Tychius amplicollis Aube 1850

Tychius amplicollis Aubé, 1850 Material examined. Mature larvae: 10 exx., pupae: 4 ♂♂ and 4 ♀♀, adults: 30 exx. from: Italy, Latium (Rome province) road Civitavecchia – Allumiere, via Terme di Traiano 329 m, 42°6.855'N, 11°51.688'E, on 16. V. 2018, leg. R. Casalini & E. Colonnelli; same locality 02. VI. 2018, leg. R. Casalini & E. Colonnelli; same locality 16. V. 2020, leg. R. Casalini; same locality 20. V. 2024, leg. R. Casalini. On Vicia macrocarpa. All specimens were identified by association with adults collected on the same plant. Description of mature larva. Measurements (in mm): body length: 4.70–5.80 (mean 5.20); body width: 1.7–2.2 (mean 2.0) (at the level of metathorax); head width: 0.975 –1.750 (mean 1.040). Colouration. Live larva yellow, with dark yellow head capsule; pronotal shield slightly more sclerotised on the anteromedial part (light brown) (Fig. 1 A). General. Body moderately stout, slightly curved, rounded in cross section. Prothorax prominent; pronotum weakly separated. Mesothorax slightly narrower than metathorax, together wider than prothorax. Meso- and metathorax each divided dorsally into two lobes (prodorsal lobe slightly wider than postdorsal). Pedal lobes of thoracic segments weakly isolated. Abdominal segment I as large as metathorax. Abd. segments II – V of similar size, wider than abdominal segment I; segments VI and VII wide; segment IX much smaller than previous one; segment X reduced, divided into three lobes (dorsal the biggest, two lateral slightly smaller, almost of equal size). Abdominal segments I – VII divided into three dorsal lobes of unequal size: prodorsal and postdorsal folds prominent, of similar size, middle fold narrow); abd. segment VIII dorsally partially divided, both folds similar in size; segment IX dorsally undivided. Epipleural and pleural lobes of abd. segments I – VIII conical, well isolated. Abd. segment IX reduced, divided into lateral, pleural and sternal lobes. Anus terminal (Fig. 1 A). Thoracic spiracle bicameral (Fig. 1 B) laterally placed close to border with mesothorax, abdominal spiracles unicameral (Fig. 1 C) medio-laterally placed on segments I – VIII. Cuticle of body smooth. Vestiture. Setae various in length, hair-like, moderately elongate or short, transparent. Thorax (Fig. 1 D): prothorax with 6 prns all medium length, equal in size, 2 medium ps and 1 minute eus. Meso- and metathorax each with 1 short prs and 3 various in length pds, 1 medium eps, 1 medium ps and 1 minute eus. Pedal areas of thoracic segments each with 3 pda of various length (2 medium and 1 short). Abdomen (Fig. 1 E, F): segments I – VIII with 2 short prs, 3 various in length pds, 1 short and 1 medium ss (segment VIII with 1 medium ss only), 1 medium eps, 2 various in length ps (1 minute and 1 medium), 1 minute lsts and 2 minute eus. Abdominal segment IX with 2 medium, equal in length ds, 1 minute ps and 2 minute sts (Fig. 1 F). Each lateral lobe of abdominal segment X with single, minute ts. Head capsule (Fig. 2 A, B) slightly bilaterally narrowed; endocarina elongate, reaches 1 / 2 of frons; frontal sutures distinct along entire length up to antennae; 2 stemmata (st) visible, first placed at the end of frontal suture, second lateromedially. Setae of head medium to short, hair-like, transparent. Cranial setae: medium des 1 placed medially, des 2 minute placed close to des 3, medium des 3 placed at lateral margin of frontal suture, des 4 minute, medium des 5 placed anterolaterally; fs 1 and fs 2 absent, short fs 3 placed anteromedially, medium fs 4 placed anteromedially, and medium fs 5 placed anterolaterally; medium les 1 placed postero-laterally, les 2 absent, and 2 short ves, postepicranial area with 2 minute pes. Antennae (Fig. 3 A, B) placed on each side at anterior margin of head, close to internal border of frontal suture; membranous basal segment convex, semispherical, bearing conical, short sensorium and 5 sensilla basiconica (sb), 1 in middle and 4 on anterior side of basal segment. Clypeus (Fig. 4 A, B left side) trapezoidal, approximately 3.5 times longer than wide, with 2 very short, medially placed cls and single sensillum (clss) placed anteriorly between cls. Anterior margin of clypeus slightly sinuate. Mouthparts. Labrum (Fig. 4 A, B left side) approximately 2 times longer than wide, anterior margin distinctly sinuate; lrs 1 rather short, medially placed; both lrs 2 and lrs 3 medium, anterolaterally placed. Epipharynx (Fig. 4 A, B right side) with 3 als and 2 ams, all elongate, 3 medium, slightly curved mes, equal in size. Labral rods (lr) nearly kidney-shaped, slightly posteriorly converging. Mandible (Fig. 5 A – C) rather narrow, bifid, apical tooth much higher