(1687) Redi ( 1626 - 1671 ) established that insects , too , have both sexes ; that they mate and that the females produce fertilized eggs from which the young insects develop ( Esperienze intorno alla generazione degl ' insetti , 1688 ) .Redi also reported that flies are attracted by the smell of decaying flesh ; that ley they eggs on the meat , and that maggots come out of these eggs and develop into flies .However , L .