We thank Mr Kaoru Nakamura, Mr Toshihiko Misawa and Mr Koji Hashimoto for rearing the silkworms. We thank Ms Sayaka Kobayashi‐Nabana, Ms Satoko Kawamoto, the laboratory technicians and part‐time assistants for their assistance with stock maintenance. We thank Dr Natuo Kômoto for providing B. mandarina, and Professor Yutaka Banno, Dr Hiroshi Fujii and the ‘Silkworm’ National Bio‐Resource Project for providing the chocolate (Δyellow) strain k12. We thank Dr Noriko Funayama for the equipment she provided for use in the Drosophila experiment. We thank Dr Takuya Tsubota, Dr Megumi Sumitani and Dr Shuichiro Tomita for their invaluable comments on this manuscript. This work was supported by a Grant‐in‐Aid for Young Scientists (B), Japan (MEXT/JSPS KAKENHI, Grant No. 16 K21612).