Dichotrachelus sondereggeri, Germann, 2011

Germann, Christoph, 2011, Review of the Dichotrachelus alpestris STIERLIN, 1878 species group with evidence for a species complex of D. augusti F. SOLARI, 1946, and D. sondereggeri sp. nov. from Switzerland (Coleoptera, Curculionidae), Contributions to Natural History 17, pp. 1-21 : 5-8

Dichotrachelus sondereggeri sp. nov.

( Figs 1–4 , 17, 21, 24 , 29–32 )

Holotype ♂: Switzerland, Grisons, Valposchiavo, above Cavaione, Corn dal Solcun , Swiss coordinates: 804.200 / 126.229, 2480 m a.s.l., sifting mosses, 2. 7. 2009, leg. C. Germann. Red label: Holotype Dichotrachelus sondereggeri sp. nov. ( NMBE) .

Paratypes: 8 specimens. 2 ♂♂ and 3 ♀♀, same indications as holotype. Red labels: Dichotrachelus sondereggeri sp. nov. des. C. Germann 2011 (1 ♂, 1 ♀ cCG; 1 ♂, 1♀ NMBE; 1 ♀ NMLU); 1 ♀, (same data as holotype, cCG) is kept in 90% ethanol for potential DNA extraction ; 1 ♀ (same data as holotype, cCG) consists only of an abdomen (including elytra and all female genitalia, as well as fragments of 33 eggs) ; 1 ♀ Suisse, Grisons, s/ Cavajone [sic!], 18. 7. [19]94, pied rochers 2050 –2100 m, leg. Cl. Besuchet. Dichotrachelus gr. alpestris STIERLIN det. Osella 1985 ( alpestris n sp.?). Red label: Dichotrachelus sondereggeri sp. nov. ( MHNG, coll. G. Toumayeff).

Size: 3.8–4.9 mm (♂ 3.8–4.5 mm, ♀ 4.4–4.9 mm)

Body colour: Black to dark brown, antennae and tarsi reddish brown.

Head, rostrum and antennae: Head globose, irregularly punctate, raised broad dark brown scales on the front. Thinner scales from the epifrons up to the antennal scrobes. Eyes weakly protruding, almost circular. Rostrum about twice as long as wide (L/B): 1.8–2.1 (♂ 1.8–2.0, ♀ 1.8–2.1). The epifrons of the rostrum is shiny and irregularly striato-punctate. The rostral apex is glossy and shining, irregularly punctate and with raised setae. Antennal scrobes are visible from above. Antennae are strong and long, inserted before the middle of the rostrum. Antennal scape (L/B: 6.5) slender in its first third, then continuously broadened to three times its basal width. Bright setae and dark brown scales arise from the broad half of the antennal scape. First segment of antennal funiculus more than twice as long as wide, the following segments as follows (L/B): 2 nd: 1.3, 3 rd to 5 th: 1.0, 6 th: 0.85 and 7 th: 0.6. The antennal club (L/B: 1.9) twice as wide as the last antennal segment, consisting of three visible segments.

Pronotum: Index (L/B): 1.06–1.14. Somewhat longer than wide, laterally modestly rounded, widest in the middle. Vestiture consisting of adherent and raised, strong, mainly dark brown scales, several light brown scales are intermixed.

Elytra: Index (L/B): 1.62–1.72. Base slightly broader than pronotum, subelliptical, without humeral callus (apterous), cone-shaped from the base on, widest shortly behind the middle. Uneven intervals including suture elevated, wider than the deeply punctate striae. Suture markedly bulged just before the decline of the elytra (best visible in lateral view). Integument consisting of two types of scales: semi-raised, short and rounded (often globular) scales, and raised scales, which are up to three times as long as wide. Scales are mostly dark brown; several patchily arranged light brown scales are intermixed.

Legs: Strong and slender, three visible tarsal segments of about the same size, claw segment almost as long as the three visible tarsal segments, claws simple.

Aedeagus ( Fig. 17 ): Apex of aedeagus abruptly attenuated and laterally moderately constricted before tip, fore margin weakly rounded.

Spiculum ventrale and spermatheca ( Figs 21, 24 )

Sexual dimorphism: Elytral shape of male laterally more parallel (in females slightly convex). Fifth sternite of males shorter (B/L: 1.9–2.0) than females (1.0–1.3).

Differential diagnosis: The most conspicuous traits of D. sondereggeri sp. nov. are the elongated cone-shaped elytra with their maximal width behind the middle ( Figs 2–3 ), the long slender legs and the conspicuous apex of the aedeagus ( Fig. 17 ). The presumably closest relative based on morphological characters is D. augusti , sharing the conspicuous strongly constricted apex of the aedeagus. To differentiate the species of the alpestris species group, all three species are keyed in the following. Although the shape and colour of the scales are often used for differential diagnoses in Dichotrachelus , this trait should be used only with care as considerable variation was found within the large series of specimens of D. alpestris from all over the distribution area. The spiculum ventrale of D. alpestris allows the unambiguous separation from all the other species of the group with its conspicuous rectangular branches ( Fig. 23 ), whereas those of D. sondereggeri sp. nov. and D. augusti are very similar. If spermathecae are compared, the available specimens of D. augusti all show a thicker plump cornu, whereas those of D. sondereggeri sp. nov. and D. alpestris are steadily tapered and thus more gracile ( Figs 24–26 ).

Figures

Fig. 1: Dichotrachelus sondereggeri sp. nov., male holotype (drawing by H.-P. Wymann).

Figs 2–4: Dorsal and lateral views: 2) Dichotrachelus sondereggeri sp. nov. from Corn dal Solcun, male; 3) Ditto female; 4) Ditto male.

Figs 17–26: Male and female genitalia. 17–20: Tip of aedeagus: 17) Dichotrachelus sondereggeri sp. nov. from Corn dal Solcun; 18, 19) forms II (Val Ferret), and III (Col de Balme) of D. augusti species complex; 20) D. alpestris from Anzeindaz. 21–23: Spiculum ventrale: 21) D. sondereggeri sp. nov. from Corn dal Solcun; 22) D. augusti form II from Val Ferret; 23) D. alpestris from Anzeindaz. 24–26: Spermatheca: 24) D. sondereggeri sp. nov. from Corn dal Solcun; 25) D. augusti form II from Val Ferret; 26) D. alpestris from Anzeindaz.

Figs 29–32: Different stages of Dichotrachelus sondereggeri sp. nov.: 29) last instar larva just before pupation; 30) pupa ventral view; 31) pupa dorsal view; 32) freshly hatched imago. Fotos: C. Germann.