Tychius (s. str.) quinquepunctatus (Linnaeus, 1758)

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 : 9-10

Tychius (s. str.) quinquepunctatus (Linnaeus, 1758)

Clark & Burke 1977: 113. Clark et al. 1978: 640. Caldara 1990: 97.

Material examined. 42 larvae from pods of Lathyrus latifolius L. collected 1.vii.1979 at Recco , Genova province, Liguria (northern Italy), leg. R. Caldara, and 24 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 dark brown. All thoracic and abdominal segments salmon.

HEAD CAPSULE AND MOUTH PARTS. Head width: 0.73–0.81 mm (see Table. 1 ). Endocarinal line present, reaching middle of frons. Des 1 located almost in central parts of epicarnium; des 2 located very near frontal suture, near des 3; des 4 located along frontal suture; des 5 located anterolaterally; des 2 and des 4 4 times shorter than others (des 1, des 3, des 5) ( Fig. 21 ). Fs 1 and fs 2 absent; fs 3 short, located medially; fs 4 located anteromedially (along epistoma); fs 5 located anterolaterally (along epistoma), 4 times longer than fs 3 ( Fig. 21 ). Les almost equal in length as des 3. Ves short. Antennal segment membranous, bearing conical sensorium and 2 very short, conical, sensilla ( Fig. 24 ).

Labrum ( Fig. 25 ) approximately 2.6 times as wide as long; lms 1 3 times longer than lms 3, lms 2 slightly shorter than lms1; anterior margin doubly sinuate. Clypeus ( Fig. 25 ) 2.7 times as wide as long; with 2 pairs of very short cls of same length, and 1 sensillum, all located posterolaterally; anterior margin slightly rounded inside. Epipharynx ( Fig. 26 ) with 2 pairs of als, almost of equal length; with 2 pairs of short ams, ams 2 distinctly shorter than ams 1; with 2 long, finger-like and 1 short mes; labral rods relatively long, elongate, strongly converging posteriorly. Mandibles ( Fig. 23 ) with 2 short mds, different in length. Maxilla ( Fig. 22 ): stipes with 1 stps, and with 2 pfs of equal length; mala with 4 straight dms, different in length; with 3 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 4 conical, cuticular apical processes. Prementum ( Fig. 22 ) heart-shaped, with 1 long prms; margin of ligula slightly sinuate; ligula with 1 lig; premental sclerite distinct. Postmentum ( Fig. 22 ) with 3 pairs of pms, different in length.

THORAX AND ABDOMEN. Body length 4.6–7.2 mm (see Table. 1 ), stocky ( Fig. 27 ). Spiracles on abdomen in median parts of segments (abdominal seg. I–VIII).

Chaetotaxy of body strongly reduced. Setae very short, feebly visible, light yellow. Thorax. Prothorax ( Fig. 28 ) with 6 prn, all macrosetae of equal length; 2 moderately long ps of same length; 1 eus. Meso- and metathorax ( Fig. 28 ) with 1 prs; 3 pds; 1 eps; 1 ps almost of same length; 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. 29 ) with 2 prs different in length; 3 pds different in length; 2 ss different in length; 1 eps; 2 ps different in length; 1 lsts; and 2 eus. Abdominal segment VIII ( Fig. 30 ) with 2 prs of different length; 3 pds; 1 ss; 1 eps; 1 ps; 1 lsts; and 2 short eus. Abdominal segment IX ( Fig. 30 ) with 2 ds of different length; and 2 sts of different length. Anal lobes on abdominal segment X ( Fig. 30 ) with 1 very short, feebly visible seta.

Description of pupa. COLORATION. Body salmon.

MORPHOLOGY ( Figs. 31–33 ). Body length 3.1–4.1 mm; widest part 1.9–2.4 mm (see Table. 1 ). Body rather stocky. Rostrum moderately long, approximately 4 times as long as wide, reaching mesocoxae. Pronotum 1.7 times as wide as long.

CHAETOTAXY ( Figs. 31–33 ). Setae distinct, short, unequal in length, light brown; on pronotum and head placed on small protuberances. Head capsule including 1 vs, 1 sos, 1 os and 1 pas. Rostrum with 1 rs located medially. Setae on head slightly shorter than setae on thoracic and abdominal segments. 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 posteromedially and posterolaterally; all abdominal setae located on thorn-like protuberances. Pseudocerci short, slightly curved inside.

Biological observations. Several living larvae, as many as 10 at all stages, were found in a single pod, which however did not show external modifications. Pupation was observed 20 days after the introduction of the larvae in the soil. Adults emerged from the cells 20 days later.

Remarks. This common species with a wide Euro-Asiatic distribution was reported to live on several species belonging to the genera Lathyrus , Phaseolus , Pisum and Vicia ( Hoffmann 1954; Scherf 1964; Caldara 1990), which produce large pods. Larva and pupa were described synthetically by Scherf (1964), whereas Clark et al. (1978) redescribed the larva in more details. The description by Clark et al. (1978) does not correspond partly to our study; (1) head width: 1.23–1.30 mm vs. 0.73–0.81 mm in our study; (2) pronotum with 5 long setae, 2 shorter setae and 1 microseta, whereas we observed only 6 long setae.

Figures

FIGURES 21–26. Tychius quinquepunctatus mature larva head, antenna and mouth parts: 21—dorsal view (des—dorsal epicranial s., fs—frontal epicranial s., les—lateral epicranial s., ves—ventral epicranial s., st—stemmata, at—antenna); 22—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.); 23—right mandible (mds—mandible dorsal s.); 24—antenna; 25—labrum and clypeus (cls—clypeal s., lms—labral s.); 26—epipharynx (ams—anteromedial s., als—anteriolateral s., mes—median s., lr—labral rods).

FIGURES 27–30. Tychius quinquepunctatus mature larva habitus: 27—lateral view, 28—lateral view of thoracic segments, 29—lateral view of abdominal segment I., 30—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 31–33. Tychius quinquepunctatus pupa habitus: 31—ventral view, 32—dorsal view, 33—lateral view (vs—vertical s., sos—super orbital 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).