This paper shows a novel approach for routing datagrams in irregular satellite constellations, called Distributed Ant Routing (DAR). This approach belongs to the class of routing algorithms inspired by the behavior of the ant colonies in locating food and storing food. The definition of the algorithm is followed by a detailed analysis that has led to the tuning of some important parameters, necessary to optimize the achievable performance. The effectiveness of the algorithm is demonstrated by a comparison with the well known Ad-hoc On Demand Distance Vector (AODV) algorithm. Results obtained by a theoretical analysis and a simulation campaign show the DAR allows obtaining some important advantages that makes it a valuable candidate to operate in irregular satellite constellations.