We characterized evolutionary patterns of host plant use across about 2500 species of British Lepidoptera, using character optimization and independent phylogenetic contrasts among 95 operational taxa, and evaluated the extent to which caterpillars are monophagous, use woody host plants, and feed concealed. We also analyzed the use of different Angiosperm superorders and related these associations to other key variables. The Nepticulidae, Pterophoridae, and Gracillariidae allowed explicit comparisons between the British fauna and the Lepidoptera worldwide, which indicated that our broad categorizations for Britain are accurate predictors for the global fauna. The first (lower glossatan) radiation of the Lepidoptera started with monophagous, internal feeding on woody Eurosids I. Polyphagy on nonwoody Eurosids I evolved together with the ability to feed externally, but did initially not produce significant radiations. Exposed feeding became associated with radiations in the lower Ditrysia and Apoditrysia and remained correlated with more polyphagy, fewer woody host plants, and increasing use of other Angiosperm superorders. The macrolepidopteran radiation has frequent reversals to monophagy on woody Eurosids I, particularly in taxa that lost concealed feeding. We discuss the general implications of these results and address several key adaptations and constraints that have characterized the major transitions in lepidopteran life histories.