Responses of three generations of a xylem-feeding insect, Neophilaenus lineatus (Homoptera), to elevated CO2

A population of the xylem-feeding spittlebug, Neophilaenus lineatus, on blo cks of natural vegetation transferred to large hemispherical chambers was s tudied over two generations with continuous exposure to elevated CO2 (600 p pm). The third generation was transferred from the blocks to potted Juncus squarrosus to enable measurements of fecundity. The principal food plant th roughout was Juncus squarrosus. Survival of the nymphs was reduced by more than 20% in elevated CO2 relative to ambient (350 ppm) in both years of the main experiment. Elevated CO2 also delayed development by one or more nymp hal instars in each year. Fecundity was not significantly affected. The C/N ratio of whole Juncus leaves was increased in elevated CO2 and the transpiration rates of the plants were reduced. These changes may have been responsible for the effect of elevated CO2 on spittlebug performance. Howe ver, other factors such as plant architecture and microclimate may also be important.