Stolas silbermanni ( Boheman, 1850 )

Sekerka, Lukáš, 2016, Taxonomic and nomenclatural changes in Cassidinae (Coleoptera: Chrysomelidae), Acta Entomologica Musei Nationalis Pragae 56 (1), pp. 275-344 : 335-336

Stolas silbermanni ( Boheman, 1850) stat. restit.

Mesomphalia Silbermanni Boheman, 1850: 269 (original description).

Mesomphalia vicina Boheman, 1850: 329 (original description), syn. nov.

Type localities. Mesomphalia silbermanni : ‘Buenos Ayres’; M. vicina : ‘ Rio Grande Brasiliae’ .

Type material examined. Mesomphalia silbermanni : LECTOTYPE (present designation): ♀, pinned: ‘E. Coll | Chevt. [w, p, cb] || Type [w, p, s, c, rf] || 13. [w, p, s] || Silbermannii | Ch Bayres [w, hw by Chevrolat, s] || B. Ayres | Silbermann [g, hw by Chevrolat, s] || Mesomphalia | silbermanni (Chv) | Bhn Bayres [w, hw by Chevrolat, s] || 67·56 [w, p, s]’ ( BMNH).

Mesomphalia vicina : SYNTYPE: ♀, pinned (teneral specimen): ‘E. Coll. | Laferté [w, p, s] || Cyrtonota | Vicina Reic | Brasil: mer: Rio G: de [g, hw, s, original Dejeanʼs label] || 67·56 [w, p, s]’ ( BMNH).

Remarks. BOROWIEC (1999a) synoynmized Mesomphalia silbermanni with Stolas festiva (Klug, 1829) probably based on Spaethʼs unpublished manuscript. However, the type has gibbose elytra, which are weakly convex in S. festiva and M. silbermanni is more similar to other species of this group. Stolas tumulus ( Boheman, 1850) and S. ignita ( Boheman, 1850) have also gibbous disc of elytra but differ in much larger size with length over 14 mm (12 mm in M. silbermanni ) and broader and less declivous explanate margin of elytra. The most similar are S. vicina and S. paranensis ( Spaeth, 1928) , both having similar size but the latter has distinctly less convex elytra. Strictly comparing the types of M. silbermanni and S. vicina the latter has less convex elytra and lower reticulation on disc enclosing larger fields while M. silbermanni has more elevated reticulation enclosing smaller fields. However, the syntype of S. vicina is not fully sclerotized and the top of elytra was damaged during pinning, somewhat disfiguring the convexity. Except of the convexity and size of the fields enclosed by reticulation the two taxa are nearly identical and they are probably conspefic. Species of the S. festiva group are quite variable and it is not uncommon that local populations of one species differ in density of reticulation on elytra and also to some extent in their convexity, therefore I synonymize the two taxa. Since both taxa were described in the same publication I followed the Principle of the first reviser ( ICZN 1999: Article 24.2) and chose the name S. silbermanni as the valid one because its type is better preserved.

BOHEMAN (1850) described M. silbermanni presumably from a single specimen from the collection of Chevrolat. However, he did not explicitly state whether he had one specimen or more, but only provided a single length measurement. It is thus probable that more specimens might exist as Chevrolatʼs collection was sold in various auctions and specimens are spread among number of institutions. In order to conserve the identity of this species I hereby designate the BMNH specimen as lectotype. It undoubtedly came from the collection of Chevrolat as it possesses his original handwritten labels and perfectly agrees with the primary description.

Distribution. Argentina, Brazil: Rio Grande do Sul ( BOHEMAN 1850, BOROWIEC 2009c).