Dichotrachelus sonjae, Szallies & Germann, 2025

Szallies, Alexander & Germann, Christoph, 2025, A new Dichotrachelus Stierlin from Val Grande (Piemonte, Italy) (Coleoptera, Curculionidae) with comments on biogeography and evolution of high alpine species of the genus, Alpine Entomology 9, pp. 29-36 : 29-36

Dichotrachelus sonjae sp. nov.

Holotype.

Male “ 440 _ 24.3 ITALIA, Piemonte, Valle Vigezzo, Druogno, unterh. Pizzo Nona , 46.09943, 8.41411, 1950 m, GS Moos Blockhalde, 31. 10. 2024, leg. C. Germann ” ( NMB).

Paratypes.

50 ex. “ 440 _ 24.3 ITALIA, Piemonte, Valle Vigezzo, Druogno, unterh. Pizzo Nona , 46.09943, 8.41411, 1950 m, GS Moos Blockhalde, 31. 10. 2024, leg. C. Germann ” . – 22 ex. “ 440 _ 24.4 ITALIA, Piemonte, Valle Vigezzo, Druogno, unterh. Pizzo Nona , 46.09942, 8.41492, 1910 m, GS Moos Blockhalde, 31. 10. 2024, leg. C. Germann ” . – 4 ♂, 2 ♀ “ Druogno, Pizzo Nona Nordseite 2000 m, 9. 8. 2024, leg. Szallies ” . – 15 ♂, 38 ♀ “ Druogno, Pizzo Nona Nordseite 2000 m, 31. 10. 2024, leg. Szallies ”. (cCG, cAS, cMM, cRM, NMB, NMBE) .

Description.

Size: 3.3–4.2 mm (♂ 3.3–4.0 mm, ♀ 4.0– 4.2 mm), Figs 1–4 , 9 , 11–15 .

Body colour: Black to dark brown, antennae and legs reddish brown. Head, rostrum and antennae: Head globose, irregularly punctate, raised broad dark brown scales on frons. Thinner, clubbed scales on epifrons up to antennal scrobes. Eyes weakly protruding, oval.

Rostrum about twice as long as wide (L / B): 1.9–2.0; epifrons of rostrum shiny and irregularly striated-punctuated; rostral apex glossy and shiny, irregularly punctuated and with erect bowed setae; antennal scrobes visible from above, diverging towards eyes, in lateral view bowed downwards, limited by a horizontal ridge extending from lower end of eyes to lower limit of scrobes.

Antennae strong, inserted on last third of rostrum; antennal scapes (L / B: 6.5) slender in its first third, then continuously broadened to three times as wide as width at base; dark brown, with clubbed scales from broad half of antennal scape; first segment of antennal funicles more than twice as long as wide, following segments as follows (L / B): 2 nd: 1.6, 3 rd to 7 th: 1.0; antennal clubs (L / B: 2.1) twice as wide as last antennal segment, consisting of three visible segments.

Pronotum: Index (L / B): 1.12–1.14. Longer than wide, laterally weakly rounded, widest at middle, at fore and hind margins only weakly constricted; vestiture consisting of adherent and raised strong, clubbed mainly dark brown scales with several light brown scales intermixed, especially along middle.

Elytra: Index (L / B): 1.53–1.71. Base slightly broader than prothorax, subelliptical, without humeral calli, oval, widest along middle; uneven intervals including suture weakly elevated, wider than deeply punctuated striae; elytral disc slightly flattened (lateral view); integument covered with two types of scales: semi-raised, short and rounded or oval scales, and raised clubbed scales, up to twice as long as wide. Scales mostly dark brown; several patchily arranged light brown scales intermixed.

Legs: Strong and slender, with elongate, bowed, dark brown scales and thinner light brown scales; apex of tibiae with a pair of lobal formed spines, reminding of spurs, with their tips subparallel projecting ventrally (Figs 14 , 15 ). Three visible tarsal segments, first and second of same length, third 1.5 × as long as wide and distally bilobed, fourth tiny, hardly visible, claw segment twice as long as third one, claws simple.

Aedeagus: Base of penis evenly sclerotized; ostium of penis oval and discreet, twice as long as broad. Penis, towards distal tip, with basal half covered by a thin translucent sclerotized sheath; at anterior end of ostium, penis with long dagger-like apex (Figs 3 , 4 ); internal sclerite with small central doublet and split inner arms with thick and bowed anterior arms surrounding central part. Encompassing sheath, valves forming a double lobed structure reminding of butterfly wings, as best seen in lateral view of single “ valve ”; sheath of internal sclerite evenly rounded, carrying lateral sclerites at middle of each of valves (Figs 11–13 ).

Female genitalia: Sternite VIII (Fig. 18 ), spermatheca (Fig. 20 ) and gonocoxites (Fig. 22 ).

Sexual dimorphism: Elytral shape of male laterally parallel (in females slightly convex), spurs of tibiae in males more pronounced than in females. Fifth sternite of males more broadly rounded apicad than in females, with a more pointed arch-like apical margin (Fig. 9 ).

