Tychius (s. str.) alpinus Hustache, 1926

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 : 10-11

Tychius (s. str.) alpinus Hustache, 1926

Caldara 1990: 122; 1995a: 127.

Material examined. 3 larvae from pods of Astragalus monspessulanus L. collected 10.vi.1990 around the artificial Lavagnina lakes, Alessandria province, Piemonte (northern Italy), leg. R. Caldara, and 11 pupae obtained from larvae collected similarly to the others, all determined by association with reared adults.

Differential diagnosis. See Tables 2 and 3 .

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

HEAD CAPSULE AND MOUTH PARTS. Head width: 0.49–0.52 mm (see Table. 1 ). Endocarinal line present, exceeding middle of frons. Des 1 located almost in central parts of epicarnium; des 2 located almost in central parts of epicarnium close to pes; des 3 located along frontal suture; des 4 absent; des 5 located laterally ( Fig. 34 ). Fs 1 and fs 2 absent; fs 3 short, located medially; fs 4 located anteromedially (along epistoma); fs 5 located anterolaterally (along epistoma), 3 to 4 times longer than fs 3 ( Fig. 34 ). Les distinctly shorter than des 3. Ves very short. Postepicranial area with group of 4 minute pes. Antennal segment membranous, bearing conical sensorium and 3 very short, triangular, sensilla ( Fig. 37 ).

Labrum ( Fig. 38 ) approximately 3 times as wide as long; lms 1 2 times longer than lms 3; lms 2 slightly shorter than lms 1; anterior margin slightly sinuate. Clypeus ( Fig. 38 ) 3.5 times as wide as long; with 2 pairs of short cls of same length, and 1 sensillum, all located posterolaterally; anterior margin slightly rounded inside. Epipharynx ( Fig. 39 ) with 2 pairs of als, different in length; with 2 pairs of short ams, ams 1 distinctly shorter than ams 2; with 3 relatively short and finger-like mes; labral rods relatively long, elongate, almost parallel. Mandibles ( Fig. 36 ) with 2 short mds, almost of equal length. Maxilla ( Fig. 35 ): stipes with 1 stps; and with 2 pfs of different length; mala with 5 slightly curved dms, different in length; with 4 vms, moderately long and almost of equal length. Maxillary palpi: length ratio of basal and distal palpomeres 1:1.25, basal palpomera with 1 short mpxs; distal palpomera with group of 3–4 conical, cuticular apical processes. Prementum ( Fig. 35 ) triangular, with 1 prms; margin of ligula slightly rounded; ligula with 1 lig; premental sclerite distinct. Postmentum ( Fig. 35 ) with pms, different in length.

THORAX AND ABDOMEN. Body length 3.1–3.5 mm (see Table. 1 ), elongate. Abdominal segments I–V almost equal in length, slightly larger than abdominal segments (VI), VII ( Fig. 40 ). Spiracles on abdomen in anteromedian parts of segments (abdominal segments I–VIII).

Chaetotaxy of body developed. Setae moderately long or short and light yellow. Thorax. Prothorax ( Fig. 41 ) with 7 prn, 4 macro- and 3 microsetae; 2 moderately long ps of same length; 1 eus. Meso- and metathorax ( Fig. 41 ) with 1 prs; 2 pds, different in length; alar area with 1 very short as; 1 very short ss; 1 eps; 1 ps; and 1 short eus. Each pedal area of thoracic segments well-separated and with 3–5 pda, different in length (long, moderately long, short). Abdomen. Abdominal segments I–VII ( Fig. 42 ) with 1 prs; 2 pds of different length; 2 ss of different length; 2 eps of different length; 2 ps; 1 lsts; and 2 short eus. Abdominal segment VIII ( Fig. 43 ) with 2 pds of different length; 1 ss; 2 eps of different length; 1 ps; 1 lsts; and 2 short eus. Abdominal segment IX ( Fig. 43 ) with 1 ds; 1 ps; and 1 sts. Anal lobes on abdominal segment X ( Fig. 43 ) without setae.

Description of pupa. COLORATION. Body yellow.

MORPHOLOGY ( Figs. 44–46 ). Body length 2.6–3.1 mm; widest part 1.0– 1.5 mm (see Table. 1 ). Body elongate. Rostrum long, approximately 6 times as long as wide, reaching mesocoxae. Pronotum 1.8 times as wide as long.

CHAETOTAXY ( Figs. 44–46 ). Setae distinct, moderately long, unequal in length, light brown; on pronotum and head placed on conical protuberances. Head capsule including 1 vs, 1 os, and 1 pas. Rostrum without setae. Vs and os as long as setae on pronotum, distinctly longer than pas. Pronotum with 2 as, 2 ls, 2 ds, and 1 pls; ds smaller than other setae on pronotum. Dorsal parts of meso- and metathorax with 1 seta. Each apex of femora without seta. 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. 15 % of collected pods were infested by larvae. Also the adults were not numerous on the flowering plants and some of them were collected at the base of the stems. Pupation was observed 10 days after the entrance of the larvae into the soil. Duration of the pupal stage was 10 days. Adults emerged from the pupal cells after a few days.

Remarks. Adults of this species appear closely related to adults of T. brisouti (see below) and both belong to the T. intrusus group which is composed of about 35 species mostly living on Galegeae. However the differences in immatures of these two species are noteworthy (see Table 2 and Discussion). Tychius alpinus is monophagous on Astragalus monspessulanus and with a narrow area of distribution which include southern France, southern Switzerland and north-western Italy. It is considered a rare species and collected in small numbers, usually by netting. However this method is partly unsuccessful due to the fact that the host plant has short and repent stems. Many specimens can be collected by shaking each plant directly into the net or by sifting the soil near the plants.

Figures

FIGURES 34–39. Tychius alpinus mature larva head, antenna and mouth parts: 34—dorsal view (des—dorsal epicranial s., fs—frontal epicranial s., les—lateral epicranial s., pes—posterior epicranial s., st—stemmata, at—antenna); 35—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.); 36—right mandible (mds—mandible dorsal s.); 37—antenna; 38—labrum and clypeus (cls—clypeal s., lms—labral s.); 39—epipharynx (ams—anteromedial s., als—anteriolateral s., mes—median s., lr—labral rods).

FIGURES 40–43. Tychius alpinus mature larva habitus: 40—lateral view, 41—lateral view of thoracic segments, 42—lateral view of abdominal segments I–II., 43—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 44–46. Tychius alpinus pupa habitus: 44—ventral view, 45—dorsal view, 46—lateral view (vs—vertical s., os—orbital s., pas—postantennal s., as—apical s., ls—lateral s., ds—discal s., pls—posterolateral s., pc—pseudocerci).