Larinus (Larinomesius) obtusus Gyllenhal, 1835

Gosik, Rafał & Skuhrovec, Jiří, 2011, Descriptions of mature larvae and pupae of the genus Larinus (Coleoptera: Curculionidae, Lixinae), Zootaxa 3019, pp. 1-25 : 6-10

Larinus (Larinomesius) obtusus Gyllenhal, 1835

Material. (11 larvae of different larval instars, 7 pupae), collected in flower heads of spotted knapweed ( Centaurea stoebe L.) growing in psammophilous grass communities: POLAND centr. or., Wołczyny ad Włodawa, UTM nets: FC80, 28.viii.2008 (4 larvae, 3 pupae); Stare Stulno ad Włodawa, UTM nets: FC80, 28.viii.2008 (3 larvae, 1 pupa), all R. Gosik leg; collected in flower heads of wig knapweed ( Centaurea phrygia L.) growing in meadow under mountains: ROMANIA, prov. Alba, Rimetea, 33 km S of Cluj, Bachufer, N 46°28'57", E 23°34'64", 480 m a.s.l., 21.vii.2008 (4 larvae, 3 pupae), J. Skuhrovec leg.

Differential diagnosis. Mature larva. Endocarina present (x L. pollinis ) ( Figs. 1, 2 ). Des 4 close to des 3 (x L. turbinatus ) ( Figs. 1, 2 ). Less than 15 setae on pronotum (x L. pollinis ) ( Fig. 9 ). Spiracular area in meso- and metathoax with one only seta (x L. pollinis , L. sturnus , L. turbinatus ) ( Fig. 9 ). Abdominal segments I-VII without prs, only 5 pds, and 1 dpls (x L. pollinis , L. sturnus , L. turbinatus ) ( Fig. 10 ). Setae on thorax and abdomen long ( Figs. 9, 10 ) (x L. turbinatus ). Pupa. Sas on head, no protuberance with a shape such as horns (x L. sturnus ) ( Figs. 12, 13 ). Less than 15 setae on pronotum (x L. pollinis ) ( Fig. 13 ). Seta 1 on abdominal segment I. near the anterior margin, remaining 7 setae close to the posterior margin (x L. pollinis , L. turbinatus ) ( Fig. 13 ). Pc very short (x L. sturnus , L. turbinatus ) ( Figs. 12, 14 ).

Description of mature larva. COLORATION. Head light brown or brown. All thoracic and abdominal segments white or gray. Cuticle minutely spiculated.

HEAD CAPSULE AND MOUTH PARTS. Head width: 1.0-1.3 mm (mean 1.1 mm), suboval, oblate laterally, endocarinal line present, reaches middle of the frons. Des 1 and des 2 located in the central part of epicranium, des 3 near to frontal suture, des 4 and des 5 located anterolaterad, equal in length ( Figs. 1, 2 ). Fs 1, fs 2 and fs 3 placed medially, fs 4 and fs 5 located laterally, close to epistoma, equal in length ( Figs. 1, 2 ). Les 1, 2 and ves 1, 2 slightly shorter than des. Epicranial area with group of 4 pores, one pore placed near to des 1, two pores placed laterally, one located apically. Antenna with sensorium conical triangular, relatively long, located latero-posteriad; basal membranous article with 6 triangular sensillae ( Fig. 3 ).

Labrum ( Fig. 4 —left side) approx. 2 times as wide as long, with 3 pairs of long, bacilliform lrms, of different length; lrms 3 shorter than lrms 1 and lrms 2, all lrms placed distinctly on protuberances; anterior margin double sinuate. Clypeus ( Fig. 4 —left side) 3.2 times as wide as long with 2 long, bacilliform cls, unequal in length, localized posterolaterad; anterior margin slightly rounded to the inside; median part covered by thorn-shaped cuticular processes. Epipharynx ( Fig. 4 —right side) with 5 pairs of blunt, finger-like als, different in length; 2 pairs of ams, ams 1 distinctly longer than ams 2; 2 pairs of short, blunt mes; labral rods (lr) elongated, converging anteriad. Mandibles ( Fig. 5 ) slightly truncate; mds short, hairform. Maxilla ( Fig. 6 ) stipes with 1 stps, 2 pfs and 1 malar basiventral s. (mbs), equal in length; mala with 10 bacilliform dms of different length; vms 1-2 short, almost equal in length; vms distinctly shorter than dms. Maxillary palpi with two palpomeres; basal palpomere with 1 mxps and two pores; length ratio of basal and distal palpomeres: 1:0.8; distal palpomere with a group of 6 long, conical, cuticular apical processes. Praelabium ( Fig. 7 ) heart-shaped, with 1 pair of plbs; ligula with sinuate margin and 3 pairs of hairform micro ligs, equal in length; premental sclerite well visible. Labial palpi with two palpomeres; length ratio of basal and distal palpomeres: 1:0.5; distal palpomere with 4 short, cuticular apical processes; basal palpomere with 1 dorsal pore. Postlabium ( Fig. 7 ) with 3 pslbs, different in length, the first pair localized anteriorly, remaining two pairs laterally.

