-The exoskeleton (cuticle) of insects varies widely in shape, biomechanical properties, and functions, which are inherent to the biological species and developmental stage, besides showing a wealth of architectural specializations and nuances in the different body regions. The morphological pattern of exoskeleton maturation was studied in eusocial and solitary bees, including species of all three eusocial tribes of corbiculate bees as follows: Apini, Meliponini, and Bombini. The results showed striking differences in the rate of cuticle maturation between the solitary bees that leave the nest soon after the adult ecdysis, and the eusocial bees that take longer to leave the colony for foraging activities. There was a clear delay in the postecdysial cuticle tanning (melanization and sclerotization) in the eusocial bee species in comparison to the solitary species, suggesting adaptation to sociality and to the protective environment of the colony. Such heterochrony of cuticle maturation seems a conserved ontogenetic trait related to the way of life in corbiculate bees. The data generated a basic framework of exoskeleton maturation in corbiculate bees, under ontogenetic and evolutionary approaches, and give experimental support for further research on adaptation to the colony environment.exoskeleton / tanning / eusociality / Apinae / solitary bees

Ninety per cent of the species known have solitary behaviour and diversified nesting habits (O'Neill, 2001). The female captures several insects or spiders to provision the cells, exerting a very significant predation pressure on ecosystems (Krombein, 1967). Around 5% of all species of solitary wasps have the habit of nesting in pre-existing cavities (Krombein, 1967). This characteristic has facilitated the study of these solitary species, because females are attracted to nest in human-made trap-nests. In studies made with solitary wasp species that nest

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