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　.