Sibinia tibialis Gyllenhal, 1835

Skuhrovec, Jiří, Gosik, Rafał, Caldara, Roberto & Košťál, Michael, 2015, Immatures of Palaearctic species of the weevil genus Sibinia (Coleoptera, Curculionidae): new descriptions and new bionomic data with suggestions on their potential value in a phylogenetic reconstruction of the genus, Zootaxa 2, pp. 151-187 : 163-164

Sibinia tibialis Gyllenhal, 1835

Caldara, 1985: 36.

Material examined. 12 larvae from seeds of Silene otites (L.) Wib. collected 5.viii. 2014 in southern Slovakia (Borská nížina, Malacky env. 150 m a. s. l., N 48°24.7´, E 17°04.0´), leg. J. Skuhrovec, M. Košťál & Z. Košťálová, and 7 (4 ♂♂, 3 ♀♀) pupae obtained from larvae collected similarly to the others, all determined by association with reared adults.

Differential diagnosis. See Key to the immatures of the Palaearctic species of the genus Sibinia and Table. 3 .

Description of mature larva. COLORATION. Head brown to dark yellow. All thoracic and abdominal segments light yellow.

HEAD CAPSULE AND MOUTH PARTS. Head width: 0.53–0.63 mm (see Table. 1). Endocarinal line present, reaching middle of frons. Des1 minute, located near frontal suture; des2 minute, located almost in central parts of epicarnium; des3 long, located along frontal suture; des4 absent; des5 long, located anterolaterally ( Fig. 31 ). Fs1 and fs2 absent; fs3 minute, located medially; fs4 long, located anteromedially (along epistoma); fs5 very long, located anterolaterally (along epistoma), fs5 1.5 times as long as fs4 ( Fig. 31 ). Les almost as long as des3; ves1 short and ves2 long. Postepicranial area with 1 pes and with 2–3 sensilla. Antennal segment membranous, bearing conical sensorium and 2 very short, conical, sensilla ( Fig. 34 ).

Clypeus ( Fig. 35 ) 3 times as wide as long; with 2 very short cls, and 1 sensillum, all located posterolaterally; anterior margin slightly rounded inside. Labrum ( Fig. 35 ) approximately 3.5 times as wide as long; lms1 distinctly shorter than lms2, and slightly longer and larger than lms3; anterior margin slightly sinuate. Epipharynx ( Fig. 36 ) with 2 elongated, finger-like als, similar in length; with 3 short ams, similar in length; with 2 very short and fingerlike mes (see comments about ams and mes in Material and Methods); labral rods elongate, kidney-shaped, strongly converging posteriorly. Mandibles ( Fig. 33 ) with 2 mds different in length. Maxilla ( Fig. 32 ): stipes with 1 long stps, and with 2 long pfs, almost of equal length, 1 very short mbs; mala with 4 slightly curved dms, different in length; with 3 very short vms, almost of equal length. Maxillary palpi: length ratio of basal and distal palpomeres 1:1.6; basal palpomera with 1 short mxps; distal palpomera with group of 3–4 conical, cuticular apical processes. Prementum ( Fig. 32 ) almost rounded, with 1 prms; margin of ligula slightly curved inside; ligula with 2 very short ligs; premental sclerite clearly visible. Postmentum ( Fig. 32 ) with 2 pms, pms1 absent, very long pms2, 4 times as long as pms3.

THORAX AND ABDOMEN. Body length 3.50–4.30 mm (see Table. 1), elongate ( Fig. 37 ). Abdominal segments I– V almost equal in length, slightly larger than abdominal segment VI and VII ( Fig. 37 ). Spiracles on abdomen in posterior parts of segments (abdominal seg. I–VIII).

Chaetotaxy of body rather reduced. Setae long to very short and light yellow. Thorax. Prothorax ( Fig. 38 ) with 10 prn, 9 macro- and 1 microsetae; 2 moderately long ps of same length; 1 eus. Meso- and metathorax ( Fig. 38 ) with 1 moderately long prs; 1 moderately long and 1 short pds; alar area with moderately long 1 as; 1 very short ss; 1 moderately long eps; 1 moderately long ps; and 1 eus. Each pedal area of thoracic segments well-separated and with 2 pda. Abdomen. Abdominal segments I–VII ( Figs. 39, 40 ) with 1 long prs; 3 pds of different length, pds1 and pds3 very short, pds2 long; 2 ss of different length, ss1 very short to minute, ss2 moderately long; 2 eps in equal length; 2 ps of different length, ps1 short and ps2 moderately long; 1 long lsts; and 2 moderately long eus. Abdominal segment VIII ( Fig. 40 ) with 1 moderately long prs; 3 pds of different length, pds1 and pds3 very short, pds2 moderately long; 1 very short to minute ss; 2 moderately long eps in equal length; 2 ps of different length, ps1 short and ps2 moderately long; 1 moderately long lsts; and 2 moderately long eus. Abdominal segment IX ( Fig. 40 ) with 2 ds of different length, ds1 short and ds2 moderately long; 2 ps of different length, ps1 very short and ps2 moderately long; and 2 moderately long sts in equal length. Anal lobes on abdominal segment X ( Fig. 40 ) with 2 minute setae.

