GRASSHOPPER (ORTHOPTERA, ACRIDIDAE) BAIT FEEDING STUDIES USING RUBIDIUM CHLORIDE

Grasshopper populations were treated with bait formulations containing rubidium chloride as part of microbial control and dispersal studies conducted in 1989 and 1990. Bait feeding was compared in grasshoppers collected 4 d after bait application in 1989 and a d after application in 1990. Retention of Rb was studied from additional collections that were made during the 16 d after application in 1990. Rb concentration s in grasshopper tissues mere estimated with atomic absorption spectro photometry: Bait consumption increased with successive instars, but di d not keep pace with increases in body weight. Consumption by adults w as notably less than expected for their size. The migratory grasshoppe r, Melanoplus sanguinipes (F.), and the Packard grasshopper, M. packar dii Scudder, consumed comparable amounts of RbCl for a given instar. A ssimilation rates varied considerable within each stage and species Am ong those grasshoppers that assimilated the most Rb, concentrations de creased the Ist 6 d after application, remained stable during the nest 5 d, and decreased again bu 16 d after application. These results can be used in future studies to optimize bait feeding and dispersal stud ies.