This paper addresses the issue of improving multicast packet delivery in mobile ad hoc networks and proposes an adaptive mechanism called Protocol-Independent Packet Delivery Improvement Service (PIDIS) to recover lost multicast packets. PIDIS provides its packet-delivery improvement services to any multicast routing protocol for mobile ad hoc networks by exploiting the mechanism of swarm intelligence to make intelligent decisions about where to fetch the lost multicast packets from. PIDIS is a gossip protocol, and nodes using PIDIS are only concerned with which neighbor nodes to gossip with to recover the most lost packets, rather than which member nodes to gossip with. Thus, it does not rely on membership information in a multicast scenario, which is often difficult to get. PIDIS employs the beneficial aspects of probabilistic routing and adapts well to mobility. PIDIS achieves probabilistic improvement in multicast packet delivery and, unlike other gossip-based schemes, does not need to maintain information about group members from which lost multicast packets are retrieved. Further, the operations of PIDIS do not rely on any underlying routing protocol or primitive, and can be incorporated into any ad hoc multicast routing protocol. We incorporated PIDIS over ODMRP [On-Demand Multicast Routing Protocol in Multihop Wireless Mobile Networks, Kluwer Mobile Networks and Applications, 2000], and compared it against Anonymous Gossip (AG) [International Conference on Distributed Computing Systems (ICDCS 2001) Phoenix, Arizona, April 2001] implemented over ODMRP, and ODMRP itself. Our simulation results show that ODMRP + PIDIS is more efficient and performs better than ODMRP + AG and ODMRP in terms of multicast packet delivery, end-to-end delay, and MAC layer overheads. We attribute the better performance and lower MAC overheads of ODMRP + PIDIS to the efficient gossiping made possible by using the swarm intelligence techniques.