Larinus (Phyllonomeus) sturnus (Schaller, 1783)

Gosik, Rafał & Skuhrovec, Jiří, 2011, Descriptions of mature larvae and pupae of the genus Larinus (Coleoptera: Curculionidae, Lixinae), Zootaxa 3019, pp. 1-25 : 15-19

Larinus (Phyllonomeus) sturnus (Schaller, 1783)

Scherf 1964: 132 (key), 134–135 (description), Figs. 151–153; Nikulina et al. 2004: 25 (key).

Material. (77 larvae of different larval instars, 20 pupae), collected in the flower heads of cabbage thistle ( Cirsium oleraceum (L.) Scop.)) growing in wet meadows and in the flower heads of welted thistle ( Carduus crispus L.) growing in psammophilous grass communities: POLAND centr. or., wet meadow in Łąki ad Nałęczów, UTM nets: EB 88, 7. and 25.vi., 10. and 24.vi., 5. and 20.viii., 5.ix.2009 (65 larvae, 20 pupae); POLAND mer. or., wet meadow in Susiec, UTM nets: FA58, 20.viii.2009 (5 larvae); POLAND centr., sand grass communities in Stara Słupia, UTM nets: EB03, 12.vii.2009 (5 larvae); sand grass communities in Pińczów, UTM nets: DA69, 12.vii.2009 (2 larvae), all R. Gosik leg.

Differential diagnosis. Mature larva. Endocarina present (x L. pollinis ) ( Figs. 29, 30 ). Des 4 close to des 3 (x L. turbinatus ) ( Figs. 29, 30 ). Less than 15 setae on pronotum (x L. pollinis ) ( Fig. 37 ). Spiracular area in meso- and metathoax with three setae (x L. obtusus , L. pollinis , L. turbinatus ) ( Fig. 37 ). Abdominal segment I–VII with 1 prs, 7 pds, 2 dpls and 2 vpls (x L. obtusus , L. pollinis ) ( Fig. 38 ). Setae on thorax and abdomen long ( Figs. 37, 38 ) (x L. turbinatus ). Pupa. Sas on head as horns (x L. obtusus , L. pollinis , L. turbinatus ) ( Figs. 40, 41 ). Less than 15 setae on pronotum (x L. pollinis ) ( Fig. 41 ). Seta 1 on abdominal segment I. near anterior margin, remaining 8 setae close to posterior margin (x L. pollinis , L. turbinatus ) ( Fig. 41 ). Pc distinct and long (x L. obtusus , L. pollinis ) ( Figs. 40– 42 ).

Description of mature larva. COLORATION. Head brown or dark brown. All thoracic and abdominal segments white or light-yellow. Cuticle minutely spiculate.

HEAD CAPSULE AND MOUTH PARTS. Head width: 2.0–2.3 mm (mean 2.2 mm), oval, endocarinal line present, reaches middle of the frons. Des 1 and des 3 located almost on frontal suture, des 2 and des 4 located in central part of epicranium, des 5 placed anterolaterad, of equal length ( Figs. 29, 30 ). Fs 1, fs 2 and fs 3 placed medially, fs 4 and fs 5 located posterolaterad, of equal length ( Figs. 29, 30 ). Les 1, 2 and ves slightly shorter than des. Epicranial area with group of 4 pores; one pore near des 1, the next close des 2, remaining two pores placed laterally. Antenna with sensorium conical triangular, relatively short, located medially; basal membranous article with 3 triangular sensillae ( Fig. 31 ).

