Mecinus laeviceps Tournier, 1873

Gosik, Rafal, Skuhrovec, Jiri, Caldara, Roberto & Tosevski, Ivo, 2020, Immature stages of Palearctic Mecinus species (Coleoptera, Curculionidae, Curculioninae): morphological characters diagnostic at genus and species levels, ZooKeys 939, pp. 87-165 : 87

Mecinus laeviceps Tournier, 1873

Material examined.

8 L3 larvae and 10 pupae, Serbia, Slankamen, 22.06.2017 45°08.343'N, 20°15.042'E, 177 m., ex Linaria genistifolia , lgt. I. Toševski. Accession numbers of sequenced specimen MN992003.

Description of mature larva

(Figures 31A-D , 32A-F ). Measurements (in mm). Body length: 1.67-2.67. Body width (abdominal segments I-II): 0.37-0.83. Head width: 0.30-0.40.

Body (Figure 31A-D ) yellowish, slender. Chaetotaxy rather weakly developed, setae capilliform, variable in length, light yellow. Prothorax (Figure 31B ) with nine prns of unequal length (eight relatively long, one medium); two long ps and one medium eus. Meso- and metathorax (Figure 31B ) with one short prs, two pds, different in length (medium, long), one short as, three short ss, one medium eps, one medium ps and one medium eus. Pedal area with three pda, different in length. Abdominal segments I-VIII (Figure 31C, D ) with one short prs, three pds of different length (pds1,3 short, pds2 medium; all pds on segment VIII very long, equal in length), arranged along the posterior margin, two short ss, two short eps, one medium ps, one short lsts and two short eus. Abdominal segment IX (Figure 31D ) with two long ds, located close to posterior margin, one long ps and two short sts. Each lateral anal lobe with one minute seta.

Head capsule (Figures 31A , 32A-F ) light yellow, distinctly narrowed bilaterally. Des1-3,5 long, equal in length; des4 very short; des4 located in the central part of epicranium. Fs3 short to very short, fs4,5 long, equal in length. Les1 and les2 long, equal in length; two ves and one pes very short (Figure 32A ). Antenna (Figure 32B ) with sensorium (Se) conical, three times as long as wide, and three sensilla: one sa and two sb. Clypeus (Figure 32C ) trapezium-shaped, anterior margin slightly concave; cls2 medium; clss placed close to cls2. Labrum (Figure 32C ) almost semi-circular, anterior margin sinuated; lrs1 long, both lrs2 and lrs3 medium. Epipharynx (Figure 32D ) with three finger-like als of almost equal length; two finger-like ams, both medium; two short finger-like mes, surface smooth; labral rods short, kidney-shaped. Mandibles (Figure 32E ) conical, wide, with a small protuberance in the middle of the cutting edge; both mds capilliform, medium, equal in length, placed transversely. Maxilla (Figure 32F ) with one stps and two pfs of equal length; mbs short; mala with six rod-like dms different in length (dms1,2 medium, dms3-6 long to very long), five vms different in length. Maxillary palpi: basal palpomere wider than distal, both of almost equal length. Prelabium (Figure 32F ) oval-shaped with one long prms; ligula with two short ligs; premental sclerite clearly visible, U-shaped. Postlabium (Figure 32F ) with very short pms1, long pms2, and medium pms3.

Description of pupa

(Figure 33A-C ). Measurements (in mm). Head width: 0.35-0.40. Body width: 0.87-1.07. Body length: 2.12-2.50.

Body elongated, white. Rostrum slender, about four times as long as wide, reaching up to mesocoxae. Antennae slender and elongated. Pronotum 1.5 times as wide as long. Urogomphi (ur) very short, conical, with sclerotised apex, only slightly reaching outline of the body, directed downward (Figure 33B, C ).

Chaetotaxy sparse, setae short, unequal length. Head with one os. Rostrum with one rs and one pas. Setae on head and rostrum straight, as long as those on prothorax (Figure 33A ). Pronotum with one as, one ls, one ds and three pls. Dorsal parts of meso- and metathorax with three setae placed medially. Abdominal segments I-VIII with three very short setae ventrally, distributed in regular lines. Dorsal parts of abdominal segments I-VII with five setae (d1 placed anteromedially, d2-4 posteromedially, d5 posterolaterally); segment VIII with four setae dorsally. Abdominal segment IX with two micro-setae ventrally.

Biological notes.

This is a monophagous species associated with broomleaf toadflax, Linaria genistifolia (L.) Mill. The adults are active from early spring, following the appearance of the growing shoots of its host plant. The adults feed intensively on shoot points and apical leaves. Females oviposit batches of 3-6 eggs into the lower to middle part of the young growing shoots. Larval development usually induces stunted growth in the young shoot. The larvae develop in the central part of the stem, forming a relatively short tunnel and the formation of a pseudo-gall in which pupation takes place in the larval chamber very close to the stem surface. Like M. heydenii , the adults stay inside the stem until mid-August, when all adults leave their host plants. Adults overwinter in the soil close to the host plant.

Remarks and comparative notes.

There are three cryptic subspecies of this species that are distinguishable by molecular and biogeographical data ( Toševski et al. 2014). We studied the nominal subspecies distributed in the Czech Republic, Hungary, northern Serbia, and southern Russia; the subspecies meridionalis Toševski & Jović, 2014 is distributed in Serbia and Bulgaria and the subspecies corifoliae Toševski & Jović, 2014 is distributed in Turkey. As reported in the remarks on M. heydenii , several characters allow us to distinguish this last species and M. peterharrisi from M. laeviceps .

Figures

Figure 31. Mecinus laeviceps mature larva, habitus and chaetotaxy A habitus of the body and frontal view of the head B lateral view of thoracic segments C lateral view of abdominal segment I D lateral view of abdominal segments VII-X. Abbreviations: Th. I-III - number of thoracic segments, Abd. I-X - number of abominal segments, setae: as - alar, ds - dorsal, eps - epipleural, eus - eusternal, lsts - laterosternal, pda - pedal, pds - postdorsal, prns - pronotal, prs - prodorsal, ps - pleural, ss - spiracular, sts - sternal, ts - terminal.

Figure 32. Mecinus laeviceps mature larva, head and mouth parts A head, frontal view B antenna C clypeus and labrum, dorsal view D epipharynx E left mandible F maxillolabial complex, ventral aspect. Abbreviations: at - antenna, clss - clypeal sensorium, des - dorsal epicranial, lr - labral rods, sa - sensillum ampullaceum, sb - sensillum basiconicum, Se - sensorium, st - stemmata, setae: als - anterolateral, ams - anteromedial, cls - clypeal, dms - dorsal malar, fs - frontal, ligs - ligular, lrs - labral, ls - lateral epicranial, mbs - malar basiventral, mds - mandibular, mes - median, mxps - maxillary palp, pes - postepicranial, ves - ventral, pfs - palpiferal, pms - postlabial, prms - prelabial, stps - stipal, vms - ventral malar.

Figure 33. Mecinus laeviceps pupa habitus and chaetotaxy A ventral view B lateral view C dorsal view. Abbreviations: Th. I-III - number of thoracic segments, Abd. I-IX - number of abdominal segments, ur - urogomphi, setae: as - apical, d - dorsal, ds - discal, fes - femoral, l, ls - lateral, os - orbital, sls - postantennal, pls - posterolateral, rs - rostral.