Opportunistic Carnivory by Romalea microptera (Orthoptera: Acrididae)

Abstract

Abstract Grasshoppers generally are considered to be phytophagous. However, increasing evidence shows that many are better classified as omnivorous. The eastern lubber grasshopper Romalea microptera (Beauvois) (Orthoptera: Acrididae) not only consumes plants, but also dead or wounded arthropods in the field. We tested the potential range of arthropod taxa scavenged by R. microptera by offering fresh-killed carcasses to adult females in the laboratory. We predicted that they would eat all arthropods except those that the grasshopper's mandibles could not cut and chemically defended arthropods. We offered grasshoppers 104 arthropod species and life stages, representing 20 orders in five classes (Arachnida, Chilopoda, Diplopoda, Insecta, and Malacostraca). The grasshoppers completely consumed the entire body of all individuals of 42% of the arthropod species and life stages, and another 32% were highly consumed. Overall, 96% of the arthropod species and life stages, representing 19 of the 20 total orders, were consumed to some extent, suggesting that R. microptera is an opportunistic carnivore. Chemical defense in arthropods did not deter feeding by R. microptera, but the hardness of integument did: harder-bodied Hymenoptera and Coleoptera were consumed less than softer-bodied arthropods. Our results confirm that R. microptera is not strictly phytophagous, but readily eats a wide range of arthropod taxa. Carnivory within phytophagous clades may have important physiological, ecological, and evolutionary consequences.