The structure and size of the carbohydrate chain can be very diverse and can alter the physicochemical characteristics of a protein. Two major types of glycosylation, referred to as N- and O-linked glycosylation, can be distinguished. N-glycans are attached to Asn residues of the peptide backbone while O-glycans are connected to Ser or Thr residues. Only in recent years, it has been acknowledged that glycosylation of proteins modulates various processes such as subcellular localization, protein quality control, cell-cell recognition and cell-matrix binding events. In turn, these important functions control developmental processes such as embryogenesis or organogenesis. Although the overall importance of glycosylation is recognized nowadays, the different types of glycosylated proteins in an organism are mostly unknown indicating that the full range of biological and cellular functions is still not fully understood. Deciphering the complexities in biosynthesis and function of glycoproteins in multicellular organisms is a major challenge for the coming decade. Insects are without any doubt the largest animal taxon found on Earth accounting for more than half of all known living species. Their unprecedented evolutionary success is the result of an enormous genetic and phenotypic diversification allowing insect species to adapt to a wide variety of ecological niches and environmental challenges. For example, the genetic diversity within one insect order is already much wider than between distant vertebrates such as human and zebrafish, spanning a whole phylum. Because insects are the most diverse organisms in the history of life, they should provide profound insights into diversification of glycobiology in general and differences of glycosylation in particular. To date, almost all information concerning glycobiology in insects was obtained from studies with the fruit fly, Drosophila melanogaster, the best studied insect laboratory model organism. For D. melanogaster, different glycosyltransferases and glycosylhydrolases which are responsible for synthesis and trimming of N-glycans have been reported suggesting the presence of multiple glycan structures on glycoproteins. Moreover, at least 42 discrete N-glycans have been identified recently in D. melanogaster, mostly containing oligomannose and core fucosylated paucimannosidic N-glycans. Considering the broad diversity among insect species, it can be expected that the diversification in glycan patterns will even be more extensive when analyzing glycosylation patterns in different insect species. In this study, the functional diversity of glycoproteins was studied for insect species belonging to five important insect orders. We SCH772984 selected four insects with a complete metamorphosis, the flour beetle Tribolium castaneum, the silkworm Bombyx mori, the honeybee Apis mellifera and the fruit fly D. melanogaster, as well as one insect species with an incomplete metamorphosis.