The species of Timarcha Samouelle, 1819 described by Linnaeus (Coleoptera, Chrysomelidae)

Abstract Linnaeus described five species presently included in the genus Timarcha: Chrysomela goettingensis, Tenebrio caeruleus, Tenebrio laevigatus, Tenebrio latipes, and Tenebrio rugosus. After a study of the relevant material, the identity of these species has been established. The following synonyms are proposed or confirmed: Timarcha goettingensis (Linnaeus, 1758) = T. latipes (Linnaeus, 1767), syn. nov.; Timarcha caerulea (Linnaeus, 1758), comb. nov. = T. balearica Gory, 1833, syn. nov. = T. balearica Pérez Arcas, 1865, syn. nov.; Timarcha rugosa (Linnaeus, 1767) = T. scabra (Olivier, 1807), syn. conf. = T. generosa Erichson, 1841, syn. conf.; Timarcha laevigata (Linnaeus, 1767) = T. tenebricosa (Fabricius, 1775), syn. conf.. The type of Tenebrio caeruleus is a Chrysomelidae currently belonging to genus Timarcha and therefore can no longer be considered a Tenebrionidae (Helops caeruleus) nor the type species of genus Helops. For the sake of nomenclatural stability, an application to the International Commission on Zoological Nomenclature to change the relative precedence of Timarcha caerulea and retain usage of T. balearica will be made. An application to change the relative precedence of Timarcha laevigata has been submitted, which would lead to the conservation of usage of T. tenebricosa as valid. Lectotypes are designated for Chrysomela goettingensis, Tenebrio latipes, Tenebrio caeruleus, Timarcha balearica Gory, T. balearica Pérez Arcas, Tenebrio rugosus, Chrysomela scabra, Timarcha generosa, Tenebrio laevigatus, and Chrysomela tenebricosa. For each of the valid species the diagnosis, distribution, and host-plant data are reported.


Introduction
The taxonomy of the genus Timarcha Samouelle, 1819 (Coleoptera, Chrysomelidae) is among the most challenging of all Palaearctic chrysomelids because: i) the types were rarely consulted by authors, and ii) there exists a high variability in traits as size, sculpture and form of the pronotum (Petitpierre 1970;Tiberghien 1971;Gómez-Zurita 2008;Kippenberg 2010). Therefore, a revisionary work on this genus is required (Daccordi et al. 2020).
As a starting point for the revision of the genus Timarcha, we have studied the species authored by Carl Linnaeus. He described five species presently belonging to this genus. They are Chrysomela goettingensis Linnaeus, 1758, Tenebrio caeruleus Linnaeus, 1758, Tenebrio laevigatus Linnaeus, 1767, Tenebrio latipes Linnaeus, 1767, and Tenebrio rugosus Linnaeus, 1767. One of us (MAAZ) studied and photographed the types of T. latipes and T. laevigatus in the collection of the Linnean Society of London. As well, consultation of photographs of Linnean types on the website of the Linnean Collections (http://linnean-online.org/) of the Linnean Society of London, together with a study of type specimens of other nominal species in other museums, led us to reconsider the availability and nomenclatural status of the five species of Timarcha described by Linnaeus.

