1♀, “Matto Grosso Cuijaba” // (MHNH). All paratypes provided with additional label: // “ Metallactus longicornis sp. nov. PARATYPUS D. Sassi des.” [red label, printed] //.
Type locality. Batatais (São Paulo, Brazil).
Distribution. Brazil.
Diagnosis. A Metallactus of large size. On the basis of the peculiar features stressed in the description, M. longicornis does not fit in well with the diagnosis of the M. kollari species-group as regard its aedeagal shape, which is unique in having a strongly sculptured ventral surface. Anyway, according to the external habitus, this species must belong to this group and in particular it can be placed into the subgroup with subconical pronotal outline. This subgroup comprises also M. patagonicus, M. pollens, M. dodecastictus, M. rileyi and M. londonpridei and M. bezoar. Among these species, only M. londonpridei and M. longicornis have legs completely black. The black pronotal pattern is somehow distinctive, consisting of two well separate oblique spots. The body outline is less cylindrical than in the allied taxa, at least in males, being mildly tapered backwards. Also M. rileyi and M. londonpridei have well separate oblique spots on pronotum, but in both species there is also a small rounded additional spot in front of the scutellum. Besides, in M. rileyi antennomeres are normally shaped and shorter (Fig. 13n). M. londonpridei is the most similar as regards size and overall outline, being slightly tapered backwards as well. As the males are easily distinguished by the shape of aedeagus, females of these two species are quite difficult to diagnose. At present, only the structure of spermathecal duct is somewhat different, being much shorter in M. longicornis, with thicker coils and a constant cross section along the length. In M. londonpridei coils are looser and the distal trait has a slightly larger cross section. However, the absence of a fair black rounded little spot on pronotal disc in M. longicornis seems to supply some help in the identification of female specimens even without the examination of genitalia. In comparison with many other species, the entirely black ventral coloration, including abdominal ventrites and pygidium, and the strong setosity of inferior parts, fully covered by dense silvery setae, are quite significant as well. However, latter traits are also similar in M. kollari and M. londonpridei.
Description of male. Habitus in Fig. 15 a–b (HT) and 15a1 (PT). BL = 6.0 mm, BW = 3.5–3.6 mm, PL = 1.9– 2.0 mm, PW = 3.0– 3.1 mm. Interocular distance 9.2–10.8% of BL.
Head yellow with vertex, antennae insertion and inferior part of ocular canthus black. Labrum partly brownish. Surface matt with quite deeply impressed punctures, more concentrates on clypeus and ocular rim, slightly smaller on vertex. Frons with a quite long, well definite, narrow longitudinal groove. Antennae (Fig. 15n) black, only tips of first four antennomeres somewhat lighter. Antennomeres remarkably lengthened, so that antennae slightly exceed the total body length.
Pronotum yellow with two oblique elliptical spots on disc, not reaching margins, sometimes reduced to small rounded marks. Pronotal surface tronco-conical, moderately lengthened. Lateral margins slightly widened, almost regularly converging forwards and thus barely visible from above. Posterolateral impressions poorly marked, in correspondence of which posterior margin scarcely thickened. Surface moderately shining with quite dense and fairly impressed punctation on sides, almost obliterated on disc.
Scutellum totally black, with very minute and sparse puncturation, distinctly raised with truncated apex. Surface bearing quite apparent whitish setae.
Elytra yellow with three pairs of black spots. First pair of spots near anterior margin, obliquely transverse, fairly widened on humeral calli. Second one, transverse as well, just behind the middle. Third one, smaller and rounded, on elytral apex. Spots never reaching margins nor suture but sometimes reduced or partly obliterated. Suture narrowly black at least on apical half. Surface very weakly flattened on disc with sides slightly converging toward apex, at least in males, so that outline somewhat less cylindrical than in most of other species. Postscutellar area faintly raised with humeral calli prominent, impunctate. Surface moderately shiny with punctation small, quite dense, scattered, sometimes forming irregular rows with flat intervals.
