Tychius (s. str.) squamulatus Gyllenhal, 1836

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 : 17-18

Tychius (s. str.) squamulatus Gyllenhal, 1836

Clark et al. 1978: 641. Caldara 1990: 166.

Material examined. 20 larvae obtained from pods of Lotus corniculatus L. collected 20.vi.1981 at Bobbio , Piacenza province , Emilia (northern Italy), leg. R. Caldara, and 10 pupae obtained 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. All thoracic and abdominal segments whitish yellow.

HEAD CAPSULE AND MOUTH PARTS. Head width: 0.44–0.55 mm (see Table. 1 ). Endocarinal line present, exceeding middle of frons. Des 1 located almost in central parts of epicarnium; des 2 absent; des 3 located along frontal suture; des 4 absent; des 5 located anterolaterally (Fig. 112). 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. 112). 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 3 very short, triangular, sensilla (Fig. 115).

Labrum (Fig. 116) approximately 2.7 times as wide as long; lms 1 distinctly longer than lms 3, lms 2 slightly shorter than lms 1; anterior margin rounded. Clypeus (Fig. 116) 3.5 times as wide as long; with 2 pairs of very short cls of same length, and 1 sensillum, all located posterolaterally; anterior margin slightly curved inside. Epipharynx (Fig. 117) with 2 pairs of moderately long als, 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. 114): molar edge jagged with triangular tooth; mds 1–2 short, almost of equal length. Maxilla (Fig. 113): stipes with 1 stps, and 2 pfs of equal length; mala with 4 curved dms, different in length; with 2 vms, short and almost of equal length. Maxillary palpi: length ratio of basal and distal palpomeres 1:0.7; basal palpomera with 1 short mpxs; distal palpomera with group of 4 conical, cuticular apical processes. Prementum (Fig. 113) elliptical, with 1 prms; margin of ligula slightly rounded; ligula with 4 lig; premental sclerite distinct. Postmentum (Fig. 113) with 3 pairs of pms, different in length.

THORAX AND ABDOMEN. Body length 2.5–3.1 mm (see Table. 1 ), moderately elongate. Abdominal segment I slightly smaller than others; abdominal segments II–VI almost equal in length; larger than abdominal segments VII–VIII ( Fig. 118 ). Spiracles on abdomen in median parts of segments (abdominal seg. I–VIII).

Chaetotaxy of body reduced. Setae moderately long or short and light yellow. Thorax. Prothorax ( Fig. 119 ) with 8 prn, all macrosetae of different length; 2 moderately long ps of same length; 1 eus. Meso- and metathorax ( Fig. 119 ) with 1 prs; 3 pds, different in length; 1 ss; 1 eps; 1 ps; and 1 short eus. Each pedal area of thoracic segments well-separated and with 2 pda. Abdomen. Abdominal segments I–VII ( Fig. 120 ) with 1 prs; 2 pds of different length; 1 ss; 2 eps of different length; 1 ps; 1 lsts; and 2 eus. Abdominal segment VIII ( Fig. 121 ) with 2 pds of different length; 1 eps; 1 ps; 1 lsts; and 2 short eus. Abdominal segment IX ( Fig. 121 ) with 2 ds of different length; 1 ps; and 2 sts of different length. Each anal lobe on abdominal segment X ( Fig. 121 ) without setae.

Description of pupa. COLORATION. Body whitish yellow.

MORPHOLOGY ( Figs. 122–124 ). Body length 2.5–3.3 mm; widest part 1.2–2.2 mm (see Table. 1 ). Body elongate. Rostrum very long, approximately 7 times as long as wide, reaching mesocoxae. Pronotum 1.8 times as wide as long.

CHAETOTAXY ( Figs. 122–124 ). Setae distinct, moderately long, unequal in length, light brown; on pronotum and head placed on conical protuberances. Head capsule including 1 vs, 2 os of different length; and 1 pas. Rostrum with 1 rs located medially. Vs and os 1 as long as setae on pronotum, distinctly longer than os 2, pas and rs. Pronotum with 2 as, 2 ls, 1 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 1 fes. Setae on abdominal segments I–VIII placed medially and laterally; all abdominal setae located on small, conical protuberances. Pseudocerci conical, short.

Biological observations. Pupae were noted after 8 days from the introduction of larvae into the soil. Adults were observed first in pupal cells after another 12 days. No adult left its cell during the following 30 days, then they were removed artificially.

Remarks. Clark et al. (1978) described two larvae collected by Urban in Germany in fruits of Melilotus alba Medicus and classified by the same collector ( Urban 1935) as T. flavicollis auctorum (non Stephens), currently T. squamulatus , a species which however usually lives on Lotus ( Hoffmann 1954; Caldara 1990). The description by Clark et al. (1978) is very brief and does not correspond to our study in the number of setae on abdominal postdorsum. They reported 3 setae there, but we observed 2 pds and 1 ss (see Material and Methods).

Figures

FIGURES 118–121. Tychius squamulatus mature larva habitus: 118—lateral view, 119—lateral view of thoracic segments, 120—lateral view of abdominal segment I., 121—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 122–124. Tychius squamulatus pupa habitus: 122—ventral view, 123—dorsal view, 124—lateral view (vs—vertical 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).