A Grid information system should rely upon two basic features: the replication and dissemination of information about Grid services and resources, and an intelligent distribution of such information among Grid hosts. This paper examines an approach based on ant-based systems to replicate and map Grid services information on Grid hosts according to a given semantic classification of such services. Information is disseminated by agents (ants), which traverse the Grid by exploiting the P2P interconnections among Grid hosts. An entropy index is used to evaluate the performance of the proposed Ant-based Replication and MApping protocol (ARMAP), and control the dissemination of resource information. This approach enables the use of a semi-informed search algorithm which can drive query messages towards a cluster of peers having information about resources belonging to the requested class. A simulation analysis has been performed to evaluate the performance of the ARMAP protocol.