Description of pupa. COLORATION. Body white.

MORPHOLOGY ( Figs. 41–45 ). Body length 2.35–3.00 mm; widest part 1.15–2.00 mm (see Table. 2 ). Body rather stocky. Rostrum moderately long, approximately 4 times as long as wide, reaching mesocoxae. Pronotum 1.6 times as wide as long.

CHAETOTAXY ( Figs. 41–45 ). Setae distinct, medium long, unequal in length, brown; on pronotum and head placed on small protuberances. Setae clearly visible, medium long, unequal in length, brown; on pronotum and head placed on small protuberances. Setae on head different in length, sos 3–4 times shorter than os; rs as long as pas ( Fig. 42 ). Ds2 slightly shorter than other setae on pronotum ( Fig. 44 ). Setae on abdominal segments I–VIII placed posteromedially and posterolaterally; all abdominal setae located on thorn-like protuberances. Pseudocerci short, triangular in shape.

Biological observations. The larvae fed on seeds, and mature larvae left the capsule and entered the soil to pupate. Pupation was observed 8–10 days after the larvae entered the soil. Adults were found in the cells 7–9 days later.

Remarks. This species is primarily distributed in Central Europe and reached northern France in the west and central Italy and Romania in the south. It is also reported to be in Asia and the Far East ( Caldara 1985, 2013). Sibinia tibialis seems monophagous on Silene otites (L.) Wib. ( Dieckmann 1988; Rheinheimer & Hassler 2010), although the adult was also collected on S. tatarica (L.) Pers. in Germany ( Neresheimer & Wagner 1939) and on Minuartia setacea (Thuill) Hayek in France ( Hoffmann 1955 under S. guillebeaui Desbrochers des Loges, 1897).

Figures

FIGURES 31 – 36. Sibinia tibialis mature larva head, antenna and mouth parts: 31 — dorsal view (des — dorsal epicranial s., fs — frontal epicranial s., les — lateral epicranial s., pes — posterior epicranial s., ves — ventro epicranial s., st—stemmata, atantenna); 32 — right maxilla, dorsal view (dms — dorsal malar s., vms — ventral malar s., mpxs — maxillary palps s., mbs — basioventral s., pfs — palpiferal s., stps — stipital s.), prementum and postmentum, ventral view (prms — premental s., pms — postmental s., ligs — ligular s.); 33 — right mandible (mds — mandible dorsal s.); 34 — antenna; 35 — labrum and clypeus (cls — clypeal s., lms — labral s.); 36 — epipharynx (ams — anteromedial s., als — anterolateral s., mes — median s., lr—labral rods).

FIGURES 37 – 40. Sibinia tibialis mature larva habitus: 37 — lateral view, 38 — lateral view of thoracic segments, 39 — lateral view of abdominal segment I, 40 — lateral view of abdominal segments VII—X (prns — pronotal s., prs — prodorsal s., pds — postdorsal s., as — alar s., ss — spiracular s., eps — epipleural s., ps — pleural s., pda — pedal s., lsts — laterosternal s., eus — eusternal s., ds — dorsal s., sts — sternal s., Th 1 – 3 — number of thoracic segments, Ab 1 – 10 — number of abdominal seg.).

FIGURES 41 – 45. Sibinia tibialis pupa habitus: 41 — ventral view; 42 — detail of head; 43 — dorsal view; 44 — detail of pronotum; 45 — lateral view (HW—head width; BW—body width; BL—body length; setae; as — apical s., d — dorsal s., ds — discal s., l — lateral s. on abdomen, ls — lateral s. on pronotum, os — orbital s., pas — postantennal s., pls — posterolateral s., sos — superorbital s., vs — vertical s.; pc—pseudocerci).