Mecinus janthinus Germar, 1821

Caldara, Roberto & Fogato, Valter, 2013, Systematics of the weevil genus <i> Mecinus </ i> Germar, 1821 (Coleoptera: Curculionidae). I. Taxonomic treatment of the species, Zootaxa 3654 (1), pp. 1-105 : 67-69

38. Mecinus janthinus Germar

Figs 36 , 90–91 , 140 , 153 , 169

Mecinus janthinus Germar, 1821: 319 ; 1822: 10 (as ianthinus). Rosenschoeld, 1938: 779. Tournier, 1874: 41. Bedel, 1885: 148; 1887: 312; 1888: 426; 1923: 72. Desbrochers des Loges, 1893: 59. Reitter, 1907: 8; 1916: 225. Hustache, 1931: 400. 404. Hoffmann, 1958: 1267, 1269. Angelov, 1971: 117, 118. Smreczyṅski, 1976: 24. Lohse & Tischler, 1983: 261. Toševski et al., 2011: 748.

Mecinus violaceus Dejean, 1821: 98 ; 1836: 327 (nomen nudum).

Mecinus pillichi Endrǒdi, 1969: 276 . Smreczyṅski, 1976: 4. Toševski et al., 2011: 749.

Type locality. Odenbach (Rhineland-Palatinate, Germany).

Type series. Mecinus janthinus was described based on specimens from Odenbach ( Germany). In Germar’s collection at MLUH under the name janthinus Toševski et al. (2011) found two syntypes without labels, one male and one female which they designated as lectotype and paralectotype respectively.

Synonyms. The name violaceus , always placed among the synonyms of M. janthinus , is quoted by Dejean (1821; 1836) without a description. Therefore it must be considered a nomen nudum and is not available according to Art. 12 of ICZN (1999).

Mecinus pillichi was described from a single male specimen from Simontornya ( Hungary), which is deposited at HNHM. Endrôdi (1969) reported that this specimen differs from other blue coloured species of Mecinus by the elytral striae formed by very broad punctures. Toševski et al. (2011) agree with Smreczyṅski (1976) who synonymized this taxon with M. janthinus .

Redescription. Male. Length mm 3,1. Body: long, cylindrical, moderately slender ( Fig. 36 ). Rostrum: black, moderately long (Rl/Pl 0.84), subcylindrical; in lateral view moderately curved, almost of same width from base to apex ( Fig. 90 ); in dorsal view with parallel sides, slightly narrowed at base and in front of antennal insertion, with moderately visible scrobe, moderately striate-punctured to near apex, with deeper sulcus along midline and with wider and smoother intervals at sides of this sulcus, in basal half with recumbent, sparse, white, long (l/w 4–8), seta-like scales. Head: frons slightly narrower than rostrum at base, with shallow wide fovea; eyes nearly flat. Antennae: black, inserted just behind middle of rostrum; scape long, 7.0x longer than wide; funicle about as long as scape, segment 1 3.0x longer than wide, about as stout as and twice as long as segment 2, which is 1.7x longer than wide, segment 3 about as long as wide, segments 4 and 5 transverse; club long, oval, segment 1 about as pubescent as others. Pronotum: black with bronze and blue reflexions, with dense and regular punctures, intervals between punctures smooth and shining, clearly visible between recumbent, sparse, whitish, long (l/w 5–8), setalike scales; weakly transverse (Pw/Pl 1.13), with weakly rounded sides, with apical constriction moderately prominent, widest in basal third, somewhat convex. Elytra: black with distinct blue reflexions; very long (El/Ew 2.00), at base moderately concave, with parallel sides, slightly wider than pronotum (Ew/Pw 1.14), somewhat convex on disc; interstriae clearly visible between recumbent, sparse, white, 0.5–0.75x as long as width of interstria (l/w 5–8), seta-like scales, arranged in 1–2 regular rows; striae clearly visible, one third narrower than interstriae, with a row of scales similar in length to the shorter one covering interstriae. Legs: moderately slender, with recumbent to subrecumbent, sparse, whitish, seta-like scales, distinctly shorter than width of tibia; femora black, profemora with disticnt sharp tooth, mesofemora with small tooth, metafemora unarmed; tibiae black, moderately slender; protibiae with apical part of ventral surface weakly directed outward; unci blackish, stout, all equal in shape and length; tarsi blackish brown, long, tarsomere 1 3x longer than wide, tarsomere 2 2x longer than wide, segment 3 distinctly bilobed and distinctly wider than tarsomere 2, onychium shorter than tarsomeres 1–3 taken together; claws blackish, equal in length, fused in basal half. Venter: metasternum black, clearly visible between recumbent, sparse, whitish, moderately long, seta-like scales; mesothoracic epimera and meso- and metathoracic episterna with sparse, white, moderately long, hair-like scales, and rare fringed wide scales; abdomen black, with dense and somewhat regular punctures, which are clearly visible between recumbent, sparse, whitish, long, hairlike scales; ventrites length ratio: 1–2/3–4 1.96. Penis: fig. 140.