Pygidium black, covered by quite deep and close, rounded punctures, setosity dense on basal half, more scattered towards apex.
Inferior parts completely black, only sides of hypomera partly yellow. Surface covered by dense silvery setae. Prosternal process normally shaped, longitudinally grooved with rounded and slightly raised apex and surface covered with coarse punctures and very long and dense setae. Legs, totally black.
Fifth abdominal ventrite with a median depression strongly impressed, smooth, bald, impunctate and a pair of small, flattened tubercles close to posterior margin which is deeply notched. Median lobe of aedeagus (Fig. 15 c–e) spatula-shaped with apical half widened and apex blunt to shortly pointed, slightly bent ventrally. Ventral surface deeply excavated into two large pits, separated by a longitudinal sharp carina. Pits are apically delimited by rather swollen hairy dents whose surface is covered by close, well developed whitish setae.
Endophallus (Fig. 15 f–g) with sclerite I strongly developed, wedge-shaped, fairly sclerotized with denticle obliterated. Dorsal spicule barely detectable, tiny, reduced to simple brownish patches on membraneous part of endophallus. Sclerite II scarcely to fairly developed, barely sinuate. Arch of sclerite III stout, short, evenly thickened with apex barely differentiated. Branches of sclerite IV just as long as sclerite III in the folded up structure, strongly enlarged at base, bluntly tapered and bent dorsally at apical half, with rounded apex and surface fairly rugose.
Female. BL = 6.2–7.2 mm, BW = 3.7–4.1 mm, PL = 1.9–2.2 mm, PW = 3.0– 3.6 mm. Interocular distance 12.2–13.9% of BL. Antennae not particularly lengthened, remarkably shorter than in males and not exceeding total body length.
Fifth abdominal ventrite in females with deep, oblong pit, fairly wedged below fourth and part of third visible sternite, with bottom dull, impunctate but covered by tiny wrinkles. Spermatheca (Fig. 15h) with upper branch gradually tapered in a straight, pointed apex. Lower branch almost straight to slightly sinuate at base. Ampulla fairly pigmented, rather lengthened, shifted on dorsal side of vasculum. Duct short, uniform in thickness, slender, coiled but coils somewhat loose, in particular in the last section. Insertion on bursa copulatrix feebly swollen. Rectal apparatus (Fig. 15 k–m) with dorsal sclerites laterally not projected beyond rectus, slender, vaguely tapered towards median line, with apodemes quite small, hyaline, bent upwards and leaning against rectum. Dorsal chitinous area caudal to dorsal sclerites fairly developed, deep, crossed by a well marked median longitudinal fold. Ventral sclerite large, ribbon-like, clearly tapered on sides, weakly pigmented in middle, with rounded apodemes, slightly projecting laterally.
Remarks. Metallactus longicornis is described in this paper and tentatively assigned to the present group of species even though the morphology of the male sexual characters fairly differs from what has been pointed out in the diagnosis of the species-group. In particular, the strongly differentiated aedeagal morphology and the deep impression on anal sternite look rather unusual. However, the decision was made on the basis of the overall shape, the size and the dorsal color pattern. Then again, the similarity with some of the other species in these external traits is so strong that it is extremely difficult to distinguish, if possible, females of M. longicornis from the ones of M. londonpridei. Making a different decision, the species would turn out to be isolated and very different from any other Metallactus species examined till now. For this reason, at least provisionally, the species has been integrated in the group which it seems to be more closely related to.
description: Published as part of Sassi, Davide, 2018, Revision of the Metallactus kollari species-group with a new diagnosis of the genus (Coleoptera: Chrysomelidae: Cryptocephalinae), pp. 57-110 in Zootaxa 4413 (1) on pages 95-96, DOI: 10.11646/zootaxa.4413.1.2, http://zenodo.org/record/3066636