Material and methods
Measurements of body length were made using the ocular grid of a Lomo MBS-10 binocular microscope at 10× magnification. Body size was considered the total length of the specimen from the anterior region of head to the apex of elytron. Photographs of type specimens of Tenebrio laevigatus and T. latipes were taken with a Canon EOS 7D camera attached to a MP-E 65 mm f/2.8 1-5× macro lens. Photographs of type specimens of Chrysomela goettingensis, Tenebrio caeruleus, and T. rugosus were kindly provided by Linnean collections staff (The Linnean Society of London) and of Timarcha balearica Gory, 1833 by Antoine Mantilleri (MNHN). Types, and their parts, of Timarcha balearica Pérez-Arcas, 1865, T. scabra (Olivier, 1807), and T. generosa Erichson, 1841 were photographed with an Olympus Stylus TG-3 digital compact camera. Photographs of other specimens or their parts were done with a Canon EOS 550D attached to a bellows with a Schneider Componon-S 50mm f/2.8 objective. Combine ZM was used for resolving the stack of photos.
The methodology to name the vestiture under of the tarsi I-III, to dissect the sclerites of endophallus, and to inflate the endophallus is explained by Daccordi et al. (2020).
In the treatment of type material from the collection of Carl Linnaeus, we have followed Recommendation 73F (International Commission on Zoological Nomenclature 1999) and have designated "a lectotype rather than assume a holotype". The designation of lectotypes in this paper has been made by the three authors jointly, unless otherwise indicated in the labels of the types.
Host plants are given using their valid names. If a name, now a synonym, was originally mentioned, this follows the valid name between round brackets. Plant nomenclature follows APG IV (2016) for families and The Plant List (http://www.theplantlist.org) for genera and species names.
The material examined is housed in the following collections (curators mentioned between round brackets):
Diagnosis. Males: 7.4-12.6 mm (lectotype of T. goettingensis: 8.7 mm; Fig. 1); females: 8.4-14.5 mm (lectotype of T. latipes is an unextended specimen measuring 8.4 mm; Fig. 2). Black or black with bluish luster (Fig. 3). Highly variable species in brightness, puncturation, form of the pronotum and elytra, and size. Sides of the pronotum regularly, slightly curved or almost straight, with the widest point in the basal third or at base, never cordiform, completely margined or with lateral margins obliterated at different extent (Fig. 4). Puncturation on the pronotum and elytra dense, regular, heavily or weakly marked, usually stronger on the elytra, not or conspicuously vermiculated (Figs 3,4). Mesoventrite variable with apophysis a bit prominent, slightly forked, or more or less emarginated or almost straight, never clearly bituberculated. Vestiture of the female tarsi: (1, 1, 1/3-3/4; 1, 1, 1/3-3/4; 1, 4/5-1, 1/2-3/4). The aedeagus is slender and progressively narrowed towards the apex in dorsal view and regularly curved in side view (Fig. 5). Sclerites of the internal sac of the aedeagus (Fig. 6) with a paired phanera in romboid form, which is an important diagnostic character to separate this from other closely related species. The inflated endophallus of an approximate locotype (coming near Göttinga in central Germany) (Fig. 7) is shown. A number of species and subspecies, whose taxonomical rank has yet to be studied, have been described in association with this species (   Comments. Timarcha balearica was described for the first time as figure 8 in planche 49 (Gory 1833). Later, Gory (1844: 300) published a text description (see Bousquet 2016 for exact publication dates).
Distribution. Most of Europe, from northern Spain to Great Britain and Ireland, eastwards to Georgia, Azerbaijan, and Asiatic Turkey; not recorded in Scandinavia (Gómez-Zurita and Kippenberg 2010).

Discussion
The difficult task of studying the types of old species has been greatly facilitated with the quick access to high-quality images. As a result, it is now easier for taxonomists to verify the status of old synonyms or interpretations which were based upon very short, generalized descriptions. The high-quality images of the types in the Linnaean collections have proven extremely useful for the zoological community. In addition, most museums and their curators are willing to help with search for and loan of types, which can facilitate taxonomic work. Incorrect species concepts, not based on the examination of name-bearing types, have sometimes been maintained despite the identity of extant type material, which has been carefully cared for and maintained for many years for the benefit of science.
In the case of genus Timarcha, whose revision is very necessary, the slow and sometimes difficult work of consulting types has become absolutely necessary, as various authors have made different interpretations for a long time. Although historical misinterpretations of T. laevigata and T. latipes have ascribed these to different North African species or even to both sexes of the same species, these two species are actually two very different European species. Also, T. caerulea is revealing, as it was considered a Tenebrionidae, when in actuality the type is clearly a male of the genus Timarcha, identical to T. balearica (Chrysomelidae).
The main synonyms presented here can be summarized as follows: