Vertebrate　testosterone,　an　androgen　present　in　the　testes,　is　essential　for　male　fertility.　Vertebrate-type　steroid　hormones　have　been　identified　in　insects,　but　their　function　remains　unknown.　Insect　vitellogenin　(Vg)　is　usually　a　female-specific　protein　involved　in　reproductive　processes.　However,　males　of　some　species,　such　as　the　green　lacewing　Chrysopa　pallens,　have　Vg.　Here,　we　demonstrated　that　the　knockdown　of　C.　pallens　male　Vg　by　RNAi　significantly　shortened　the　lifespan　of　males,　suppressed　the　reproduction　of　post-mating　females,　and　strikingly　reduced　the　abundance　of　several　immune-related　compounds,　including　testosterone.　LC-MS/MS　revealed　that　C.　pallens　male　testosterone　had　the　same　structure　and　molecular　mass　as　vertebrate　testosterone.　Topical　testosterone　application　partially　restored　the　lifespan　of　Vg-deficient　males　and　the　reproduction　of　post-mating　females.　These　results　suggest　that　vertebrate-type　testosterone　maintains　male　longevity　and　female　reproduction　under　the　control　of　the　male　Vg　in　C.　pallens.　©　2024