than internal one. Cutting edge strongly serrated, without additional protuberance. Setae: mds 1 and mds 2 minute, hair-like, both lateromedially placed. Maxillolabial complex (Fig. 6 A – C) moderately wide, on stipes with 1 elongate stps, and 2 elongate pfs. Mala with 4 dms, various in size (1 st, 2 nd and 4 th elongate, 3 rd short) (Fig. 6 B) and a group of 3 various in size vms (1 st and 2 nd sharp, medium, 3 rd digitate, small), and 1 minute malar basiventral sensillum (mbs) (Fig. 6 C). Maxillary palpi with 2 palpomeres; basal palpomere distinctly wider and 1.5 times longer than distal one. Basal palpomere with 1 short mps and 1 pore. Distal palpomere with a group of 4 apical sensilla on terminal receptive area (tra). Surface of mala smooth. Labium with subtriangular prementum, with 1 medium prms placed medially. Ligula concave, with 1 minute ligs. Premental sclerite nearly ring shaped; postmentum wide, membranous with 3 pms: elongate pms 1 situated postero-medially, medium pms 2 placed laterally and short pms 3 placed antero-laterally. Labial palpi 1 - segmented. Each palpus with single pore, and a group of 4 apical sensilla on terminal receptive area. Surface of labium smooth. Description of pupa. Measurements (in mm): body length: 4.20–3.60 (mean 2.60); body width: 2.20–3.00 (mean 2.60); thorax width: 1.30–2.00 (mean 1.50); rostrum length: 1.00–1.50 (mean 1.30). Colouration and morphology. Body yellow, rather stout; cuticle smooth (Fig. 7 A – C). Rostrum very elongate, 7.5 times as long as wide in both ♂ and ♀, exceeding metacoxae. Pronotum 1.5 times wider than long, rounded laterally, strongly narrowed apically (Fig. 7 A – C). Mesonotum half as long as metanotum. Abdominal segments I – V of equal length, segments VI and VII tapering gradually, segment VIII semicircular, segment VIII narrow, segment IX terminal, with urogomphi (ur) laterally situated, slightly recurved, short, each with sclerotized, sharp apex (Fig. 7 A, B). Spiracles placed dorso-laterally on abdominal segments I – VI, functional on segments I – V, vestigial on segment VI. Chaetotaxy (setal numbers given for 1 side of the body): setae variable in size, hair-like. Rostrum with 1 medium pas. Head with 1 medium os, 1 short sos and 1 medium vs (Fig. 7 D, F). Pronotum with 2 as, 2 ls, 2 ds and 1 pls. All pronotal setae medium. Meso- and metathorax with 1 short seta (d 1) placed medially on dorsum (Fig. 7 E, F). Abdominal segments I – VIII each, with 1 medium seta (d 1) placed anteromedially (Fig. 7 E, F). All abdominal setae placed on protuberances. Segment IX and urogomphi without setae. Lateral parts of abdominal segments I – VIII with 1 medium seta (l 1) placed medio-laterally single minute setae. Ventral parts of abdominal segments without setae. Each femur with 2 short, hair-like setae (fes). Biological observations The species was collected on Vicia macrocarpa (Fabaceae), where the females deposit their eggs within the pods. Larval development occurs inside the seeds. When fully grown, the larvae create a small exit hole in the pod and drop in the ground where they construct a pupal cell using sand grains. Pupation was observed approximately two weeks after the introduction of the larvae into the soil. Vicia macrocarpa is a Mediterranean – Turanian member of the Fabaceae (Kupicha 1981), historically cultivated as forage and consequently considered adventive in Italy, where it is sporadically distributed in all peninsular regions as well as in Piedmont and Liguria (Pignatti 1982; Nimis et al. 2018). Phylogenetic reconstruction Maximum-likelihood analyses based on the COI fragment provided strong support for the monophyly of the genera Sibinia and Tychius as sampled in this study (Fig. 8 A). Tychius amplicollis and Tychius quinquepunctatus (Fig. 8 A, B) were recovered as sister species with strong support and nested well within the genus Tychius, but with weak support. Most deeper relationships within this genus were poorly supported. Just a few years after the description of Apeltarius based on a single taxon – A. multilineatus (currently Tychius) – Tychius amplicollis was placed in the same genus by Bedel (1885), due to the very strict similarities of the adults of these two species differing from each other mainly in the shape of the pronotum, which is more strongly constricted at its apex in T. amplicollis (Caldara 1978). Whereas T. multilineatus is known only from Algeria and doubtfully from Sicily (Baviera and Caldara 2020), T. amplicollis has a larger distribution being known from the central part of North Africa, Italy (mainly Sicily and Sardinia, and rare in a few central and southern regions), and doubtfully from Corsica (Caldara 1978; Alonso-Zarazaga et al. 2023).