Gymnetron melanarium (Germar, 1821)

Skuhrovec, Jiri, Gosik, Rafal, Caldara, Roberto, Tosevski, Ivo & Batyra, Aleksandra, 2022, Description of immature stages of Gymnetron species (Coleoptera, Curculionidae, Curculioninae), with particular emphasis on the diagnostic morphological characters at the generic and specific levels, ZooKeys 1090, pp. 45-84 : 45

publication ID	https://dx.doi.org/10.3897/zookeys.1090.78741
publication LSID	lsid:zoobank.org:pub:DA810EFD-D63C-49C4-B1CA-D346B3C00C37
persistent identifier	https://treatment.plazi.org/id/39922FEF-B664-5F58-971A-13E99C4031CF
treatment provided by	ZooKeys by Pensoft
scientific name	Gymnetron melanarium (Germar, 1821)
status

Treatment

Material examined.

Serbia, Pirot, Ponor , GPS 43°11.013'N, 22°25.067'E, 686 m, ex Veronica austriaca subsp. jacquinii , 20.06.2020, leg. Toševski (35 larvae and 11 pupae) GoogleMaps .

Description of mature larva

(Figs 16A, B View Figure 16 , 17A-F View Figure 17 , 18A, B View Figure 18 ). Measurements (in mm). Body length: 2.33-2.66. The widest point in the body (meso- and metathorax) measures up to 1.00. Head width: 0.50-0.53.

General. Body elongate, slender, weakly curved, rounded in cross section (Fig. 16A View Figure 16 ).

Colouration. Head pale yellow (Fig. 16B View Figure 16 ). All thoracic and abdominal segments smooth (Fig. 16A View Figure 16 ).

Vestiture. Setae on body thin, yellow, distinctly different in length (minute to very short or long).

Head capsule (Figs 16B View Figure 16 , 17A View Figure 17 ). Head almost oval, endocarinal line present, extending distinctly to 3/4 of the length of frons. Frontal sutures on head distinct. Stemma, in form of pigmented spot with convex cornea. Des1 medium, located in middle of central part of epicranium; medium des2; medium des3 located anteriorly on epicranium, close to border with frontal suture; medium des4; medium des5 placed laterally (Fig. 17A View Figure 17 ). Fs1 absent; fs2 medium, located medially; fs3 absent; fs4 medium, located anteriorly; and fs5 long, located anterolaterally, close to antenna (Fig. 17A View Figure 17 ). Les1 medium and les2 as long as des5; single ves medium. Epicranial area with six postepicranial setae.

Antennae membranous and distinctly convex basal membranous article bearing one relatively long conical sensorium and four sensilla: three basiconica and single ampullaceum (Fig. 17B View Figure 17 ).

Clypeus (Fig. 17C View Figure 17 ) ~ 3 × as wide as long with two relatively long cls, located posterolaterally, with single sensillum; fused to labrum.

Mouth parts. Labrum (Fig. 17C View Figure 17 ) ~ 3 × as wide as long, with three piliform lms, relatively long, lms3 slightly shorter than others; lms1 located anteromedially, lms2 located partly close to clypeus, and lms3 located anterolaterally. Epipharynx (Fig. 17D View Figure 17 ) with three very long digitate als, almost identical in length; with two piliform ams, equal in length, and one short, digitate mes; labral rods indistinct, narrow. Mandibles (Fig. 17E View Figure 17 ) with two relatively long, piliform mds, located in distinct holes. Maxilla (Fig. 17F View Figure 17 ): stipes with one stps, two pfs and one sensillum, without mbs; stps and both pfs long; mala with five moderately elongate digitate dms; four vms, different in length, two setae short, and two setae very short. Maxillary palpi with two palpomeres; length ratio of basal and distal palpomeres: 1:1.2. Praelabium (Fig. 17F View Figure 17 ) oval, with one medium prms; ligula with rounded margin and two very short ligs; premental sclerite broad, well visible. Postlabium (Fig. 17F View Figure 17 ) with three pms, short pms1, very long pms2 and short pms3, all located laterally; membranous area densely and distinctly asperate.

