Due　to　the　limited　energy　of　wireless　sensor　nodes,　the　energy　efficiency　of　data　collection　is　a　key　issue　in　wireless　sensor　network　(WSN).　Dynamic　clustering　is　a　scalable　and　energy　efficient　solution　for　data　collection　in　WSN.　However,　it　suffers　from　the　imbalanced　energy　consumption　in　the　intercluster　communication.　To　solve　this　problem,　in　this　paper,　we　propose　a　distributed　and　adaptive　routing　protocol　for　cluster-based　wireless　sensor　networks　(DARC).　In　DARC,　an　adaptive　energy　threshold　is　proposed　for　the　cluster　head　to　control　its　intercluster　routing　mode,　and　a　tunable　cost　function　is　designed　for　relay　selection.　Simulation　results　prove　that　DARC　effectively　balances　the　energy　consumption　in　the　intercluster　communication　and　hence　improves　the　energy　efficiency　and　prolongs　the　network　lifetime.　©　2015　Zhezhuang　Xu　et　al.