Gymnetron villosulum Gyllenhal, 1838

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/ADB0D1D2-2375-5249-A786-687F3865040A
treatment provided by	ZooKeys by Pensoft
scientific name	Gymnetron villosulum Gyllenhal, 1838
status

Treatment

Gymnetron villosulum Gyllenhal, 1838 View in CoL

Material examined.

Serbia, Boljetin , GPS 44°30.973'N, 22°0.921'E, 139 m, ex gall Veronica anagallis-aquatica , 16.07.2012, leg. Toševski (3 larvae and 1 pupa) GoogleMaps .

Description of mature larva

(Figs 21A, B View Figure 21 , 22A-F View Figure 22 , 23A-C View Figure 23 ). Measurements (in mm). Body length: 2.25-2.46. The widest point in the body (meso- and metathorax) measures up to 1.20. Head width: 0.40-0.51.

General. Body elongate, slender, weakly curved, rounded in cross section (Fig. 21A View Figure 21 ).

Colouration. Head dark brown (Fig. 21B View Figure 21 ). All thoracic and abdominal segments white with many reddish or brown asperities (Fig. 21A View Figure 21 ).

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

Head capsule (Figs 21B View Figure 21 , 22A View Figure 22 ). Head suboval, flattened laterally, endocarinal line present, clearly extending to 1/3 of the length of frons. Frontal sutures on head very broad and distinct. Stemma, in the form of a very small pigmented spot with convex cornea. Des1 short, located in middle of central part of epicranium; des2 absent; relatively long des3 located anteriorly on epicranium close to border with frontal suture; des4 absent; des5 long, located anterolaterally (Fig. 22A View Figure 22 ). Fs1 absent; fs2 relatively long, located medially; fs3 absent; fs4 relatively long, located anteriorly; and fs5 long, located anterolaterally, close to antenna (Fig. 22A View Figure 22 ). Les1 and les2 as long as des5; ves short. Epicranial area with two postepicranial setae.

Antennae membranous and distinctly convex basal membranous article bearing one relatively long conical sensorium and four sensilla basiconica (Fig. 22B View Figure 22 ).

Clypeus (Fig. 22C View Figure 22 ) ~ 3-4 × as wide as long with two relatively long cls, located posterolaterally, without sensillum; fused to labrum.

Mouth parts. Labrum (Fig. 22C View Figure 22 ) ~ 4 × as wide as long, with three piliform lms, relatively long, almost of equal length; lms1 located anteromedially, lms2 partly located close to clypeus, and lms3 located anterolaterally. Epipharynx (Fig. 22D View Figure 22 ) with two very long digitate als, almost identical in length; with three ams of different length, ams1 and ams2 piliform and short, digitate ams3 and enlarged in middle; without mes; labral rods indistinct, irregular in shape. Mandibles (Fig. 22E View Figure 22 ) with two relatively long, piliform mds, located in distinct holes. Maxilla (Fig. 22F View Figure 22 ): stipes with one stps, two pfs and without mbs and sensillum, stps and pfs1 long, pfs2 relatively long; mala with four short digitate dms; three vms, different lengths, one seta very short, and two setae minute. Maxillary palpi with two palpomeres; length ratio of basal and distal palpomeres: 1:0.5. Praelabium (Fig. 22F View Figure 22 ) oval, with one long prms; ligula with sinuate margin and two very short ligs; premental sclerite broad, well visible. Postlabium (Fig. 22F View Figure 22 ) with two pms, pms1 absent, short pms2 located laterally and very long pms3 located medially; membranous area sparsely and finely asperate.

Thorax. Prothorax (Fig. 23A View Figure 23 ) with six long and two very short to minute prns, small pigmented dorsal sclerite present with two long prns, this sclerite subdivided into two triangular plates medially; two long ps; and two short to very short eus. Mesothorax (Fig. 23A View Figure 23 ) with two very short to minute prs, two long pds; one long as; one long and two very short to minute ss; one long eps; one long ps; and two short eus. Chaetotaxy of metathorax (Fig. 23A View Figure 23 ) almost identical to that of mesothorax. Each pedal area of thoracic segments well separated, with three long and one very short to minute pda.

Abdomen. Spiracles on abdominal segments I-VI close to the anterior margin and functional, spiracles on abdominal segment VII not functional, and abdominal segment VIII with atrophied spiracles. Abdominal segments I-VI (Fig. 23B, C View Figure 23 ) with one short and one minute prs; one long pds; one long and one very short to minute ss; one long eps; one relatively long ps; one short lsts; and two very short and sometimes one additional minute eus. Abdominal segments VII-VIII (Fig. 23C View Figure 23 ) with one very short prs; one long pds; one long and one very short to minute ss; one long eps; one relatively long ps; one short lsts; and two very short and sometimes one additional minute eus. Abdominal segment IX (Fig. 23C View Figure 23 ) with one relatively long ds; two relatively long ps; and one short to very short sts. Abdominal segment X (Fig. 23C View Figure 23 ) with one very short seta (ts).

Description of pupa

(Figs 24A-C View Figure 24 , 25A-C View Figure 25 ). Measurements (in mm). Body length: 2.24-2.73. Body width: 1.30-1.55. Thorax width: 0.82-0.88.

Body. Brownish, pronotal protuberances (p-pr) sclerotized, smooth; head, rostrum and pronotum darker than rest of body. Rostrum moderately slender. Pronotal protuberances fused at basis. Pronotum 2.2 × as wide as long. Mesonotum distinctly smaller than metanotum. Urogomphi short, conical, with sclerotized apices. Abdominal segment VIII with rounded, prominent abdominal protuberance dorsally (Fig. 25A, B View Figure 25 ).

Chaetotaxy. Sparse, setae short to medium, transparent. Head with one medium os. Rostrum with one rs (Fig. 25A View Figure 25 ). Pronotum with one elongate as, one ls, and four pls all almost equal in length. Dorsal parts of meso- and metathorax with two setae of various length, placed medially. Apices of femora with one medium-sized fes (Fig. 25A-C View Figure 25 ). Abdominal segments I-VIII with two medium-sized setae (one placed medially, the other laterally). Each lateral part of abdominal segments I-VIII with one medium-sized seta. Ventral parts of abdominal segments I-VIII with two medium-sized setae. Abdominal segment IX with two minute setae ventrally (Fig. 25A-C View Figure 25 ).

Biological notes.

The host plants of this species are several Veronica species: V. anagallis-aquatica L., V. anagalloides Guss., V. beccabunga L., V. catenata Pennell, V. scutellata L. ( Kleine 1910; Urban 1930; Hustache 1931; Hoffmann 1958; Sprick 1997). The adults appear on the host plants in May. The females oviposit during June in the ovarial tissue, inducing a bulbous gall in which the larva develops.

Remarks and comparative notes.

This species is common in the whole of Europe and Anatolia. The adult is closely related to G. miyoshii , a vicariant species living in eastern Asia ( Caldara 2008a; Alonso-Zarazaga et al. 2017). The immature stages confirm this relationship, as they share the postdorsal segment on the abdominal segments with one pds and the dorsal epicranium without des4.