Charidotella (Xenocassis), Spaeth, 1936

Sekerka, Lukas & Borowiec, Lech, 2015, Subgenera of Charidotella Weise with description of a new subgenus and species from Brazil (Coleoptera, Chrysomelidae, Cassidinae, Cassidini), ZooKeys 506, pp. 61-74 : 63-64

Taxon classification Animalia Coleoptera Chrysomelidae

Xenocassis Spaeth, 1936 Figs 12-13

Xenocassis Spaeth, 1936: 260; Hincks 1952: 342 (as subgenus of Charidotella ).

Type species.

Coptocycla amoena Boheman, 1855 by original designation.

Number of species.

15 (present paper).

Key to species.

Not yet proposed.

Range.

Mexico to Peru with most species in the Central America.

Distinguishing characters.

Xenocassis species can be easily separated from other subgenera by the small eyes covering only 2/3 of lateral sides of the head thus gena is well visible while all other subgenera have large eyes. In addition Xenocassis has nearly regularly circular body outline, weakly convex elytra with coarser punctation on lateral slope, and dorsum with ring pattern on the upper side. In extreme cases the ring can form a large discal spot or can be completely vanished thus whole dorsum is uniformly yellow.

Remarks.

So far Xenocassis was separated from other genera on the basis of the tarsal claws and general body shape. Windsor et al. (1992) were the first who noticed that all species have also small eyes in comparison to other Chardotella species. As a result they raised Xenocassis to genus in the provided key but unfortunately made no additional comments and their change was not accepted later (e.g. Borowiec 1999). We agree with them that the small size of the eye is diagnostic for Xenocassis and found that five species currently classified in the nominotypical subgenus should be transferred to Xenocassis based on this character. In addition we found that Xenocassis species are very variable regarding the size and presence of tarsal appendages. The genus was based by Spaeth (1936) on the outer claws of the metatarsi simple in both sexes, however, examination of extensive material revealed that even the type species, Charidotella amoena , could have the outer claws of the metatarsi with a large basal tooth. Similar situation was found in two other species we had extensive material to study - Charidotella (Xenocassis) ambita (Champion, 1894) and Charidotella (Xenocassis) puella (Boheman, 1855). In both the basal teeth showed variable size even within one population. While the size of the eye is constant. Some species of other subgenera have slightly smaller eyes than others thus they have gena visible but always very narrow while species of Xenocassis have gena covering approximately basal third of lateral side of the head.

We consider Xenocassis as subgenus of Charidotella as the size of the eye is found variable also in some other new world Cassidini genera, e.g. Charidotis Boheman, 1855 and Plagiometriona Spaeth, 1899.

Last catalogue, Borowiec (1999) listed 10 species in the subgenus Xenocassis . We have recently examined types of all species and found that one was wrongly assigned to Xenocassis . Coptocycla cingulata Boheman, 1862 (type seen in the Natural History Museum, London) was unknown to most authors and have been tentatively placed in Charidotella based on the original description ( Boheman 1862) and notes published by Champion (1894) in the Cassidinae volume of the Biologia Centrali Americana ( Borowiec 1989). It posses all characters of the genus Plagiometriona and is here transferred to it as Plagiometriona cingulata (Boheman, 1862), comb. n.

During examination of species placed in the nominotypical subgenus we found four which had small eyes and are here transferred to Xenocassis : Charidotella (Xenocassis) discoidalis (Boheman, 1855), comb. n., Charidotella (Xenocassis) incerta (Boheman, 1855), comb. n., Charidotella (Xenocassis) purpurea (Linnaeus, 1758), comb. n., and Charidotella (Xenocassis) myops (Boheman, 1855), comb. n. Types of all, with exception of Charidotella purpurea , were examined and are preserved in the Naturhistoriska Riksmuseet, Stockholm, Sweden. In addition Boheman (1855) described two more species in the same groups as abovementioned ones and we have strong feeling that they belong to Xenocassis too: Charidotella (Xenocassis) amoenula (Boheman, 1855), comb. n. and Charidotella (Xenocassis) cyclographa (Boheman, 1855), comb. n. Unfortunately, we were not able to locate their type specimens thus the transfer is tentative, based on primary descriptions according to which the species should have the circular body shape, the annulus on upper side of the elytra, and coarser punctation on the lateral slope of elytral disc like other Xenocassis species.