Labrum ( Fig. 32 —left side) approx. 2.3 times as wide as long with 3 pairs of hairform lrms 1-3 of different length; lrms 2 3 times shorter than lrms 1 and lrms 3; anterior margin double sinuate. Clypeus ( Fig. 32 —left side) 2.3 times as wide as long with 3 pairs of short cls 1-3 of unequal length, located posterolaterad; cls 1 3 times shorter than cls 2 and cls 3; anterior margin slightly rounded to the inside. Epipharynx ( Fig. 32 —right side) with 5 pairs of blunt, finger-like als of different length; 2 pairs of ams, ams 2 distinctly longer than ams 1; two pairs of mes, triangular, blunt; labral rods (lr) easily visible, very long, strong converging posteriorly. Mandibles ( Fig. 33 ) slightly truncate; mds 1, 2 almost of equal length. Maxilla ( Fig. 34 ): stipes with 2 stps 1, 2, 2 pfs 1, 2 and 1 mbs of different length; mala with 7 slightly curved dms, different in length; vms 1-4 short, almost of equal length; vms distinctly shorter than dms. Maxillary palpi with two palpomeres; without maxillary palpi seta; length ratio of basal and distal palpomeres: 1:0.7; distal palpomere with group of 6 conical, cuticular apical processes. Praelabium ( Fig. 35 ) heart-shaped, with a pair of plbs; margin of ligula slightly curved to the inside, ligs 1-3 sharp, short; premental sclerite well visible. Labial palpi with two palpomeres; length ratio of basal and distal palpomeres, 1:0.6; distal palpomere with 4 conical cuticular apical processes; both palpomeres with 1 dorsal pore. Postlabium ( Fig. 35 ) with 3 pairs of pslbs, different in length, located laterally and anterolaterally.

THORAX AND ABDOMEN. Body length: 13.5–20.5 mm (mean 17.5 mm) elongated, curved ( Fig. 36 ). The widest place in the body (metathorax) up to 4.0 mm. Abdominal segments I–IV almost equal in length, slightly smaller than abdominal segments V–VI; next abdominal segments decreasing gradually to the terminal parts of the body. Spiracles on the abdomen in median parts of abdominal segments I–VIII ( Fig. 38 ).

Chaetotaxy of the body rather reduced. Setae medium long, light yellow. Thorax. Prothorax ( Fig. 37 ) with 11 prns, 2 dpls, 2 vpls and 1 msts. Mesothorax ( Fig. 37 ) with 1 prs, 5 pds, 1 alar s., 3 ss unequal in length, 1 dpls, 2 vpls and 1 msts. Chaetotaxy of metathorax ( Fig. 37 ) similar to mesothoracal. Each pedal area of thoracic segments well separated, with 4 long and 3 short pda. Abdomen. Abdominal segments I–VII ( Fig. 38 ) with 1 prs, 7 pds, 1 dls, 1 ss in the spiracular area, 2 dpls, 2 vpls, 1 lsts and 2 short msts. Abdominal segment VIII ( Fig. 39 ) with 7 pds, 2 dpls, 2 vpls, 1 lsts and 2 short msts. Abdominal segment IX ( Fig. 39 ) with 6 ds, 3 ls of different length and 3 sts of different length. All anal lobes on abdominal segment X ( Fig. 39 ) without setae.

Description of pupa. COLORATION. Body white-gray or yellowish. The cuticle minutely spiculate, light yellow in the vicinity of the bases of setae.

MORPHOLOGY ( Figs. 40–42 ). Body length: 10.2–12.5 mm, in the widest region: 5.3–5.9 mm. Body elongated, slender. Rostrum long, approx 2.7 times as long as wide, reaching up to the metacoxae. Antennae relatively long and slender. Pronotum 1.6 times as wide as long. Abdominal segments I–IV of equal length; next abdominal segments diminish gradually to the end of the body. Abdominal segment VIII almost semicircular; IX distinctly smaller than other abdominal segments.