Female. As in male except rostrum somewhat longer (Rl/Pl 1.02) ( Fig. 91 ), less punctured, antennae inserted just in front of middle of rostrum, femora unarmed, metatibiae without uncus. Sternite 8: fig. 153. Spermatheca: fig. 169.

Variability. Length 2.4–3.4 mm. Rl/Pl male 0.75– 0.86; female 0.95–1.04. Sometimes the frons lacks the fovea. The elytral scales vary distinctly in length (also a quarter as long as width of the interstria). Sometimes the elytra are weakly enlarged at their apical third.

Remarks and comparative notes. Mecinus janthinus can be confused with M. janthiniformis and M. kaemmereri (see Remarks and comparative notes of these two species). On the contrary it is easy to distinguish these three species from the others with blue elytra by the less abruptly curved rostrum and by the shape of the penis.

Biological notes. The biology of this species was very carefully studied by Toševski et al. (2011). The host plant of M. janthinus is L. vulgaris Miller. The adults emerge from the dry stems in early March and feed intensively on the newly growing shoots of the host plant. Copulation occurs shortly after and the egg-laying period lasts from the end of March until mid-June. Oviposition occurs on actively growing shoots and the preferred oviposition site is always the widest part of the stem, usually within the lower stem. Before oviposition, the female prepares a shallow hole in which the egg is deposited. During oviposition, the female secretes a sticky fluid that fixes the egg to the plant tissue. Females lay one, rarely two, eggs per shoot. Mecinus janthinus is a true stem borer with larvae feeding and mining in the central part of the stem. Mine length typically varies from 1 to 2 cm, but can be up to 10 cm long if the stem tissue is stressed by a low water regime. Under these conditions, larvae move to the upper or lower stem where tissue conditions provide a better source of nutrition. In southeast Europe, adults of M. janthinus can occasionally be collected in early spring on L. genistifolia (L.) Miller, L. rubioides ssp. nissana Petrovic and L. angustissima (Loisel.) Re at stands where these plants are sympatric with L. vulgaris , but larval development has never been recorded on these plant species (Toševski et al. 2011). The dominant parasitoid of M. janthinus in southeast Europe is Entedon sparetus Walker, 1839 ( Hymenoptera , Eulophidae , Entedoninae ), which parasites over 50% of larvae.

Distribution. Northern ( Sweden, Baltic States), central and southeastern Europe ( Great Britain, France, Belgium, the Netherlands, Poland, Germany, Switzerland, Italy, Czech Republic, Slovakia, Hungary, Austria, Serbia, Ukraine, Moldova Republic, Romania, Bulgaria, Greece), Russia from the western borders (north to south) to southern central Siberia, the Caucasian states, Turkey. This species has been introduced in North America for biological control of toadflaxes in 1991–1999 ( Wilson et al. 2005).

Non-type specimens examined. About 600 specimens from Sweden, Russia, France, Germany, Switzerland, Italy, Czech Republic, Slovakia, Hungary, Serbia, Romania, Bulgaria, Greece, Turkey.

Figures

FIGURES 28–36. Habitus of (28) Mecinus baridioides; (29) M. comosus; (30) M. simus; (31) M. pirazzolii; (32) M. vulpes; (33) M. pipistrellus; (34) M. collaris; (35) M. sicardi; (36) M. janthinus. Not to the same scale.

FIGURES 88–97. Rostrum in lateral view of (88) Mecinus kaemmereri, female; (89) M. setulosus, male; (90) M. janthinus, male; (91) idem, female; (92) M. barbarus, male; (93) idem, female; (94) M. dorsalis, male; (95) idem, female; (96) M. tavaresi, male; (97) idem, female. Scale bar = 0.5 mm.

FIGURES 133–143. Penis in dorsal and lateral view of (133) Mecinus vulpes; (134) M. pipistrellus; (135) M. collaris; (136) M. lixoides; (137) M. sicardi; (138) M. janthiniformis; (139) M. barbarus; (140) M. janthinus; (141) M. heydenii; (143) M. tavaresi; (142) M. aubei. Scale bar = 0.2 mm.

FIGURES 144–156. Sternite 8 of (144) Mecinus pascuorum; (145) M. caucasicus; (146) M. marina; (147) M. reichei; (148) M. humeralis; (149) M. circulatus; (150) M. pyraster; (151) M. simus; (152) M. collaris; (153) M. janthinus; (154) M. lixoides; (155) M. sicardi; (156) M. heydenii. Scale bar = 0.2 mm.

FIGURES 157–171. Spermatheca of (157) Mecinus pascuorum; (158) M. caucasicus; (159) M. haemorrhoidalis; (160) M. labilis; (161) M. marina; (162) M. elongatus; (163) M. reichei; (164) M. circulatus; (165) M. pyraster; (166) M. simus; (167) M. comosus; (168) M. lixoides; (169) M. janthinus; (170) M. heydenii; (171) M. collaris. Scale bar = 0.2 mm.