Silvacalles cedroensis ( Kulbe, 2000 ) comb., 2010

Stüben, Peter E. & Astrin, Jonas J., 2010, Molecular phylogeny in endemic weevils: revision of the genera of Macaronesian Cryptorhynchinae (Coleoptera: Curculionidae), Zoological Journal of the Linnean Society 160 (1), pp. 40-87 : 61

Silvacalles cedroensis ( Kulbe, 2000) comb.

nov. (formerly: Acalles , Dendroacalles ) – La Gomera

Silvacalles lunulatus ( Wollaston, 1854) comb. nov. (formerly: Acalles , Dendroacalles ) – Madeira

Silvacalles nubilosus ( Wollaston, 1864) comb. nov. (formerly: Acalles ) – Tenerife (including type locality), La Palma

Tagasastacalles subgen. nov.

Type species: Acalles hakani Roudier, 1954

Silvacalles (Tagasastacalles) hakani hakani ( Roudier, 1954) comb. nov. (formerly: Acalles ) – Tenerife

Silvacalles (Tagasastacalles) hakani tagasaste (Stüben, 2000) comb. nov. (formerly: Acalles ) – La Palma (including type locality), El Hierro?

Silvacalles (Tagasastacalles) pedestris (Stüben, 2000) comb. nov. (formerly: Acalles ) – La Palma (including type locality), Tenerife, El Hierro, La Palma

Tolpiacalles subgen. nov.

Type species: Acalles (Tolpiacalles) tolpivorus Germann & Stüben, 2006

Silvacalles tolpivorus ( Germann & Stüben, 2006) comb. nov. (formerly: Acalles ) – La Gomera

The taxa of this new genus belong mainly to the groups of Acalles instabilis and Acalles tagasaste ,

which have already been revised ( Stüben, 2000a:

35–46). All species of this genus inhabit the thermo-

Canarian belt above 400 m, namely the thermophilous shrub forest (‘bosque termófilo’) on the Canary

Islands and the Canarian and Madeiran laurel forest.

Description

Size: 2.0– 7.5 mm.

Head: The puce, shiny rostrum of the ♂ two-thirds and of the ♀ three-quarters as long as pronotum (shorter only in Silvacalles tolpivorus ). The rostrum of the ♀ more slender and fine, rostrum of the ♂ slightly more robust and with more strongly punctures. The antenna unicoloured puce.

Pronotum: About as wide as long and the outline almost always strongly ‘bellied’ rounded; mid-groove either – as in most of the species – completely absent or – as in only a few species – at most with a very slight depression. Disc of pronotum with only a small, isolated pair of tufts of bristles (often only consisting of a few dark bristles sticking out vertically); on the front margin with a collar of long bristles sticking out vertically and arranged more densely in the middle. Outline of pronotum regularly rounded at all sides; disc of pronotum often convex. However, the pronotum coasts down towards the front margin flatly, often ‘delta-like’, with a strong lateral depression/ constriction next to the front margin. The contrasting colouring of the elytra (especially in Silvacalles nubilosus ) is also continued on the pronotum even if large-scaled, light marks and fascia are absent.

Elytra: Elongated, canoe-like; 1.34¥ (1.23¥ in S. pedestris ) to 1.60¥ as long as wide; widest c. in the middle; outline laterally slightly and towards the elytral slope rounded more strongly oval. Without shoulders next to the base; however, the sixth interval sometimes slightly protruding tooth-like; apex of elytra strongly elongated, which causes – similarly to the genus Dendroacalles – a ‘canoe-like’ habitus. Next to the apex with a slight lateral depression. On the second and fourth interval with little bristled humps and knobs, which are definitely not as steeply erected and high as in Dendroacalles s.s.; the colouring of the elytra extremely variable interspecifically as well as intraspecifically. Elytral slope with an almost triangular, dark mark that is extended to a broad, fuliginous fascia in Silvacalles hakani tagasaste .

Legs: Long, the front femur projecting above the front margin of pronotum; legs obscurely annulated; the femur mostly with two, the tibia with one obscure dark ring. Femur with raised, light, slender bristles; the outer edge of tibia with bristles sticking out vertically.

Venter: First abdominal sternite very long, longer than the second, the latter as long as or longer than both following sternites combined, fifth sternite again longer.

Aedeagus: Endophallus with an often tiny, fork-like structure (degenerated or lacking in Silvacalles nubilosus , Fig. 36B ) that is terminated towards apex by a sclerotized (transparent and trapezoidal) plate that is mostly clearly wider than long in the species of the subgenus Silvacalles s.s. ( Fig. 6B ). Only S. tolpivorus has a clearly different, distinctive, ‘goblet-like’ structure of the internal sac ( Fig. 7B ). The three species of the subgenus Tagasastacalles – only with the fork-like structure of the endophallus ( Fig. 8B ) – also belong to this genus.

Differential diagnosis: The species of the new genus Silvacalles can be easily discriminated from the species of the new genus Aeoniacalles (described above): the latter have a sickle-like structure at the basal ends of the forked structure of the endophallus ( Fig. 5B ) which is absent in the genus Silvacalles .

Both species within the subgenus Silvacalles and the species within the genus Dendroacalles inhabit the dense laurel forest of the Canaries and Madeira. Therefore, confusion during determination seems possible. However, the specimens of Dendroacalles are larger (3.5–7 mm) than those of Silvacalles s.s. (2–3 mm – S. mundus and S. nubilosus 5 mm at most). Moreover, the species of Dendroacalles have two plates above the forked structure of the endophallus ( Figs 3B, 4B ), whereas in Silvacalles s.s. these structures form a single, connected, trapezoidal, or square-like plate ( Fig. 6B ). Silvacalles nubilosus has a single, almost square-like, very thick, and hardly transparent plate as well, and the terminating, basal, fork-like structure is lacking or has been reduced ( Fig. 36B ). See also the ‘Key to the genera and subgenera of Macaronesian Cryptorhynchinae’.

Figures

Figure 36. A, Silvacalles nubilosus (in dorsal view). B, aedeagus in ventral view (left), endophallus (right). C, Ixanthus viscosus Griseb., the host plant of S. nubilosus.

Figures 2–22. Morphological, biological, and ecological comparison of the genera and subgenera of Macaronesian Cryptorhynchinae along with the respective sections of the tree; (TS) = type species. Figures 4E and 5E show a section of the tree that results when 16S sequences for Aeoniacalles aeonisimilis* and Dendroacalles euphorbiacus* are excluded.