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In delay-tolerant networks (DTNs), information search is a significant topic that has yet to be widely investigated. Although social-based approaches can be used to address the problem, most existing schemes employ the multihop paradigm and leave out the severe resource constraint in DTNs. In this paper, we experimentally explore several realistic data sets and then reveal that users' one-hop neighbors can cover most range of the whole network in a reasonable time period, which lays a solid fundamental for two-hop information search schemes. Therefore, we propose DelQue (delegation query), which is a novel two-hop delegation query scheme integratedly considering query and response to save network energy in terms of the number of involved relays. In DelQue, we exploit the social utility of each neighbor to represent its capability to query interesting information and then colocate with the source to respond. Furthermore, we also present a spatio-temporal prediction method of user mobility to compute neighbors' utility. Such a lightweight forecasting technique only requires network users to maintain two parameters, making it suitable for a resource-scarce mobile setting. Extensive realistic trace-driven simulations show that DelQue allows for the maintenance of a very high and steady information query ratio with extremely low energy cost and, meanwhile, achieves comparable or shorter delays compared with some existing schemes.