Abstract
Immatures of Mesomphalia gibbosa (Fabricius, 1781) and Mesomphalia turrita (Illiger, 1801) (Coleoptera, Chrysomelidae, Cassidinae, Mesomphaliini) are described based on specimen collections from Rio de Janeiro state, Brazil. The last-instar larva and pupal exuviae of M. gibbosa (Fabricius, 1781) and the eggs, first-instar larva, and pupa of M. turrita (Illiger, 1801) are described, photographed and illustrated, with emphasis on chaetotaxy. Additional notes on their biology are presented.