CHAETOTAXY ( Figs. 40–42 ). Setae distinct, medium long, unequal in length, on pronotum placed on protuberances. Head capsule includes 2 vs, 2 sos, 1 os and 4 pas. Rostrum with 5 rs, 2 setae placed medially, remaining 3 setae on anterior margin of rostrum. There is also a seta on each of mandibular thecae (mts). Setae on head and rostrum straight, shorter than setae on thoracic and abdominal segments. Pronotum with 1 pair of superapical setae (sas) placed on conical, divided protuberances; 5 pairs of lateral setae (ls 1-5); 2 pairs of discal setae (ds 1, 2); 1 pair of superlateral setae (sls) and 4 pairs of posterolateral setae (pls 1-4). Dorsal parts of mesothorax with 1 pair of setae placed posteromedially and the next 5 pairs distributed along its anterior margin. Chaetotaxy of metathorax similar to mesothoracal. Each apex of femora with groups of 3 fes. Bases of setae with light yellow ring. Dorsal parts of each of abdominal segments I–VIII with 1 pair of setae placed posteromedially and 8 pairs located along its anterior margin. Setae on abdominal segments VII, VIII placed on conical protuberances. Abdominal segments I–VIII with groups of 4 lateral setae and 3 short ventral setae in regular lines. Abdominal segment IX with 4 pairs of ventral micro-setae and a pair of short, thin dorsal setae. Pseudocerci elongated, slightly curved to the inside.

Remarks. Measurements presented by Scherf (1964) did not agree with our results; body length of larvae 13– 15 mm (ours, 19–26 mm) and body length of pupae 12–14 mm (ours, 10.2–12.5 mm). This difference could be caused by different quality of measurements, method of measurement and/or because the thorax and abdomen are not sclerotized and may also be affected by the fixation process, and body length and width are given only for comparison here ( Table. 1 ). Scherf (1964) did not give any other measurements (e.g. head and/ or body width). Chaetotaxy is almost the same apart from a few details, e.g. count of les. Scherf (1964) recorded the presence of three les, but unlike he, we recorded two setae in this region. Descriptions of larvae and also of pupae by Scherf (1964) are brief but informative. Unfortunately, we can not say the same about drawings, which are very poor and almost without any information. Nikulina et al. (2004) mentioned this species only in their key, which is reproduced from Scherf (1964).

Figures

FIGURES 29 – 35. Larinus sturnus mature larva head, antenna and mouth parts: 29 — dorsal view, 30 — lateral view (des — dorsal epicranial s., fs — frontal s., les — lateral epicranial s., ves — ventral epicranial s., at — antenna, st — stemma), 31 — antenna, 32 (left side) — labrum and clypeus (cls — clypeal s., lrms — labral s.), 32 (right side) epipharynx (ams — anteromedial s., als — anterolateral s., mes — median s., lr — labral rods), 33 — right mandible (mds — mandible dorsal s.), 34 — right maxilla, dorsal view (dms — dorsally malae s., vms — ventrally malae s., pfs — palpiferal s., stps — stipal s., mbs — malar basiventral s.), 35 — praelabium and postlabium, ventral aspect (plbs — prelabial s., pslbs — postlabial s., ligs — ligular s.).

FIGURES 36 – 39. Larinus sturnus mature larva habitus: 36 — lateral view, 37 — lateral view of thoracic segments, 38 — lateral view of first abdominal segment, 39 — lateral view of abdominal segments VIII – X (prns — pronotal s., dpls — dorsopleural s., vpls — ventropleural s., prs — prodorsal s., pds — postdorsal s., pda — pedal s., as — alar s., ss — spiracular s., dls — dorsolateral s., lsts — laterosternal s., msts — mesosternal s., sts — sternal s., ls — lateral s., ds — dorsal s.).

FIGURES 40 – 42. Larinus sturnus pupa habitus: 40 — ventral view, 41 — dorsal view, 42 — lateral view (pc — pseudocerci, sas — super apical s., ls — lateral s., sls — super lateral s., ds — discal s., pls — posterolateral s., vs — vertical s., sos — super orbital s., os — orbital s., pas — postantennal s., rs — rostral s., mts — mandibular thecae s., fes — femoral s.).