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

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https://doi.org/ 10.11646/zootaxa.3839.1.1

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Tychius (s. str.) argentatus Chevrolat, 1859


Tychius (s. str.) argentatus Chevrolat, 1859 View in CoL

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 View TABLE 2 and 3 View TABLE 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 View 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 View FIGURES 125–130 ). 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 View FIGURES 125–130 ). 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 View FIGURES 125–130 ).

Labrum ( Fig. 129 View FIGURES 125–130 ) 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 View FIGURES 125–130 ) 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 View FIGURES 125–130 ) 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 View FIGURES 125–130 ) with 2 short mds, almost of equal length. Maxilla ( Fig. 126 View FIGURES 125–130 ): 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 View FIGURES 125–130 ) almost rounded, with 1 prms; margin of ligula slightly curved inside; ligula with 3 lig; premental sclerite distinct. Postmentum ( Fig. 126 View FIGURES 125–130 ) with 3 pairs of pms, different in length.

THORAX AND ABDOMEN. Body length 2.7–3.4 mm (see Table. 1 View TABLE 1 ), elongate. Abdominal segments I–VI almost equal in length ( Fig. 131 View FIGURES 131–134 ). 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 View FIGURES 131–134 ) with 7 prn, all macrosetae in different length; 2 moderately long ps of same length; 1 eus. Meso- and metathorax ( Fig. 132 View FIGURES 131–134 ) 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 View FIGURES 131–134 ) 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 View FIGURES 131–134 ) with 3 pds of different length; 1 eps; 1 ps; 1 lsts; and 2 short eus. Abdominal segment IX ( Fig. 134 View FIGURES 131–134 ) with 1 ds; 1 ps; and 1 sts. Anal lobes on abdominal segment X ( Fig. 134 View FIGURES 131–134 ) with 1 very short, feebly visible seta.

Description of pupa. COLORATION. Body salmon.

MORPHOLOGY ( Figs. 135–137 View FIGURES 135–137 ). Body length 2.3–2.5 mm; widest part 0.9–1.0 mm (see Table. 1 View 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 View FIGURES 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.


Departamento de Geologia, Universidad de Chile













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