Derivation of the name: In deep gratitude and love the name of the new species was given by the first author to honor his wife Sonja, in compliance with provisions outlined by Lohse (1964).

Biology.

While collecting the adults of D. sonjae , we encountered several larvae hidden in the dense moss cushions in the scree slope in late autumn (Figs 24 , 25 ). We were surprised to find not only large larvae in the last larval stage (Fig. 26 ) but also tiny larvae in the first larval stage, hardly one millimeter in length (Fig. 27 ).

Differential diagnosis.

D. sonjae is morphologically most similar to D. lepontinus , described from Cimalmotto (Ticino, Switzerland) and differs mainly in the unique dagger-like tip of its penis (Figs 3 , 4 compared to 7, 8). Females may be separated by their spermathecae and sternites VIII. The edged projection at the base of the spermatheca of D. lepontinus (Fig. 21 ) is totally absent in D. sonjae (Fig. 20 ).

The morphological differences between D. sonjae and D. lepontinus are as follows: Shape of elytra in males more elongate oval, shoulders more reduced, more slender in D. sonjae (Figs 1 , 2 ), elytra wider oval and wider at shoulders in D. lepontinus (Figs 3 , 4 ), pronotum in both sexes little more rounded laterally in D. sonjae (Figs 3 , 4 ). Legs, femora stronger and thicker in D. sonjae . Erect scales on elytra and pronotum are a little thicker and stronger in D. sonjae than in D. lepontinus . In females, both species have a very narrow sternite VIII, in D. sonjae the plate is wider (Figs 18 , 19 ).

Remarkably, both species share a heavy sclerotization of the aedeagal tubular base, with a distinct delineation marked by the ostium, occurring amongst Dichotrachelus of the Alps only also in D. rudeni Stierlin, 1853 and D. imhoffi Stierlin, 1857 . The ostium of the penis in D. sonjae is much more reduced in length than in D. lepontinus , to an oval orifice nearly twice as long as wide, while in D. lepontinus the ostium is much longer with clearly weaker sclerotization of the aedeagal base.

Another species similar to D. sonjae is D. meregallii , which appears to be the only other Dichotrachelus species sharing the double (duplex) lobal spurs with D. sonjae and D. lepontinus . In D. meregallii the posterior tibiae possess only one apparent single spur that is markedly larger and longer than any of the duplex spurs of the other tibiae of D. lepontinus and D. sonjae , respectively. This seemingly single spur is in fact consisting of two separate ones (magnification 100 ×). Notably, one specimen of D. meregallii from a population at unusually low altitude (Valle di Lanzo, Ceres), exhibits intermediate states of spur fusion on the meso- and faintly on the protibiae.

Another species preferring rocky habitats in a high alpine environment is Dichotrachelus augusti Solari, 1946 , which shares the slender and long tibiae with D. sonjae . It also has spurs on its tibiae, but these are singular, fine, short, and pointed. The basal part of its aedeagus is weakly sclerotized, but more so than in D. meregallii .

Molecular data.

Mitochondrial genetic data confirmed the putative close association between D. sonjae and D. lepontinus , the pairwise sequence distance of which exhibited 5.9–6.5 % difference in mitochondrial Cox 1 (p-distance; Suppl. material 1: table S 2), whilst all other species examined exhibited at least 11 % and more. Intraspecific variation was found to be up to 0.61 %.

Figures

Figures 1–17. Dichotrachelus sonjae and D. lepontinus. 1, 2. Male and female of D. sonjae; 3, 4. Male of D. sonjae aedeagus ventral and lateral view; 5, 6. Male and female of D. lepontinus; 7, 8. Ditto, aedeagus ventral and lateral view; 9. Ventral view of D. sonjae; 10. Ditto, D. lepontinus; 11–13. Internal sclerite of aedeagal sac of D. sonjae, dorsal, ventral and lateral view; 14, 15. A pair of spinal projections on the ventral base of left protibia, the duplex lobal spurs, dorsal and lateral view of D. sonjae; 16, 17. Ditto, D. lepontinus (Photos: C. Germann).

Figures 18–23. Female genital organs of D. sonjae. and D. lepontinus. 18, 20, 22 Female genitalia of Dichotrachelus sonjae. 18. Sternite VIII; 20. Spermatheca; 22. Gonocoxites. 19, 21, 23 Ditto of D. lepontinus (Photos: C. Germann).

Figures 24–27. 24, 25. Habitat of D. sonjae in the scree slope north of Pizzo Nona at nearly 2000 m a. s. l. (corresponds to the line ending with the rock face above). The extraordinary coldness of this place is due to the extra cavity carved into the north face of Pizzo Nona, that can be seen in Fig. 24 above the middle in the picture, thus the habitat is deprived from direct sunlight most of the year; 26, 27. Last and first larval stages of D. sonjae collected in moss cushions growing on granite stones in the scree slope (Photos: C. Germann).