Tychius (s. str.) curtirostris Desbrochers, 1873

Skuhrovec, Jiří, Gosik, Rafał & Caldara, Roberto, 2014, Immatures of Palaearctic species of the weevil genus Tychius (Coleoptera, Curculionidae): new descriptions and new bionomic data with an evaluation of their value in a phylogenetic reconstruction of the genus, Zootaxa 3839 (1), pp. 1-83 : 20-21

Tychius (s. str.) curtirostris Desbrochers, 1873

Caldara 1990: 192.

Material examined. 33 larvae from pods of Trifolium glomeratum L. collected 5.vii.1982 at Levanto , La Spezia province, Liguria (northern Italy), leg. R. Caldara, and 7 pupae reared from larvae collected contemporaneously together with the others, all determined by association with reared adults.

Differential diagnosis. See Tables 2 and 3 .

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

HEAD CAPSULE AND MOUTH PARTS. Head width: 0.28–0.35 mm (see Table. 1 ). Endocarinal line present, exceeding middle of frons. Des 1 located very near frontal suture; des 2 absent; des 3 located along frontal suture; des 4 located anterolaterally; des 5 located laterally; des 4 5 times shorter than des 1, des 3 and des 5 ( Fig. 151 ). Fs 1 and fs 2 absent; fs 3 very short, located medially; fs 4 located anteromedially (along epistoma); fs 5 located anterolaterally (along epistoma), 6 times longer than fs 3 ( Fig. 151 ). Les distinctly shorter than des 3. Ves very short. Post-epicranial area with group of 3 minute pes. Antennal segment membranous, bearing conical sensorium and 2 very short, conical, sensilla ( Fig. 154 ).

Labrum ( Fig. 155 ) approximately 3.1 times as wide as long; lms 1 slightly longer than equal in length lms 2 and lms 3; anterior margin rounded. Clypeus ( Fig. 155 ) 3.25 times as wide as long; with 2 pairs of very short cls of same length, and 1 sensillum, all posterolaterally; anterior margin almost straight. Epipharynx ( Fig. 156 ) with 2 pairs of als, different in length; with 2 pairs of short ams; with 2 relatively short finger-like and 1 short mes; labral rods short, kidney-shaped, slightly converging posteriorly. Mandibles ( Fig. 153 ) with 2 short mds, almost of equal length. Maxilla ( Fig. 152 ): stipes with 1 stps, 2 pfs of different length, and 1 mbs, distinctly shorter than pfs; mala with 4 straight dms, different in length; with 4 vms, moderately long and almost of equal length. Maxillary palpi: length ratio of basal and distal palpomeres 1:1.4; basal palpomera with 1 short mpxs; distal palpomera with group of some conical, cuticular apical processes. Prementum ( Fig. 152 ) heart-shaped, with 1 prms; margin of ligula slightly rounded; ligula with 2 ligs; premental sclerite distinct. Postmentum ( Fig. 152 ) with 3 pairs of pms, different in length.

THORAX AND ABDOMEN. Body length 1.6–2.4 mm (see Table. 1 ), moderately elongate. Abdominal segments I- III slightly smaller than abdominal segments IV–VI ( Fig. 157 ). Spiracles on abdomen in anteromedian parts of segments (abdominal segments I–VIII).

Chaetotaxy of body rather reduced. Setae moderately short or very short and light yellow. Thorax. Prothorax ( Fig. 158 ) with 7 prn, 6 macro- and 1 microsetae; 2 moderately long ps of same length; 1 eus. Mesothorax ( Fig. 158 ) with 1 prs; 3 pds, different in length; alar area with 1 very short as; 1 very short ss; 1 eps; 1 ps; and 1 short eus. Chaetotaxy of metathorax almost identical to that of mesothorax, on metathorax only 2 pds. Each pedal area of thoracic segments well-separated and with 3 pda, equal in length (moderately long). Abdomen. Abdominal segments I–VII ( Fig. 159 ) with 1 prs; 2 pds of different length; 2 very short ss; 2 eps of different length; 2 ps of different length; 1 lsts; and 2 short eus. Abdominal segment VIII ( Fig. 160 ) with 2 pds; 1 very short ss; 2 eps of different length; 2 ps of different length; 1 lsts; 2 short eus. Abdominal segment IX ( Fig. 160 ) with 1 ds; 2 very short ps; and 1 sts. Anal lobes on abdominal segment X ( Fig. 160 ) with 1 very short, feebly visible seta.

Description of pupa. COLORATION. Body whitish yellow.

MORPHOLOGY ( Figs. 161–163 ). Body length 1.7–2.2 mm; widest part 0.7–1.0 mm (see Table. 1 ). Body elongate, slender. Rostrum long, approximately 4.5 times as long as wide, reaching mesocoxae. Pronotum 1.4 times as wide as long.

CHAETOTAXY ( Figs. 161–163 ). Setae distinct, long or moderately long, unequal in length, light brown; on pronotum and head placed on small protuberances. Head capsule including 1 vs, 1 os, and 1 pas. Rostrum with 1 rs located medially. Vs and os as long as setae on pronotum, distinctly longer than pas and rs. Pronotum with 2 as, 2 ls, 1 ds, and 1 pls; ds distinctly smaller than other setae on pronotum. Dorsal parts of meso- and metathorax with 1 seta. Each apex of femora with 1 fes. Setae on abdominal segments I–VIII placed medially and laterally; all abdominal setae located on small, conical protuberances. Pseudocerci short, slightly curved inside.

Biological observations. Pupae were observed 7 days after the entrance of larvae into the soil. The duration of the pupal stage was 7 days. Adults emerged at the surface 3 days later.

Remarks. Tychius curtirostris is a common species with a circummediterranean distribution and is easily confused with T. pusillus ( Caldara 1975, 1990). In the same field, where T. curtirostris was collected, T. tibialis was collected also, but living on T. incarnatum L.

Figures

FIGURES 151–156. Tychius curtirostris mature larva head, antenna and mouth parts: 151—dorsal view (des—dorsal epicranial s., fs—frontal epicranial s., les—lateral epicranial s., ves—ventral epicranial s., pes—posterior epicranial s., at—antenna); 152—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.); 153—right mandible (mds—mandible dorsal s.); 154—antenna; 155—labrum and clypeus (cls—clypeal s., lms—labral s.); 156—epipharynx (ams—anteromedial s., als—anteriolateral s., mes—median s., lr—labral rods).

FIGURES 157–160. Tychius curtirostris mature larva habitus: 157—lateral view, 158—lateral view of thoracic segments, 159—lateral view of abdominal segment I., 160—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.).

FIGURES 161–163. Tychius curtirostris pupa habitus: 161—ventral view, 162—dorsal view, 163—lateral view (vs—vertical s., os—orbital s., pas—postantennal s., rs—rostral s., as—apical s., ls—lateral s., ds—discal s., pls—posterolateral s., fes—femoral s., pc—pseudocerci).