Details of a method originated by A.C. Neville for aging adult insects by counting daily growth rings in tibial or other body sections are given. A test of the method’s accuracy using laboratory-reared field crickets (Gryllus pennsylvanicus and Gryllus veletis) showed that the number of growth rings counted is equivalent to the number of days past adult molt until the insect is approximately 25-30 days old, when cuticle growth is completed and rings are no longer added. Field populations of the two cricket species sampled in 2 years seldom contained individuals with more than 18 rings. Several applications for the technique to ecological and behavioral studies are given, using examples from data on G. veletis and G. pennsylvanicus.