DIFFERENTIAL UTILIZATION OF NUTRIENTS DURING DEVELOPMENT BY THE XYLOPHAGOUS LEAFHOPPER, HOMALODISCA-COAGULATA

Utilization of nutrients at different stages of development was examin ed for the xylophage, Homalodisca coagulata (Say). Survivorship and co nsumption rates of second-instar, fourth-instar and adult leafhoppers were measured daily on the hosts Lagerstroemia indica L. and Euonymus japonica Thumb. Rates of consumption, assimilation efficiencies and da ily assimilation of nitrogen, carbon, and individual organic compounds were calculated based on chemical analyses of xylem fluid and insect excreta. Gross growth efficiencies of diet utilization were also estim ated by comparing biomass of young adults to estimates of nutrient uti lization of the two host species. Different instars survived and utili zed nutrients at varying rates on the two hosts. Second-instar leafhop pers survived at higher rates and utilized nitrogen more efficiently o n E. japonica than on L. indica. However, assimilated nitrogen was muc h less as a result of lower consumption rates. In contrast, adults on L. indica had increased longevity, utilized carbon more efficiently, a nd assimilated higher quantities of both carbon and nitrogen than thos e on E. japonica. Efficiencies of nutrient utilization were high for H . coagulata compared to folivores or phloem feeders, particularly in t he conversion of ingested nutrients to assimilated compounds. Variatio ns in diet utilization during development are discussed in terms of po lyphagy.