Volume 9 of Research on Chrysomelidae (RoC9) presents nine articles reporting new results of research on Chrysomelidae sensu lato, i.e., leaf and seed beetles. Four of these papers are extended versions of oral presentations given at the 10th International Symposium on the Chrysomelidae - Platania & Gómez-Zurita, Furth et al., Schmitt et al., and Geiser. This symposium was held on 21 July, 2022 within the 26th International Congress of Entomology in Helsinki (Finland). The other five papers were submitted independently of the symposium. Altogether, these articles treat taxonomy, morphology, reproduction, life history, behaviour, and ecology. They demonstrate the dynamic, diverse, and compelling research being conducted today on leaf beetles. Chi-Feng Lee & Jung-Chan Chen: Demarchus hsui (Coleoptera, Chrysomelidae, Galerucinae, Alticini), a new species from Taiwan, with notes on immatures and biology. Wei-Li Fan et al.: The morphology and spectral characteristics of the compound eye of Agasicles hygrophila (Selman & Vogt, 1971 (Coleoptera, Chrysomelidae, Galerucinae, Alticini). Platania, L. & Gómez-Zurita, J.: Current knowledge on the diversity of Eumolpinae (Coleoptera, Chrysomelidae) in New Caledonia. Furth, D. G., Montagna, M. & Magoga, G.: Rediscovery of a lost semi-aquatic Leaf Bettle in the Hula Valley, Israel (Coleoptera, Chrysomelidae, Donaciinae). Schmitt, M., Neumann, A. & Shou-Wang Lin: Anatomy of male and female genitalia of Acanthoscelides obtectus (Say, 1831) (Coleoptera, Chrysomelidae, Bruchinae) in interaction. Simmrita Chaboo, C., Adam, S., Nishida, K., Schletzbaum, L.: Architecture, construction, retention, and repair of faecal shields in three tribes of tortoise beetles (Coleoptera, Chrysomelidae, Cassidinae: Cassidini, Mesomphaliini, Spilophorini). Yongying Ruan, Konstantinov, A. S., Damaska, A. F., Lihao Zheng, Jun Chen & Ziye Meng: Description of three new species of Benedictus (Coleoptera, Chrysomelidae, Galerucinae, Alticini) from China, with comments on their biology and modified ethanol traps for collecting flea beetles. Geiser, E.: Revision of the Palaearctic species of the genus Plateumaris C. G. Thomson, 1859 (Coleoptera, Chrysomelidae, Donaciinae). Geiser, E. & Geiser, R.: Original descriptions of Palaearctic species of the genus Plateumaris C. G. Thomson, 1859 (Coleoptera, Chrysomelidae, Donaciinae) and their translations. New taxa: Demarchus hsui n. sp., Benedictus fuanensis n. sp., Benedictus quadrimaculatus n. sp.Benedictus wangi n. sp. Sofia. Pensoft. 258 pp., num. color figs, paperback 4
