In this paper, we present an adaptive and scalable Web search system, based on a multi-agent reactive architecture, which drew inspiration from biological researches on the ant foraging behavior. Its target is to search autonomously information on particular topics, in huge hypertextual collections, such as the Web, exploiting the outstanding properties of the agent architectures. The algorithm has proven to be robust against environmental alterations and adaptive to user's information need changes, discovering valuable evaluation results from standard Web collections