Tychius (s. str.) argentatus Chevrolat, 1859

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 : 18-19

Tychius (s. str.) argentatus Chevrolat, 1859

Caldara 1990: 172.

Material examined. 3 larvae obtained from pods of Lotus ornithopodioides L. collected 20.v.1979 on sand dunes near the sea at a little bay called Porto Ferro near Stintino , Sassari province, Sardinia ( Italy), leg. R. Caldara, and 2 pupae obtained 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 brown to dark yellow. All thoracic and abdominal segments light yellow to yellow.

HEAD CAPSULE AND MOUTH PARTS. Head width: 0.42–0.45 mm (see Table. 1 ). Endocarinal line present, relatively short. Des 1 located almost in central parts of epicarnium; des 2 located very near frontal suture, near des 3; des 3 located along frontal suture; des 4 located anterolaterally; des 5 located anterolaterally; des 2 and des 4 4 times shorter than others (des 1, des 3, des 5) ( Fig. 125 ). Fs 1 and fs 2 absent; fs 3 short, located medially; fs 4 located anteromedially (along epistoma); fs 5 located anterolaterally (along epistoma), both 3 to 4 times longer than fs 3 ( Fig. 125 ). Les almost as long as des 3. Ves very short. Post-epicranial area with group of 4 minute pes. Antennal segment membranous, bearing conical sensorium and 5 very short, conical, sensilla ( Fig. 128 ).

Labrum ( Fig. 129 ) approximately 2.15 times as wide as long; lms 3 slightly shorter than equal in length lms 2 and lms 1; anterior margin slightly sinuate. Clypeus ( Fig. 129 ) 2.7 times as wide as long; with 2 pairs of very short cls of same length, and 1 sensillum, all posterolaterally; anterior margin slightly rounded inside. Epipharynx ( Fig. 130 ) with 3 pairs of als, different in length; with 2 pairs of short and triangular ams; with 3 long and finger-like mes; labral rods short, kidney-shaped, and slightly converging posteriorly. Mandibles ( Fig. 127 ) with 2 short mds, almost of equal length. Maxilla ( Fig. 126 ): stipes with 1 stps; and with 2 pfs of equal length; mala with 4 straight dms, different in length; with 3 vms, short and almost of equal length. Maxillary palpi: length ratio of basal and distal palpomeres 1:1.7; basal palpomera with 1 short mpxs; distal palpomera with group of 3–4 conical, cuticular apical processes. Prementum ( Fig. 126 ) almost rounded, with 1 prms; margin of ligula slightly curved inside; ligula with 3 lig; premental sclerite distinct. Postmentum ( Fig. 126 ) with 3 pairs of pms, different in length.

THORAX AND ABDOMEN. Body length 2.7–3.4 mm (see Table. 1 ), elongate. Abdominal segments I–VI almost equal in length ( Fig. 131 ). Spiracles on abdomen in anteromedian parts of segments (abdominal seg. I–VIII).

Chaetotaxy of body rather reduced. Setae moderately long or short and light yellow. Thorax. Prothorax ( Fig. 132 ) with 7 prn, all macrosetae in different length; 2 moderately long ps of same length; 1 eus. Meso- and metathorax ( Fig. 132 ) with 1 prs; 3 pds, different in length; 1 ss; 1 eps; 1 ps and 1 eus. Each pedal area of thoracic segments well-separated and with 6 long pda. Abdomen. Abdominal segments I–VII ( Fig. 133 ) with 1 prs; 3 pds of different length; 2 ss of different length; 2 eps; 1 ps; 1 lsts; and 2 short eus. Abdominal segment VIII ( Fig. 134 ) with 3 pds of different length; 1 eps; 1 ps; 1 lsts; and 2 short eus. Abdominal segment IX ( Fig. 134 ) with 1 ds; 1 ps; and 1 sts. Anal lobes on abdominal segment X ( Fig. 134 ) with 1 very short, feebly visible seta.

Description of pupa. COLORATION. Body salmon.

MORPHOLOGY ( Figs. 135–137 ). Body length 2.3–2.5 mm; widest part 0.9–1.0 mm (see Table. 1 ). Body rather stocky. Rostrum long, approximately 4 times as long as wide, reaching mesocoxae. Pronotum 1.5 times as wide as long.

CHAETOTAXY ( Figs. 135–137 ). Setae distinct, moderately long, unequal in length, light brown; on pronotum and head placed on conical protuberances. Head capsule including 2 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, 2 ds, and 1 pls; ds as long as other setae on pronotum. Dorsal parts of meso- and metathorax with 1 seta. Each apex of femora with 2 fes of equal length. Setae on abdominal segments I–VIII placed medially and laterally; all abdominal setae located on small, conical protuberances. Pseudocerci slender, slightly curved inside.

Biological observations. On the same plant adult specimens of T. argentatus and T. capucinus were collected, although the latter in very poor number. However only adults of T. argentatus reared from pupae and all the collected immatures surely belong to a single species. Moreover these immatures showed morphological differences from larvae and pupae of T. capucinus collected elsewhere although the two species at these stages seem closely related. The plants were largely in flower and only 10 % of the pods collected were infested. The pupae were found in the cells 8 days after the entrance of larvae into the soil. The duration of the pupal stadium was 7 days. No adult left his cell during the following 30 days and they were removed artificially.

Remarks. Tychius argentatus is a common species with a circummediterranean distribution. It was quoted on several species of Lotus other than L. ornithopodioides L., as L. edulis L., L. creticus L. and L. tenuis W. et K., and is collected frequently also far from the sea both in plain and in mountains at low altitude.

Figures

FIGURES 125–130. Tychius argentatus mature larva head, antenna and mouth parts: 125—dorsal view (des—dorsal epicranial s., fs—frontal epicranial s., les—lateral epicranial s., ves—ventral epicranial s., pes—posterior epicranial s., st—stemmata, at—antenna); 126—right maxilla, dorsal view (dms—dorsal malar s., vms—ventral malar s., mpxs—maxillary palps s., pfs—palpiferal s., stps—stipital s.), prementum and postmentum, ventral view (prms—premental s., pms—postmental s., ligs—ligular s.); 127—right mandible (mds—mandible dorsal s.); 128—antenna; 129—labrum and clypeus (cls—clypeal s., lms—labral s.); 130—epipharynx (ams—anteromedial s., als—anteriolateral s., mes—median s., lr—labral rods).

FIGURES 131–134. Tychius argentatus mature larva habitus: 131—lateral view, 132—lateral view of thoracic segments, 133—lateral view of abdominal segment I., 134—lateral view of abdominal segments VIII–X (prns—pronotal s., prs—prodorsal s., pds—postdorsal 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 135–137. Tychius argentatus pupa habitus: 135—ventral view, 136—dorsal view, 137—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).