Metallactus minax Suffrian 1866
Creators: name: Sassi, Davide
Publisher: name: Zenodo
Year: 2025
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Chrysomelidae
Metallactus
Metallactus minax

description: Species belonging to the Metallactus minax Suffrian, 1866 species-group:
Metallactus minax Suffrian, 1866
= Metallactus mosei Schöller, 2003 syn. nov.
Metallactus abstersus (Suffrian, 1866) comb. nov.
= Metallactus incultus Suffrian, 1866 syn. nov.
Metallactus tommasoi sp. nov.
General characters of the species group
In terms of overall external appearance, size, and dorsal coloration pattern, the species belonging to this group are comparable to those recently assigned to the Metallactus kollari (Perty, 1832) and Metallactus generosus Suffrian, 1866 species complexes (Sassi 2018, 2020a).
Distinctive features of the species group proposed here are primarily based on the shape of the median lobe of the aedeagus, which has a rounded spoon-like apex and a characteristic more or less pointed tubercle below the apex on the ventral surface. In two of the three species, this tubercle is particularly developed, forming a conspicuous sharp, conical process. Additionally, there is an unusually deep, heart-shaped depression on the fifth abdominal ventrite of the male. On the contrary, in the above-mentioned species complexes, the ventral aedeagal surface is basically smooth and devoid of particular structures, and the depression on the male fifth anal sternite is definitely shallower, with its rear margin only weakly notched or almost straight.
The overall dorsal coloration shows significant individual variability, which can create considerable difficulties in correctly identifying the species when examination of the median lobe of the aedeagus is not possible. However, a trait that seems to characterize this group of species quite well, compared to those mentioned above, is the coloration of the legs and ventral parts, which are generally totally or almost totally black, contrary to what is observed, for example, in the Metallactus kollari group, where specimens with predominantly light coloration on the ventral side and legs prevail. Additionally, the almost entirely black coloration of the forehead (rarely there is a small, blurred light marking between the antennal insertions), in both males and females, distinguishes the species M. minax and M. abstersus, while in the third species (M. tommasoi) the clypeofrontal surface is predominantly yellow.
The pronotal colouration can be totally black to black with margins and a longitudinal median stripe yellow. The elytral coloration is variable but falls into patterns that are quite common within the entire genus, namely a bicolored motif, with light parts in a yellowish or brick-red color, and dark parts represented by black spots variable in number, shape, and size, but with a predominant pattern consisting of a common large elliptical spot located in the center of the two elytra. This spot can appear significantly reduced, turning into a more or less oblique, separated pattern on each elytron, or it can be represented by a broad sutural band accompanied by other spots arranged longitudinally along the elytral disc. Specimens with very reduced and almost absent black patterns, as well as nearly completely melanistic specimens, have been observed, and might be not uncommon within all the species of the complex.
The endophallus (Fig. 5a) shows the typical organization already described for all the other groups (see Sassi 2018 for the terminology and figures) and regarded as an important trait in the delimitation of the genus. In this structure, the dorsal spicules are well-developed, with the apex aligned with the upper edge of the first sclerite in the folded-up structure. The fourth sclerite is broad, with wrinkled surface.
The vasculum of the spermatheca (Figs 5b–d) is C-shaped, with non-swollen lobes, the distal lobe slightly shorter than the basal one. The ductus is thin, rather long, and tightly coiled. The insertion of the ductus onto the bursa of the spermatheca is visibly sclerotized and elongated to form a pigmented sleeve.
Species treatments
description: Published as part of Sassi, Davide, 2025, Revision of the Metallactus minax Suffrian, 1866 species-group (Coleoptera: Chrysomelidae: Cryptocephalinae), pp. 71-86 in Zootaxa 5583 (1) on pages 72-73, DOI: 10.11646/zootaxa.5583.1.3, http://zenodo.org/record/14798002