Web service technologies are playing an increasingly important role in service-oriented architecture design and application convergence over Mobile ad hoc networks (MANET). Due to the decentralized administration and dynamic wireless connectivity problems, accomplishing reliable service discovery in MANET faces a large number of challenges. In order to relieve the communication inefficiency among service providers and clients caused mainly by the unpredictable node mobility, this paper proposes a cross-layer service discovery scheme which enables improved network efficiency and reduced resource consumption. Firstly a network-layer based underlay framework is presented. It specifically establishes a reliability-oriented source routing mechanism which is equipped with a novel reliability-maximized path selection metric and a backup path support fast route recovery strategy. The cross-layer design is prudentially realized by piggybacking service discovery procedures on the reliability enhanced underlay routing mechanism. Simulation analysis verifies that the proposed scheme improves service discovery reliability by achieving low rediscovery frequency, and guarantees high network efficiency by providing reduced service discovery delay and control overhead.