Research on Chrysomelidae, Volume 2, pp. 15–30, © Koninklijke Brill, Leiden, 2009 Constraints on larval feeding morphology and selective removal of host-plant trichomes by a monophagous cassidine beetle Plate 1 Danessa S. Boligon 1 , Lenice Medeiros 2 , Rosy M. S. Isaias 3 and Gilson R. P. Moreira 4 Abstract. e gross morphology of the alimentary canal of Gratiana spadicea (Klug) (Cassidinae) larva is described, measured, and related to feeding behavior, in par- ticular to the removal and ingestion of four types of trichomes of Solanum sisym- briifolium Lamarck (Solanaceae). e gut is constrained by the ingestion of entire stellate trichomes, because its lumen width is smaller than their radial length. ese trichomes are therefore selectively removed prior to feeding. eir fragments when ingested are packed by the peritrophic membrane (PM) that is produced in the poste- rior portion of the midgut and shed with the feces. us, the PM protects the gut wall from abrasion caused by the pointed apical cells of the trichomes, which protrude into the ectoperitrophic space. e effects of morphometric constraints are more in- tense in the early instars, and are progressively attenuated by an exponential growth in gut width during the larval ontogeny of G. spadicea. Keywords. Chrysomelidae, Solanaceae, Gratiana spadicea, Solanum sisymbriifolium, insect morphology, larval feeding behavior, plant physical defenses 1. Introduction Depending on their density, size, shape, and chemical composition, plant trichomes may hamper movement, access to food, and even digestion by herbivorous insects 1 Departamento de Zoologia, IB, UFRGS, Av. Bento Gonçalves, 9500, Bairro Agronomia, Porto Alegre, RS 91501-970, Brazil 2 DeBQ, UNIJUI, Rua do Comércio, 3000, Ijuí, RS 98700-000, Brazil 3 Departamento de Botânica, ICB, UFMG, Av. Antônio Carlos, 6627, Bairro Pampulha, Belo Horizonte, MG 31270-910, Brazil 4 Corresponding author: Departamento de Zoologia, IB, UFRGS, Av. Bento Gonçalves, 9500, Bairro Agronomia, Porto Alegre, RS 91501-970, Brazil. gilson.moreira@ufrgs.br