Permethylated O-glycans released by β-elimination of Aedes, Anopheles (Ag) or Drosophila (Dm) were analysed in positive mode by NSI-MS as sodiated species, except for sulphated species (S) which were detected either in the form [M-H+2Na]+ in positive ion mode (*) or [M-H]− in negative mode as indicated in square brackets. Reduced, but not permethylated, O-glycans of Aedes and Anopheles were independently released by β-elimination and analysed by LC-MS in negative mode either in the form [M-H]− or [M-2H]2− as indicated in brackets. nd, not detected; S, sulphate; PE, phosphoethanolamine.