Most insects are associated with mutualistic microorganisms that can confer novel traits and thereby play important roles for the ecology and evolution of host organisms. Although many insects ensure that their offspring are endowed with the beneficial symbionts by transmitting them vertically from parent to offspring, others rely on environmental uptake in every generation. How can these insects choose the best cooperative partner from the diversity of environmental microbes? Proposed means of partner choice - signaling and screening (Archetti et al. 2011)typically are chemically-mediated in cross-kingdom mutualisms. While wellstudied in plant-pollinator and some plant-microbe mutualisms, however, the use of chemical signals (e.g., specific odors, surface attractants) or selective environments (e.g., through nutritional constraints or defensive chemicals) to filter potential partners remains largely unexplored in insect-microbe associations, despite the implications for the ecology and evolution of the host organisms. Ideally, individuals identify beneficial partners in advance of any interaction, thus preventing exploitation of the costly cooperative act. Signaling is a wellknown mechanism for partner selection in animal-animal (e.g. ,c leaner fish), animal-plant (e.g., pollinator and seed dispersal mutualisms), as well as plantmicrobe mutualisms (e.g., legumes and rhizobia, plants and mycorrhizal fungi). Signal honesty is required in order to maintain a mutualism, and thus signals most easily evolve if directly linked to partner quality. In insects, specific long-range signaling and short-distance recognition of mutualistic partners by odors or surface chemicals has been implicated in the establishment of symbiosis in several fungusgrowing insects. Some ambrosia beetle species are attracted to their fungal symbionts, suggesting that signaling by specific microbial volatile organic compounds (MVOCs) mediates the initial stages of partner choice (Hulcr et al. 2011). Long-range beetle attraction by general MVOCs (e.g., short-chain alcohols) is long known, but partner recognition is expected to involve specific secondary compounds (e.g., terpenoids) or blends of general MVOCs. However, since ambrosia beetles usually transmit their symbiotic fungus vertically in specialized pouches (mycangia) and inoculate them into new host trees upon colonization, attraction to the symbiont’s volatiles may direct the beetles to suitable environments for fungus growth rather than providing a signal necessary for symbiosis establishment. By contrast, most fungus-growing termites collect their cultivar’sspores de novo from the environment in each generation, highlighting the need for mechanisms to localize and recognize the symbiotic partner. Currently, it is unknown whether recognition occurs through volatile signals or surface compounds produced by the fungal spores. Given thatspores often are rich in defensive secondary metabolites (e.g., terpenoids, mycotoxins), derivatives of these compounds could be involved in partner choice. Similar to ambrosia beetles and despite vertical transmission of their symbionts, leaf-cutter ants of the genus Acromyrmex chemically recognize their native cultivar fungi (see references in Zhang et al. 2007), as well as discriminate between native and non-native