a, Comparison of chemosensory and detoxification related gene families between the extremely polyphagous pest S. litura and almost monophagous B. mori. Black thick bars denote the largest bitter GR cluster on Chr 12. R represents receptor. b, There is a large expansion of bitter GR genes on S. litura Chr 14. Thirteen bitter GR genes clustered on S. litura Chr 14 were mainly expressed in moth proboscis and larval maxilla, whereas the corresponding BmorGR gene cluster on Chr 10 composed of BmorGR55-57 was expressed in larval chemoreception organs16. c, Expansion of S. litura single-exon bitter GR genes on Chr 25 mainly expressed in moth proboscis. The corresponding BmorGR53, which is also a single-exon gene, was expressed in larval maxilla. d, Heatmap of S. litura GR expression in various tissues by RNA-Seq. L.Ant., larval antenna; L.Epi., larval epipharynx; L.Leg, larval legs; L.Max., larval maxilla; L.Mid., larval midgut; M.Ant., moth antenna; M.Leg, moth legs; M.P.G., moth pheromone glands; M.Pro., moth proboscis. The vertical red two-way arrow indicates the largest bitter GR cluster on Chr 12, which was mainly expressed in larval maxilla. Thick blue bars represent GR gene clusters on Chr 14 and Chr 25, which were mainly expressed in moth proboscis. R denotes receptor.