Rhinusa linariae

Rhinusa linariae (Panzer, 1795)

Figs 1, 10, 11, 24, 27, 33, 39

Curculio linariae Panzer, 1795: 18. Caldara 2008: 126 (nomen protectum).

Cionus linariae (Panzer). Germar 1821: 314.

Miarus linariae (Panzer). Stephens 1831: 16.

Gymnetron linariae (Panzer). Rosenschoeld 1838: 769. H. Brisout de Barneville 1863: 651. Desbrochers des Loges 1893: 35. Reitter 1907: 43; 1916: 231. Hustache 1932: 412, 429. Hoffmann 1958: 1281, 1311. Smreczyński 1976: 35. Lohse & Tischler 1983: 267.

Mecinus linariae (Panzer). Bedel 1885: 146; 1887: 307. Sainte-Claire Deville 1924: 69.

Rhinusa linariae (Panzer). Caldara 2001: 185; 2008: 126. Caldara et al. 2010: 52. Alonso-Zarazaga et al. 2017: 203.

Curculio curvirostris Rossi, 1790: 117. Hellwig 1795: 125. H. Brisout de Barneville 1863: 652. Caldara 2008: 126 (nomen oblitum).

Type locality. Eberswalde (Brandeburg, Germany). Type series. The neotype was designated by Caldara (2008).

Synonyms. Curculio curvirostris was described by Rossi (1790) from specimens collected in Tuscany (Italy). The neotype of this species (type locality: Italy, Lazio, Roma, Formello) was recently designated and its synonymy with R. linariae discussed by Caldara (2008). The junior name linariae can be maintained, since Curculio curvirostris Rossi is a junior homonym of Curculio curvirostris Fabricius, 1781, an Indonesian baridine, and also of Curculio curvirostris Herbst, 1784, a probable synonym of Exapion fuscirostre fuscirostre (Fabricius, 1775) (Alonso- Zarazaga et al. 2017).

Redescription. Male. Body: oval, stout (Fig. 1). Rostrum: black, short (Rl/Pl 0.75); in lateral view strongly curved, very stout in basal third, further slightly narrowed to apex (Fig. 10); in dorsal view with subparallel sides, with moderately visible scrobes, striate-punctate in basal two thirds, smoother and shining along midline and in apical third, with sparse recumbent short (l/w 2–3) whitish scales in basal third. Head: between eyes as wide as rostrum at base, without fovea. Eyes almost flat. Antennae: dark brown, inserted at middle of rostrum; scape 2.5× longer than wide, funicle distinctly longer than scape, with segment 1 twice longer than wide, slightly stouter than and about as long as segment 2, which is 2.5× longer than wide, segments 3–5 gradually becoming more transverse; club oval, with segment 1 pubescent similarly to others. Pronotum: black, densely and rather regularly punctate, intervals between punctures narrow, smooth and shining, well visible between sparse recumbent moderately long (l/ w 4–6) subelliptical whitish scales; transverse (Pw/Pl 1.35), with distinctly rounded sides, widest between basal and middle thirds, distinctly constricted at apex, almost flat. Elytra: black, 1.28× as long as wide, subelliptical, 1.32× as wide as pronotum, with basal margin transverse until interstria 5, further beveled anteriorly, with moderately rounded sides, widest at middle, weakly convex on disc; interstriae well visible between sparse recumbent, elliptical to sublanceolate whitish scales, 0.50–0.75× as long as width of interstria (l/w 4–7) and arranged in 2–3 irregular rows; striae well visible, half as wide as interstriae, with a row of scales slightly narrower than those on interstriae. Legs: stout, with sparse recumbent to suberect whitish scales distinctly shorter than width of tibia; femora black, subclavate, without tooth; tibiae black, stout, distinctly sinuous at middle, with outer margin moderately carinate; unci black, thin, all of same size; tarsi brown, with tarsomere 1 1.7× longer than wide, tarsomere 2 1.2× longer than wide, tarsomere 3 bilobed and distinctly wider than tarsomere 2, onychium as long as tarsomeres 1–3 taken together; claws dark brown, equal in length. Venter: metasternum black, with sparse subrecumbent long setiform whitish scales. Mesepimera, mes- and metepisterna with sparse long setiform whitish scales. Abdomen black, with dense and somewhat regular punctures, well visible between sparse recumbent to subrecumbent setiform whitish scales; length ventrites 1+2/3+4 1.95 Penis (Fig. 27): body of penis very long (l/ w 6.0), nearly parallel-sided, with broad apex; apodemes distinctly shorter than body, in lateral view forming an angle of 60 degrees in relation to body.

Female. Rostrum slightly longer (Rl/Pl 0.81) (Fig. 11), in dorsal view smooth and shining from antennal insertion to apex, antennae inserted between basal and middle thirds of rostrum. Spiculum ventrale: arms moderately spaced each other, apodeme slightly longer than arms (Fig. 33). Spermatheca: ramus very short, collum well-developed (Fig. 39).

Variability. Length 2.6–3.1 mm. Pronotum and elytra vary slightly both in curvature of sides and convexity. The rostrum varies a little in length in both sexes (Rl/Pl male 0.72–0.78; female 0.78–0.85).

