Tychius (s. str.) meliloti Stephens, 1831

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 : 22-23

Tychius (s. str.) meliloti Stephens, 1831

Clark et al. 1878: 646. Caldara 1990: 179.

Material examined. 18 larvae from pods of Melilotus alba collected 30.vii.1982 at Rozzano , Milano province, Lombardia ( Italy), leg. R. Caldara, and 22 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 brown to dark yellow. All thoracic and abdominal segments light yellow.

HEAD CAPSULE AND MOUTH PARTS. Head width: 0.38–0.42 mm (see Table. 1 ). Endocarinal line absent. Des 1 located almost in central parts of epicarnium; des 2 located very near frontal suture, near des 3; des 4 located anterolaterally; des 5 located laterally; des 2 and des 4 4 times shorter than others (des 1, des 3, des 5) ( Fig. 177 ). 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. 177 ). Les almost as long as 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. 180 )

Labrum ( Fig. 181 ) approximately 3.2 times as wide as long; lms 1 distinctly longer than lms 3, lms 2 of same length as lms 1; anterior margin slightly curved inside. Clypeus ( Fig. 181 ) 3.25 times as wide as long; with 1 short cls located posterolaterally; anterior margin rounded. Epipharynx ( Fig. 182 ) 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 short, kidney-shaped, converging posteriorly. Mandibles ( Fig. 179 ) with 2 short mds, almost of equal length. Maxilla ( Fig. 178 ): stipes with 1 stps, and 2 pfs of equal length; mala with 4 curved dms, different in length; with 3 vms, short and almost of equal length. Maxillary palpi: length ratio of basal and distal palpomeres almost 1:1; basal palpomera with 1 short mpxs; distal palpomera with group of 3–4 conical, cuticular apical processes. Prementum ( Fig. 178 ) trapezoid, with 1 prms; margin of ligula slightly sinuate, ligula with 1 lig; premental sclerite distinct. Postmentum ( Fig. 178 ) with 3 pairs of pms, different in length.

THORAX AND ABDOMEN. Body length 2.1–2.6 mm (see Table. 1 ), elongate. Abdominal segments I–VI almost of equal in length ( Fig. 183 ). Spiracles on abdomen in anteromedian parts of segments (abdominal seg. I–VIII).

Chaetotaxy of body reduced. Setae moderately short or short, and light yellow. Thorax. Prothorax ( Fig. 184 ) with 8 prn; 4 macro- and 4 microsetae; 2 moderately long ps of same length; 1 eus. Meso- and metathorax ( Fig. 184 ) with 1 prs; 2 pds, different in length; alar area with 1 short as; 1 short ss; 1 eps; 1 ps; and 1 short eus. Each pedal area of thoracic segments well-separated and with 3 pda, equal in length (moderately long). Abdomen. Abdominal segments I–VII ( Fig. 185 ) 2 pds of different length; 2 ss; 1 eps; 1 ps; and 2 short eus. Abdominal segment VIII ( Fig. 186 ) 1 pds; 2 ss; 1 eps; 1 ps; and 2 short eus. Abdominal segment IX ( Fig. 186 ) with 1 ds; 1 ps; and 1 sts. Anal lobes on abdominal segment X ( Fig. 186 ) with 1 very short, feebly visible seta.

Description of pupa. COLORATION. Body salmon.

MORPHOLOGY ( Figs. 187–189 ). Body length 1.6–2.2 mm; widest part 0.8–1.1 mm (see Table. 1 ). Body rather stocky. Rostrum very long, approximately 7 times as long as wide, almost reaching metacoxae. Pronotum 1.6 times as wide as long.

CHAETOTAXY ( Figs. 187–189 ). Setae distinct, moderately long, unequal in length, light brown; on pronotum and head placed on small protuberances. Head capsule including 1 vs, 2 os of different length, and 1 pas. Rostrum without setae. Vs and os 1 as long as setae on pronotum, distinctly longer than os 2 and pas. 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 without seta. Setae on abdominal segments I–VIII placed medially and laterally; all abdominal setae located on small, conical protuberances. Pseudocerci conical, short.

Biological observations. Pupation was observed 8 days after the entrance of larvae into the soil. Duration of the pupal stage was 6 days. Adults quickly emerged at the surface 2–3 days later. At the moment of the collection of the mature pods adults were very common and several of them were in copula

Remarks. In the same plants where T. meliloti was collected, there were also many adults of T. breviusculus (see the remarks of this species for further details). Previously there was only incomplete information on immatures of this species. In fact Clark et al. (1978) mentioned that Scherf (1964) provided a brief description of larva without illustration and that this description corresponds with their generic description.

Figures

FIGURES 177–182. Tychius meliloti mature larva head, antenna and mouth parts: 177—dorsal view (des—dorsal epicranial s., fs—frontal epicranial s., les—lateral epicranial s., pes—posterior epicranial s., st—stemmata, at—antenna); 178—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.); 179—right mandible (mds—mandible dorsal s.); 180—antenna; 181—labrum and clypeus (cls—clypeal s., lms—labral s.); 182—epipharynx (ams—anteromedial s., als—anteriolateral s., mes—median s., lr—labral rods).

FIGURES 183–186. Tychius meliloti mature larva habitus: 183—lateral view, 184—lateral view of thoracic segments, 185—lateral view of abdominal segment I., 186—lateral view of abdominal segments VIII–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., eus—eusternal s., ds—dorsal s., sts—sternal s.).

FIGURES 187–189. Tychius meliloti pupa habitus: 187—ventral view, 188—dorsal view, 189—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).