Résumé
Tychius is a speciose and widespread weevil genus, whose phylogenetic relationships are largely unknown. Here we assess the validity of the subgenus Apeltarius using an integrative approach combining larval morphology and molecular data. The mature larva and pupa of Tychius (Apeltarius) amplicollis Aubé, 1850 are described and illustrated in detail for the first time. Comparisons with known immature stages of several species of Tychius s. str. reveal that the larva and pupa of T. amplicollis exhibit all diagnostic features characteristic of the genus Tychius, showing closest affinity to T. (Tychius) quinquepunctatus (Linnaeus, 1758). Phylogenetic analysis of a fragment of the mitochondrial cytochrome c oxidase subunit I gene confirms their close relationship and supports the inclusion of T. amplicollis in the genus Tychius. Newly obtained biological data show that the life history and host-plant associations of T. amplicollis match those of other Tychius species, with Fabeae (Fabaceae) as hosts. Based on this evidence, we propose that Apeltarius be treated as a junior subjective synonym (syn. nov.) of Tychius. Because there are no other subgenera in the genus Tychius we propose the following combinations: Tychius amplicollis Aubé, 1850; Tychius multilineatus (Desbrochers des Loges, 1873); Tychius quinquelineatus Tournier, 1874; Tychius strigulatus (Desbrochers des Loges, 1875).