Immature stages of Palearctic Mecinus species (Coleoptera, Curculionidae, Curculioninae): morphological characters diagnostic at genus and species levels Author Gosik, Rafal Department of Zoology and Nature Protection, Maria Curie-Sklodowska University, Akademicka 19, 20 - 033 Lublin, Poland Author Skuhrovec, Jiri Group Function of Invertebrate and Plant Biodiversity in Agro-Ecosystems, Crop Research Institute, Prague 6 - Ruzyne, Czech Republic https://orcid.org/0000-0002-7691-5990 jirislavskuhrovec@gmail.com Author Caldara, Roberto Center of Alpine Entomology, University of Milan, Via Celoria 2, 20133 Milan, Italy Author Tosevski, Ivo CABI, Rue des Grillons 1, 2800 Delemont, Switzerland & Institute for Plant Protection and Environment, Banatska 33, 11080, Zemun, Serbia text ZooKeys 2020 939 87 165 http://dx.doi.org/10.3897/zookeys.939.50612 journal article http://dx.doi.org/10.3897/zookeys.939.50612 1313-2970-939-87 B239701148884712880E1069C943AD33 DB6D50A55057576896F6AFDAE5BC9922 Mecinus janthiniformis Tosevski & Caldara, 2011 Material examined. 2 L3 larvae, Mecedonia, Prilep, 25.07.2017, ( 41°17.354'N , 21°29.983'E , 618 m.) ex Linaria dalmatica macedonica 1 L3 larva, 4 pupae, Bulgaria, Harmanli, 17.08.2008, 41°53.117'N , 25°52.373'E , 310 m., ex Linaria genistifolia 12 L3 larva, Bulgaria, Harmanli, 17.07.2011, 41°53.117'N , 25°52.373'E , 310 m., ex L. genistifolia ; 2 L3 larvae, 1 pupa, Bulgaria, Slatino, 7.08.2011, 42°09.981'N , 23°02.371'E , 390 m., ex L. genistifolia ; 1 pupa, Serbia, Kalna, 1.09.2010., 43°29.450'N , 22°19.712'E , 278 m., ex L. genistifolia ; 3 pupae, Serbia, Bovansko Jezero, Aleksinac, 12.08.2010, 43°37.735'N , 21°42.917'E , 231 m., ex L. genistifolia ; North Macedonia, Veles, 10.09.2009, 41°44.332'N , 21°46.893'E , 201 m., ex L. genistifolia ; 1 pupa, Serbia, Vranje, Golemo Selo, 20.08.2009, 42°44.203'N , 21°50.696'E , 523 m., ex L. genistifolia ; 3 pupae, Bulgaria, Slatino, 7.08.2007, 42°09.981'N , 23°02.371'E , 390 m., ex L. genistifolia . All collected by I. Tosevski . Accession numbers of sequenced specimen MN992006. Description of mature larva (Figures 22A-D , 23A-F ). Measurements (in mm). Body length: 1.66-2.90. Body width (abdominal segments I-II): 0.66-1.10. Head width: 0.53-0.67. Body (Figure 22A-D ) yellowish. Prothorax smaller than meso- and metathorax. Abdominal segments I-VII of almost equal length; segments VIII and IX decreasing gradually to the terminal body part; segment X reduced to three anal lobes of those lateral are the largest, and dorsal the smallest (sometimes absent). Dorsum of abdominal segments I-VI divided into three lobes; on seventh into two lobes. Chaetotaxy well developed, setae various in length. Prothorax (Figure 22B ) with eleven long prns ; two medium ps and one medium eus. Meso- and metathorax (Figure 22B ) with one short prs , three pds ( pds1 short, pds2-3 medium), one medium as , three medium ss , one medium eps , one medium ps and one medium eus. Pedal area with six pda of different length (four of them placed on well isolated pedal sclerite). Abdominal segments I-VIII (Figure 22C, D ) with one short prs , four pds (on segments I-V: pds1,3 medium, pds2,4 short; on segments VI-VIII all pds very long, equal in length), always arranged along the posterior margin, one minute and two long ss , one short and one medium e ps , one medium ps , one medium lsts and two medium eus. Abdominal segment IX (Figure 22D ) with four long ds located close to posterior margin, two ps different in length, and two short sts. Each of anal lobe (abd. segment X) with two minute setae. Figure 22. Mecinus janthiniformis 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. Head capsule (Figures 22A , 23A-F ) dark yellow, narrowed bilaterally. Des1-3,5 very long, equal in length, des4 twice shorter than other des ; des4 medially. Fs1 as long as des1, fs3 short, fs4,5 long. Les1 and les2 equal in length, slightly shorter than des1 ; two ves and three pes very short (Figure 23A ). Two stemmata of different size. Antennae (Figure 23B ) with sensorium (Se) conical, twice as long as wide, and four sensilla basiconica (sb). Clypeus (Figure 23C ) trapezium-shaped, anterior margin concave; two medium cls , clss clearly visible. Labrum (Figure 23C ) with sinuate anterior margin; lrs1 long, lrs2 and lrs3 medium. Epipharynx (Figure 23D ) with three relatively long, finger-shaped als