The morphology of the metendosternite and the anterior abdominal venter in Chrysomelinae (Insecta: Coleoptera: Chrysomelidae)

Abstract

The skeletal parts of the metendosternite and of the anteromedian part of the abdominal venter are studied in 39 species of Chrysomelinae (representing tribes Timarchini and Chrysomelini, and 10 of the 12 subtribes of Chrysomelini) and 4 species from Galerucinae, Criocerinae, and Cassidinae. The morphology of these body parts in Chrysomelinae is compared with other cucujiform beetles based on the literature, with a focus on a tenebrionid. The morphology of the metendosternite evidently includes much homoplasy across Cucujiformia including Chrysomelidae, whereby conclusions on the polarity of characters are very limited. The (fairly poor) phylogenetic evidence from the chrysomeline metendosternite is discussed including reflection of the current classification, of the only large-scale molecular-based phylogenetic study of Chrysomelinae, and of phylogenetic evidence from glands and their secretions. Chrysomelinae consistently have a very short metendosternal stalk, the anterior tendon originates far laterally from the furcal arm, and the anterior lamina is limited to the furcal arm or entirely absent (i.e. always absent in the median part of the metendosternite). These features appear as apomorphic compared to the examined Galerucinae, Criocerinae, and Cassidinae and suggest the exclusion of Galerucinae from Chrysomelinae (contra molecularbased results). Metendosternal characters suggest Phratora to belong to Chrysomelina, and Zygogramma and Cosmogramma to be close to Chrysolinina rather than Doryphorina; both is in accord with results derived from DNA sequences and from gland secretions. The two Chrysomelinae genera with reduced hind wings (Timarcha, Crosita) show simplifications in the metendosternite. It is suggested that somecharacters may depend on the age of the adults, the development of abdominal hemi-sternites I being one such character.