This invention relates, e.g., to transgenic insects, or progeny thereof, whose cells contain at least one genomically integrated, expressible, nucleic acid encoding two or more of a set of Nglycosylation enzymes that can glycosylate a heterologous protein with a mammalianized (e.g., humanized) glycosylation pattern. The glycosylation genes are preferably expressed in the insect cells in catalytic amounts. Also described are methods to use such a transgenic insect to produce heterologous, mammalianized polypeptides of interest.