of almost equal length; two finger-shaped ams , equal in length; two rod-like mes of medium length; surface smooth; labral rods short, kidney shaped. Mandibles (Figure 23E ) conical, wide, with a small protuberance in the middle of the cutting edge; both mds capilliform, relatively short, equal in length, placed mediolaterally. Maxilla (Figure 23F ) with one stps and two pfs of equal length; mbs very short; mala with seven long finger-like dms of almost equal size, five vms different in length. Maxillary palpi: basal palpomere wider than distal, both of almost equal length. Prelabium (Figure 23F ) cup-shaped with one very long prms ; ligula with two relatively long ligs ; premental sclerite clearly visible, cup-like. Labial palpi two-segmented; basal palpomere distinctly wider than distal, both almost equal in length. Postlabium (Figure 23F ) with three medium pms . Figure 23. Mecinus janthiniformis 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, 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. Description of pupa (Figure 24A-C ). Measurements (in mm). Head width: 0.46-0.66. Body width: 1.20-1.66. Body length: 3.22-4.16. Body elongated, white. Rostrum slender, about four times as long as wide, reaching almost up to mesocoxae. Antennae slender and elongated. Pronotum 1.3 times as wide as long. Urogomphi (ur) slender and elongated, conical, with sclerotised apex, distinctly reaching outline of the body, directed outside (Figure 24A, C ). Chaetotaxy well developed, setae medium long or elongated, unequal length. Head with one long vs , two sos different in length, two os different in length and two sls different in length. Rostrum with one rs (Figure 24A ). Pronotum with two as , one ds , two sls , two ls , and three pls (Figure 24B, C ). All setae on prothorax elongated, equal in length (Figure 24C ). Setae on head and rostrum shorter than those on prothorax. Dorsal parts of meso- and metathorax with three setae placed medially. Abdominal segments I-VIII with two setae placed laterally and three medium long setae ventrally. Dorsal parts of abdominal segments I-VII with six setae ( d1-4 placed posteromedially, d5-6 posterolaterally); segment VIII with five very long setae dorsally. Abdominal segment IX with two micro-setae ventrally. Figure 24. Mecinus janthiniformis 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, sls - superlateral, sos - superorbital, vs - vertical. Biological notes. The host plants of M. janthiniformis are Linaria genistifolia (L.) Mill. and L. dalmatica (L.) Mill., as well as all variable forms and hypothetical hybrids between these two plant species. Mecinus janthiniformis inhabits stands from lowlands to mountain pastures and meadows up to 1500 m. At the beginning of the 1990s, this species was introduced as a biological control agent for the control of invasive toadflaxes in North America ( Tosevski et al. 2018 ). Adults emerge in early spring and feed on the apical part of newly growing shoots. The females lay eggs over the next three months on the upper part of the main stem, including the lateral branches of the plant. Oviposition and larval development induce a slightly elongate gall in which the larvae pupate. The adults of this species overwinter inside the main stem of the host plant or inside induced galls on lateral branches ( Tosevski et al. 2011 ). Remarks and comparative notes. The distribution of M. janthiniformis follows that of the two host plants, L. genistifolia (L.) Mill. and L. dalmatica (eastern part of central and southeastern Europe to southern central Siberia, the northern Caucasian states and Turkey). Its separation from M. janthinus at the species level was clearly shown based on very careful biological and genetic studies ( Tosevski et al. 2011 ), but unfortunately, easy identification is only possible by collecting the specimens together with their host plants. Usually, in M. janthiniformis , the body is larger (length 3.2-6.0 mm), the apical part of the rostrum in females in lateral view is more curved, the punctures of the pronotum are slightly smaller and more densely adpressed, and the scales of the elytral interstriae are denser, arranged in two rows on part of several interstriae. The larvae of these two species show numerous differences in the number of setae in many parts of the body, whereas the differences are few in the pupae (see keys).