THORAX AND ABDOMEN. Body length: 4.5–7.0 mm (mean 6.0 mm) stocky, slightly curved, rounded in cross section ( Fig. 8 ). The widest place in the body (mesothorax) measuring up to 2.0 mm. Metathorax and abdominal segments I–VI almost of equal length, next abdominal segments decreasing gradually to the terminal parts of the body. Spiracles on abdomen in median parts of abdominal segments I–VIII ( Figs. 9, 10 ).

Chaetotaxy of the body strongly reduced, poorly distinguished. Setae thin, short, light yellow. Thorax. Prothorax ( Fig. 9 ) with 10 prns unequal in length, 2 dpls, 2 vpls and 1 msts. Mesothorax ( Fig. 9 ) with 1 prs, 5 pds, 1 as, 1 ss, 3 dpls of different length, 1 vpls and 1 msts. Chaetotaxy of metathorax ( Fig. 9 ) similar to mesothoracal. Each pedal area of thoracic segments well separated, with 5 pda unequal in length. Abdomen. Abdominal segments I- VII ( Fig. 10 ) with 5 pds, 1 dls, 1 dpls, 1 vpls, 1 lsts and 1 short msts. Abdominal segment VIII ( Fig. 11 ) with 4 pds almost in equal length, 1 dls, 1 dpls, 1 vpls, 1 lsts and 1 short msts. Abdominal segment IX ( Fig. 11 ) with 3 relatively long ds, 2 ls and 3 sts of different lengths. Each anal lobe on abdominal segment X ( Fig. 11 ) with 2 microsetae.

Description of pupa. MORPHOLOGY ( Figs. 12–14 ). Body length: 5.5–5.6 mm, at the widest region: 3.3–3.4 mm. Body stocky, slightly curved, white or yellowish. Cuticle smooth. Rostrum short, approximately 1.1 times as long as wide, extended beyond procoxae. Antennae long and slender. Pronotum almost 2.2 times as wide as long. Abdominal segments I-V almost of equal length; abdominal segment VI semicircular, next abdominal segments diminish gradually to the end of the body. Abdominal segments VII-IX distinctly smaller than other abdominal segments.

CHAETOTAXY ( Figs. 12–14 ). Setae short, unequal in length, light yellow, on pronotum located on small protuberances. Head capusle includes 1 vs, 2 sos, 1 os and 4 pas. Rostrum with 2 rs, both located on the anterior margin of the rostrum. There is also a seta on each of mandibular thecae (mts). Setae on head capsule and rostrum straight, almost of the same length, slightly longer than setae on thoracic and abdominal segments. Pronotum with 1 sas, located on conical, curved protuberances, 5 ls, 2 ds, 1 sls and 4 pls. Dorsal parts of mesothorax with 1 pair of setae located posteromedially and 5 pairs located along its anterior margin. Chaetotaxy of metathorax similar to mesothoracal. Each apex of femora with groups of 3 fes. Dorsal parts of abdominal segments I-VIII with 2 pairs of setae located posteriorly and 7 pairs located along its anterior margin. Setae on abdominal segments VII, VIII placed on thorn-like protuberances. Abdominal segments I-VIII with groups of 4 lateral setae and 3 pairs of short ventral setae, in regular lines. Abdominal segment IX with 2 pairs of ventral micro-setae and 1 pair short, thin dorsal setae. Pseudocerci very short, triangular.

Figures

FIGURES 1 – 7. Larinus obtusus mature larva head, antenna and mouth parts: 1 — dorsal view, 2 — lateral view (des — dorsal epicranial s., fs — frontal s., les — lateral epicranial s., ves — ventral epicranial s., at — antenna), 3 — antenna, 4 (left side) — labrum and clypeus (cls — clypeal s., lrms — labral s.), 4 (right side) epipharynx (ams — anteromedial s., als — anterolateral s., mes — median s., lr — labral rods), 5 — right mandible (mds — mandible dorsal s.), 6 — left maxilla, dorsal view (dms — dorsally malae s., vms — ventrally malae s., mxps — maxillary palps s., pfs — palpiferal s., stps — stipal s., mbs — malar basiventral s.), 7 — praelabium and postlabium, ventral aspect (plbs — prelabial s., pslbs — postlabial s., ligs — ligular s.).

FIGURES 8 – 11. Larinus obtusus mature larva habitus: 8 — lateral view, 9 — lateral view of thoracic segments, 10 — lateral view of abdominal segment II., 11 — 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 — spicular s., dls — dorsolateral s., lsts — laterosternal s., msts — mesosternal s., sts — sternal s., ls — lateral s., ds — dorsal s.).

FIGURES 12 – 14. Larinus obtusus pupa habitus: 12 — ventral view, 13 — dorsal view, 14 — 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.).