LAUSR

Abstract Generalist herbivores are less susceptible to changes in the plant composition of their habitats than specialists are because generalists can consume a diverse array of plants. However, even generalists exhibit dietary choices, for example because they need to balance their nutritional intake for both growth and reproduction. In this study, we showed that an endangered generalist herbivorous grasshopper (Celes akitanus; Orthoptera: Acrididae) actively chooses which plants to include in its diet. Moreover, we found that grasshopper abundance is correlated with host plant abundance and richness. This grasshopper has been reported to occur mainly in traditionally managed grasslands that harbour more diverse plant species than other, nearby grasslands. To elucidate the links between this grasshopper and plant richness, we surveyed grasshopper abundance in grasslands under traditional and other management practices. Plant DNA barcoding of faecal samples demonstrated that this grasshopper is a generalist herbivore while also showing that it makes active dietary choices. Furthermore, although the grasshopper's host plants occurred in all grasslands, the grasshopper itself was found only in species-rich grasslands. In addition, grasshopper abundance was positively related to the abundance and richness of host plants. Our findings suggest that this endangered herbivore requires a wide array of host plants to maintain its populations.