Metallactus abstersus D. Sassi 2025, comb. nov.
Creators: name: Sassi, Davide
Publisher: name: Zenodo
Year: 2025
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Chrysomelidae
Metallactus
Metallactus abstersus

description: Metallactus abstersus (Suffrian, 1866) comb. nov.
(Figs 2; 5d; 6b)
Scolochrus abstersus Suffrian, 1866: 133; Clavareau, 1913: 88 [Griburius] (catalogue); Blackwelder, 1946: 639 [Griburius] (catalogue). = Metallactus incultus Suffrian, 1866: 358; Clavareau, 1913: 93 (catalogue); Blackwelder, 1946: 641 (catalogue). Syn. nov.
Types. As regard Scolochrus abstersus, Suffrian (1866) did not mention the number of specimens under study, but he reported that he could examine only females, and the material (hosted in MNHUB) was collected by Virmond in Brazil. One single specimen matching the original description was tracked down in MNHUB. Curiously, and once again, the specimen turned out to be male. For the same reasons pointed out concerning the typification of M. minax (see above), it seemed reasonable to assume that Suffrian erroneously believed the likely single available specimen to be a female. Therefore, the specimen in MNHUB, whose external habitus perfectly matches the original description, has been designated as the lectotype. The typification was made as follows. LECTOTYPE: ♂, glued, aedeagus glued on the same card, abdomen glued on a separate card, // “abstersus Suffr. * Brasil Virm.” [blue label, handwritten] // “24027” [white label, printed] // “ Griburius abstersus (Suffrian, 1866) (Scolochrus abstersus) LECTOTYPUS D. Sassi des.” [red label, printed] // “ Metallactus abstersus (Suffrian, 1866) D. Sassi det. 2024” [white label, printed] // (MNHUB). The information on the original label, matches the registration data from the old catalogue of the MNHUB (“24027 [Scolochrus] abstersus Suffr. * 1. Brasil, Virmund.”).
Regarding Metallactus incultus, Suffrian once again does not indicate the exact number of specimens he studied, but states that he saw only females. From the description provided, it can be inferred that there were at least three. Additionally, he lists MNHUB and NMV, as well as the Clark collection, currently housed in BMNH, as depositories of the material. My research has located four syntypes, all females: one in MNHUB, one in BMNH, and two in NMV. The Berlin specimen matches perfectly with the description of the coloration that Suffrian seems to consider as 'typical,' and for this reason, it has been designated as the lectotype of the species. The information on the original label, matches the registration data from the old catalogue of the MNHUB (“23982 [Metallactus] incultus Suffr * 1. [Brasil], v. Olf."). The specimens from London and Vienna correspond, with some minor approximations, to what the German entomologist reports as variations in colour (essentially a reduction of the black elytral pattern, up to completely yellow elytra). These three specimens have been designated as paralectotypes. Regarding the labels on the specimens from Vienna, which do not match what Suffrian (1866) reported in the original description, it should be emphasized (as already pointed out above) that this issue pertains to all the material from Vienna used by Suffrian in his monograph. This matter has been discussed multiple times in previous works, to which the reader is referred for details (Sassi 2018, 2022). The typification was made as follows. LECTOTYPE: ♀, pinned, // " incultus Suffr.* Brasil v. Olf." [blue label, handwritten] // "23982" [white label, printed] // “ Metallactus incultus Suffrian, 1866 LECTOTYPUS D. Sassi des.” [red label, printed] // “ Metallactus abstersus (Suffrian, 1866) D. Sassi det. 2024” [white label, printed] //. (MNHUB). The information on the original label, matches the registration data from the old catalogue of the MNHUB (“23982 [Metallactus] incultus Suffr * 1. [Brasil], v. Olf.”). PARALECTOTYPES (3): 1♀, pinned, // “brasilia” [white label, handwritten] // “162” [blue label, handwritten] // “E. Coll. Chev. t ” [white label, printed] // “ Met incultus ” [white label, handwritten] // “a D. Saffrian. [sic!] determinat.” [white label, handwritten] // “67.56” [white label, printed] // (BMNH); 2♀, pinned, // “Ytaranga Brasilien Natterer” [white label, printed] // (NMV). All paralectotypes labelled: “ Metallactus incultus Suffrian, 1866 PARALECTOTYPUS D. Sassi det.” [red label, printed] // “ Metallactus abstersus (Suffrian, 1866) D. Sassi det. 2024” [white label, printed] //.
Type locality. “ Brazil ”.
Further material examined. None.
Distribution. Brazil.At present, it seems impossible to identify the exact geographic location of the only locality mentioned on the labels of the material preserved at NMV (Ytaranga). However, it is reasonable to assume that this is an old toponym from southern Brazil, possibly from the state of São Paulo, where it is known that Natterer conducted extensive research and collected a large amount of material (Schifter, 1993).
Comparative notes. For its dorsal coloration, Metallactus abstersus closely resembles some species in the M. kollari (Perty, 1832) species-group (Sassi 2018), particularly in specimens where there is a reduced black pattern on the elytra, as sometimes seen in M. dodecastictus Suffrian, 1866. However, in the species of the kollari group, the head, legs, and ventral parts typically have extensive or predominantly yellow colouration while in M. abstersus the ventral parts and the legs are completely black, and the head almost entirely black, sometimes with a hint of a dirty yellow spot on the lower part of the clypeus. Conversely, the upper lip is consistently a rather bright yellow, contrasting sharply with the dark colour of the rest of the head. This combination of colours is not found in other Metallactus species-groups. The only species in the kollari group with entirely black head and legs is M. languidus Suffrian, 1866, but here the sides of the abdomen are bordered with yellow, and the elytral pattern observed so far is clearly different, being characterized by a series of small, rounded black spots (up to six), arranged in two rows on each elytron. Again, in M. albifrons Suffrian, 1866 the abdomen and the legs are completely black, but the frons is extensive yellow. Anyway, the morphology of the aedeagus is always decisive, as the large tubercle on the ventral face of the median lobe of the aedeagus, characteristic of species in the minax group, is never observed in the kollari group of species. The combination of the chromatic characters mentioned above (legs, head, upper lip and ventral parts) allows this species to be closely aligned with M. minax, whose affinity is especially evident due to the morphology of the aedeagus and the shape of the anal depression in the male. Males of M. abstersus can be distinguished from those of M. minax not only by the different color pattern but also by the shape of the median lobe of the aedeagus. In particular, the curvature of the median ventral bulge, whose apical profile in lateral view is distinctly convex in M. abstersus, whereas it is concave in M. minax. Lastly, the shared colour pattern with females previously assigned by Suffrian to a different taxon (M. incultus), and the substantial similarity in overall appearance, further justifies proposing the following synonymy:
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 77-78, DOI: 10.11646/zootaxa.5583.1.3, http://zenodo.org/record/14798002