Thorax. Prothorax (Fig. 18A View Figure 18 ) with nine long and one minute prns; two long ps; and two very short eus. Mesothorax (Fig. 18A View Figure 18 ) with two minute prs; one medium and two long pds; one long as; two long and one minute ss; one long eps; one long ps; and one short eus. Chaetotaxy of metathorax (Fig. 18A View Figure 18 ) almost identical to that of mesothorax. Each pedal area of thoracic segments well separated, with one long, two medium and two very short to minute pda.

Abdomen. Spiracles on abdominal segments I-VI placed medially and functional, spiracles on abdominal segment VII not functional, and abdominal segment VIII with atrophied spiracles. Abdominal segments I-VI (Fig. 18B, C View Figure 18 ) with one minute prs; one long and one medium pds; one long and one very short to minute ss; one long eps; one relatively long ps; without lsts and two very short eus. Abdominal segments VII-VIII (Fig. 18C View Figure 18 ) without prs; one long and one medium pds; one very short to minute ss; one long eps; one long ps; and two very short eus. Abdominal segment IX (Fig. 18C View Figure 18 ) with one relatively long ds; one relatively long ps; and one medium sts. Abdominal segment X (Fig. 18C View Figure 18 ) with one very short seta (ts).

Description of pupa

(Figs 19A-C View Figure 19 , 20A-C View Figure 20 ). Measurements (in mm). Body length: 2.12-2.32. Body width: 1.25-1.32. Thorax width: 0.75-0.82.

Body. Yellowish, pronotal protuberances (p-pr) sclerotized, smooth; head, rostrum, antennae, dorsal parts of meso- and metanotum, and apical parts of femora brownish. Rostrum rather slender. Pronotal protuberances well separated. Pronotum 1.8 × as wide as long. Mesonotum slightly smaller than metanotum. Urogomphi reduced, conical, with sclerotized apex. Abdominal segment VIII with conical abdominal protuberance dorsally (a-pr) having acute, sclerotized apex (Fig. 19A-C View Figure 19 ).

Chaetotaxy. Sparse, setae rather short to moderately elongate, transparent. Head with two os, different in length. Rostrum with one rs. Setae on head and rostrum straight, as long as those on prothorax (Fig. 20B View Figure 20 ). Pronotum with two as, two ls, two ds and four pls; ds1 - 2 and ls2 slightly shorter than other pronotal setae. Dorsal parts of meso- and metathorax with two setae placed medially. Apex of femora with two fes equal in length (Fig. 20A-C View Figure 20 ). Abdominal segments I-VIII with five short, equally long setae dorsally: first placed antero-medially, the others distributed in regular line along posterior margin of segment. All dorsal abdominal setae short, almost equal in length. Each lateral part of abdominal segments I-VIII with one elongated seta. Ventral parts of abdominal segments I-VIII with three medium setae. Abdominal segment IX with two very short setae ventrally (Fig. 20A-C View Figure 20 ).

Biological notes.

Previously the larva of this species was observed on Veronica serpyllifolia L., on the stems where it produces a small uni- or bilocular gall in which metamorphosis takes place. The adult emerges from the gall at the end of summer and hibernates in the soil ( Hustache 1931; Hoffmann 1958). The adult has also been collected on other Veronica species such as V. agrestis L., V. austriaca subsp. austriaca L., V. chamaedrys L., V. officinalis L, and V. teucrium (L.) D.A. Webb ( Hoffmann 1958; Koch 1992; Sprick 1997). In Serbia, the development of G. melanarium is restricted to the seed capsules of Veronica austriaca subsp. jacquinii (Baumg.) Watzl, which is new information. Nearly 90% of the seed capsules are infested with one or two larvae. The larvae are seed feeders and development occurs in the basal part of the strongly flattened, glossy and glabrous seed capsules with no visible sign of larval presence. Oviposition takes place from mid-May onwards and the new generation of adults emerges during July.

Remarks and comparative notes.

This species belongs to a group of very similar species characterized by slender subrectangular elytra, rostrum in lateral view tapered from the antennal insertion to the apex, and short protibiae in the female. There are no particular phylogenetic affinities with the adult (see Caldara 2008a) and pupal stages (abdominal protuberance short, triangular, head with 2 os) of the other species described here. By contrast, the larvae share several characters with G. rotundicolle , e.g., the praedorsal segment on abdominal segments with one pds, the epicranium lacking fs3, and the conical layout of the labral setae.