Remarks and comparative notes. The three species of this group are very similar to each other and have very similar shape of the genitalia. Rhinusa linariae differs from the other two species by the completely black integument. In addition, it differs from R. brisouti by the less broad pronotum, the more elongate elytra and the protibiae being less distinctly carinate and with the outer margin less directed outward apically, and from R. kumatschevi by the protibiae being more deeply sinuate in the middle.

Biological notes. Rhinusa linariae is a univoltine root galling weevil. Gall induction and larval development are mainly recorded on Linaria vulgaris Mill. and rarely on L. genistifolia (L.) P. Mill. in Southeastern Europe. Adults emerge in early spring, feed and copulate on the top of the young toadflax shoots. Females lay eggs singly or in small groups on toadflax roots or below root crowns. Shortly after, oviposition triggers gall formation, and larvae feed on galled root tissue through three instars. Pupation occurs in galls, while new adults emerge in mid- to late summer or rarely stay inside galls during winter, overwintering in soil or in plant litter close to their host plant.

Twenty-five years ago, Rhinusa linariae was introduced as a biological control agent for invasive toadflaxes in Canada and USA, where it was recently confirmed as established only in British Columbia; however, the current populations are still too low to have a significant biological impact (Sing et al. 2015).

Distribution. This species is widely distributed in the whole Europe, Turkey, Kazakhstan and Western Siberia. Introduced in North America.

Non-type material examined. France: Paris (3, BMNH). Italy: Piemonte, Asti, Nizza Monferrato, Frazione Barca, 28.VII.1978, leg. Diotti (1, LDCC); Lombardia, Monza Parco, IV.1948, leg. Loro (1, MSNM); Lombardia, Lecco, Monte Barro, 15.VI.1990, leg. Leonardi (14, MSNM); Veneto, Verona, Fumane, 17.V.1981, leg. Osella (1, GOCV); Veneto, Vicenza, Alta Val d'Astico, 21.VI.1997, leg. Diotti (1, LDCC); Veneto, Vicenza, Monti Berici, Lago di Fimon, 26.IV.2010, leg. Diotti (1, LDCC); Veneto, Vicenza, Monti Berici, Soghe, 19.IV.2011, leg. Diotti (1, LDCC); Friuli-Venezia Giulia, Gorizia, Grado, Belvedere, 12.VI.1912, leg. Springer (1, MSNM); Friuli-Venezia Giulia, Trieste, Prosecco, 10.V.1925, leg. Springer (1, MSNM); Friuli-Venezia Giulia, Trieste, Zaule, 10.V.1923, leg. Springer (1, MSNM); Liguria, Genova, Madonna della Guardia, 4.VII.2002, leg. Diotti (1, LDCC); Liguria, Genova, Gattorna, 1–10.VII.1979, leg. Caldara (3, RCCM); Liguria, La Spezia, 6.VI.1971, leg. Caldara (1, RCCM); Liguria, La Spezia, Castelnuovo Magra, 12.V.1980, leg. Caldara (1, RCCM); Liguria, Savona, Celle Ligure, 10.V.1969, leg. Ragozzino (1, RCCM); Emilia Romagna, Piacenza, Bettola, 28.V.1970, leg. Caldara (1, RCCM); Toscana, Firenze, V.1942, leg. Lombardi (2, MSNM); Toscana, Firenze, Palazzuolo, 14.V.2000, leg. Mingazzini (1, LDCC); Toscana, Livorno, Piombino, 8.V.1971, leg. Caldara (1, RCCM); Lazio, Roma, Palestrina, Frazione Carchitti, 20.V.1973 (1, RCCM); Lazio, Roma, Rocca di Papa, Monte Cavo, 900 m, 30.V.2005, leg. Colonnelli (1, ECCR); Abruzzo, L'Aquila, Raiano, 10.V.2002, leg. Osella (1, GOCV); Abruzzo, Pescara, Popoli, 19.V.1996, leg. Osella (2, GOCV); Abruzzo, Pescara, Popoli, Sorgenti fiume Pescara, 11.V.2002, leg. Osella (3, GOCV); Abruzzo, Teramo, Campo Battaglia, 5.V.2002, leg. Osella (2, GOCV); Italy (Sicily): Messina, Monti Nebrodi, Alcara Li Fusi, 27.IV.2016, leg. Casalini (RCCR); Messina, Monte Etna, Piano Provenzana, 1800-2200 m, on Linaria purpurea, 22.VI.2012, leg. Baviera (CBCM). Germany: Baden-Württemberg, Leimen near Heidelberg, 400 m, 27.V.1990, leg. Košťál (1, MKCH). Hungary: Mecsek Mts., Hosszúhetény Zengö Hill, 400 m, 25.IV.1987, leg. Košťál (1, MKCH). Slovenia: Istria, Podgorje, 28.X.1937, leg. Springer (1, MSNM); Nanos Mount, 750 m, 18.V.1994, leg. Košťál (1, MKCH). Romania: Báziás, leg. Zoppa (1, MSNM); Cîmpia Crişurilor, Rovine near Arad, 21.IV.1983, leg. Košťál (1, MKCH). Turkey: Kirşehir, 4 km S of Mucur, 10.V.1997, leg. Sama (1, FTCM). Russia: Volgogradskaya Oblast’, 8 km E of Perekopskij, VI.2005, leg. Tronci (1, ECCR). Kazakhstan: Aktjubinsk, Karaholda River, Novoalekseevka, 26.V.2000 (1, RCCM).