We have played a leading role in the Heliconius Genome Consortium, which has generated a reference sequence for Heliconius melpomene. This has opened exciting opportunities to explore the adaptive radiation in these butterflies at a genomic level. Among 12,657 predicted genes for Heliconius, biologically important expansions of families of chemosensory and Hox genes are particularly noteworthy. The diversity of chemosensory proteins in butterfly genomes was particularly surprising given the evolution of diurnal behaviour and greater visual acuity. The chromosomal organization of Lepidoptera has remained broadly conserved since the Cretaceous period, when butterflies split from the Bombyx (silkmoth) lineage. Using genomic resequencing, we are now exploring patterns of gene flow and divergence during speciation in the genus. In particular we have shown that hybrid exchange of genes between three co-mimics, Heliconius melpomene, Heliconius timareta and Heliconius elevatus, has occurred at two genomic regions that control mimicry pattern.