Sibinia sicana Ragusa, 1908

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 : 172-176

Sibinia sicana Ragusa, 1908

Caldara, 1985: 85.

Material examined. 40 larvae from seeds of Gypsophila arrostii Guss. collected 2.vii.1989 at Aidone (Enna province, Sicily), leg. R. Caldara, and 6 (4 ♂♂, 2 ♀♀) 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: 0.48–0.53 mm (see Table. 1). Endocarinal line present, distinctly reaching middle of frons. Des1 very short, located close to frontal suture; des2 absent; des3 very long, located along frontal suture; des4 absent; des5 moderately long, located anterolaterally, des3 2.5 times as long as des5 ( Fig. 61 ). Fs1 and fs2 absent; fs3 minute, located medially; fs4 moderately long, located anteromedially (along epistoma); fs5 very long, located anterolaterally (along epistoma), fs5 2.5 times as long as fs4 ( Fig. 61 ). Les almost as long as des3; both ves short. Postepicranial area without pes and with 5 sensilla. Antennal segment membranous, bearing conical sensorium and 2 very short, conical, sensilla ( Fig. 64 ).

Clypeus ( Fig. 65 ) 3 times as wide as long; with 1 very short cls, and 1 sensillum, all located posterolaterally; anterior margin slightly rounded inside. Labrum ( Fig. 65 ) approximately 2.1 times as wide as long; lms1 distinctly shorter than lms2, and as long as lms3; anterior margin slightly sinuate. Epipharynx ( Fig. 66 ) with 2 long, finger-like als, different in length; with 3 short ams, in equal length; with 2 relatively short mes (see comments about ams and mes in Material and Methods); labral rods short, kidney-shaped, strongly converging posteriorly. Mandibles ( Fig. 63 ) with 1 very short mds. Maxilla ( Fig. 62 ): stipes with 1 very long stps, and with 2 very long pfs, of similar length; 1 very short mbs; mala with 4 slightly curved dms, different in length; with 3 moderately short vms, almost of equal length. Maxillary palpi: length ratio of basal and distal palpomeres 1:1.7; basal palpomera with 1 short mxps; distal palpomera with group of 3–4 conical, cuticular apical processes. Prementum ( Fig. 62 ) almost rounded, with 1 long prms; margin of ligula slightly curved inside; ligula with 1 ligs; premental sclerite clearly visible. Postmentum ( Fig. 62 ) with 2 pms, pms1 absent, moderately long pms2, 2 times as long as pms3.

THORAX AND ABDOMEN. Body length 2.60–3.00 mm (see Table. 1), elongate ( Fig. 67 ). Abdominal segments I– V almost equal in length, slightly larger than abdominal segment VI and VII ( Fig. 67 ). Spiracles on abdomen in median parts of segments (abdominal seg. I–VIII).

Chaetotaxy of body rather reduced. Setae long to very short and light yellow. Thorax. Prothorax ( Fig. 68 ) with 9 prn, 6 macro- and 3 microsetae; 2 long ps of same length; 1 short eus. Meso- and metathorax ( Fig. 68 ) with 1 moderately long prs; 2 long pds, similar in length; alar area with 1 long as; 1 long ss; 1 long eps; 2 moderately long ps, similar in length; and 1 short eus. Each pedal area of thoracic segments well-separated and with 2–3 moderately long to long pda. Abdomen. Abdominal segments I–VII ( Figs. 69, 70 ) with 1 long prs; 3 long pds of similar length, pds1 and pds3 slightly shorter than pds2; 2 ss of different length, ss1 very short to minute, ss2 moderately long; 2 long eps in equal length; 1 moderately long ps; 1 moderately long lsts; and 2 short eus. Abdominal segment VIII ( Fig. 70 ) with 1 short prs; 3 relatively short pds of similar length, pds1 and pds3 slightly shorter than pds2; 1 minute ss; 2 moderately long eps in equal length; 1 moderately long ps; 1 moderately long lsts; and 2 short eus. Abdominal segment IX ( Fig. 70 ) with 1 moderately long ds; 2 moderately long ps of similar length; and 2 moderately long sts in equal length. Anal lobes on abdominal segment X ( Fig. 70 ) without setae.

Description of pupa. COLORATION. Body white.

MORPHOLOGY ( Figs. 71–75 ). Body length 1.67–2.34 mm; widest part 1.16–1.40 mm (see Table. 2 ). Body moderately elongated. Rostrum medium long, approximately 3.1 times as long as wide, reaching almost to mesocoxae. Pronotum 1.37 times as wide as long.

CHAETOTAXY ( Figs. 71–75 ). Setae distinct, long, all equal in length (except on abdominal seg. IX), light, hairlike. Setae on abdominal segments I–VIII placed posteromedially and posterolaterally; all abdominal setae located on small, conical protuberances. Pseudocerci elongated, slightly curved to inside.

Biological observations. The host plant, Gypsophila arrostii Guss. , was previously unknown. It is an endemic species of southern Italy and Sicily. The larvae fed on seeds and, as with other species, left the capsule when mature. Pupation was observed 8 days after the larvae entered the soil. Adults were found in the cells 10 days later.

Remarks. With its host plant, this species is only found in southern Italy (Basilicata and Calabria) and Sicily and was considered very rare. However, adults were collected in large numbers on its flowering host plant in a season when typically in Sicily almost the whole herbs are dry and the collection of weevils by netting was unlikely to be conducted. Additionally, S. unicolor Fåhraeus, 1843 , which is a closely related species to S. sicana and is widely distributed in the central and Eastern Palaearctic, lives on Gypsophila ( G. paniculata L., G. papillosa Porta , and G. repens L.: Caldara 1985; Dieckmann 1988).

Figures

FIGURES 61 – 66. Sibinia sicana mature larva head, antenna and mouth parts: 61 — dorsal view (des — dorsal epicranial s., fs — frontal epicranial s., les — lateral epicranial s., ves — ventro epicranial s., st—stemmata, at—antenna); 62 — 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.); 63 — right mandible (mds — mandible dorsal s.); 64 — antenna; 65 — labrum and clypeus (cls — clypeal s., lms — labral s.); 66 — epipharynx (ams — anteromedial s., als — anterolateral s., mes — median s., lr—labral rods).

FIGURES 67 – 70. Sibinia sicana mature larva habitus: 67 — lateral view, 68 — lateral view of thoracic segments, 69 — lateral view of abdominal segment I, 70 — 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 71 – 75. Sibinia sicana pupa habitus: 71 — ventral view; 72 — detail of head; 73 — dorsal view; 74 — detail of pronotum; 75 — 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).