Tychius (s. str.) depressus 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 : 12-13

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

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Tychius (s. str.) depressus Desbrochers, 1873


Tychius (s. str.) depressus Desbrochers, 1873 View in CoL

Caldara 1990: 147.

Material examined. 2 larvae from pods of Medicago polymorpha collected 20.v.1979 at Fertilia , Sassari, 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.

HEAD CAPSULE AND MOUTH PARTS. Head width: 0.44–0.48 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 absent; des 5 located anterolaterally; des 2 4 times shorter than others (des 1, des 3, des 5) ( Fig. 60 View FIGURES 60–65 ). Fs 1 and fs 2 absent; fs 3 short, located posteromedially; fs 4 located anteromedially (along epistoma); fs 5 located anterolaterally (along epistoma), 3 to 4 times longer than fs 3 ( Fig. 60 View FIGURES 60–65 ). Les almost equal in length as des 3. Ves very short. Post-epicranial area with 2 minute pes. Antennal segment membranous, bearing conical sensorium and 4 very short, conical, sensilla ( Fig. 63 View FIGURES 60–65 ).

Labrum ( Fig. 64 View FIGURES 60–65 ) approximately 3 times as wide as long; lms 1 and lms 2 longer than lms 3; anterior margin slightly curved inside. Clypeus ( Fig. 64 View FIGURES 60–65 ) 3.5 times as wide as long; with 2 pairs of short cls different in length, and 1 sensillum, all located posterolaterally; anterior margin slightly rounded. Epipharynx ( Fig. 65 View FIGURES 60–65 ) with 2 pairs of als, almost of equal length; with 2 pairs of short ams, ams 1 distinctly longer than ams 2, with 2 long finger-like and 1 short mes; labral rods relatively long, kidney-shaped, converging posteriorly. Mandibles ( Fig. 62 View FIGURES 60–65 ) with 2 short mds, almost of equal length. Maxilla ( Fig. 61 View FIGURES 60–65 ): stipes with 1 stps, with 2 pfs of equal length, and 1 mbs, distinctly shorter than pfs, and 1 sensillum; mala with 4 slightly curved dms, different in length; with 3 vms, short and almost of equal length. Maxillary palpi: length ratio of basal and distal palpomeres 1:1.6; basal palpomera with 1 short mpxs; distal palpomera with group of 3–4 conical, cuticular apical processes. Prementum ( Fig. 61 View FIGURES 60–65 ) almost rounded, with 1 prms; margin of ligula rounded; ligula with 1 lig; premental sclerite distinct. Postmentum ( Fig. 61 View FIGURES 60–65 ) with 3 pairs of pms, almost of equal length.

THORAX AND ABDOMEN. Body length 3.7–4.3 mm (see Table. 1 View TABLE 1 ), elongate. Abdominal segments I–VI almost of equal length ( Fig. 66 View FIGURES 66–69 ). Spiracles on abdomen in anteromedian parts of segments (abdominal segments I–VIII).

Chaetotaxy of body reduced. Setae moderately short or very short, and light yellow. Thorax. Prothorax ( Fig. 67 View FIGURES 66–69 ) with 9 prn, 6 macro- and 3 microsetae; 2 moderately long ps of same length; 1 eus. Meso- and metathorax ( Fig. 67 View FIGURES 66–69 ) with 1 prs; 3 pds, different in length; alar area with 1 as; 1 ss; 1 eps; 1 ps; and 1 short eus. Each pedal area of thoracic segments well-separated and with 3 pda, different in length (long, moderately long, short). Abdomen. Abdominal segments I–VII ( Fig. 68 View FIGURES 66–69 ) with 1 prs; 2 pds of different length; 2 ss of different length; 1 eps; 1 ps; 1 lsts; and 2 short eus. Abdominal segment VIII ( Fig. 69 View FIGURES 66–69 ) with 1 prs; 1 pds;. 2 ss of different length; 1 eps; 1 ps; 1 lsts; and 2 short eus. Abdominal segment IX ( Fig. 69 View FIGURES 66–69 ) with 1 ds; 1 ps; and 1 sts. Each anal lobe on abdominal segment X ( Fig. 69 View FIGURES 66–69 ) with 1 very short, feebly visible seta.

Description of pupa. COLORATION. Body salmon.

MORPHOLOGY ( Figs 70–72 View FIGURES 70–72 ). Body length 2.4–2.6 mm; widest part 1.2–1.3 mm (see Table. 1 View TABLE 1 ). Body rather stocky. Rostrum moderately long, approximately 4 times as long as wide, reaching mesocoxae. Pronotum 1.8 times as wide as long.

CHAETOTAXY ( Figs 70–72 View FIGURES 70–72 ). Setae distinct, 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 without setae. Vs as long as setae on pronotum, distinctly longer than os and pas. Pronotum with 2 as, 1 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. Only 5 % of collected pods were infested by larvae. Also the adults were not numerous on the flowering plants. Pupation was observed 8 days after the introduction of the larvae in the soil. Adults were observed in the cells 10 days later and emerged after a few days.

Remarks. Tychius depressus is an uncommon species known from central and southern Italy, Sicily, Sardinia, Corsica and northern Africa. It seems monophagous on Medicago polymorpha L. since it was collected on the same plant also in central Italy ( Caldara 1990). The T. depressus group is composed of six species distributed in the eastern Mediterranean region and in Southwestern Asia. There are no biological data on the other five species of the group.


Departamento de Geologia, Universidad de Chile













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