Aphytis melinus is a parasitoid that was introduced into California in the late 1950’s for control of California red scale (CRS) (Aonidiella aurantii [Maskell]), a serious pest for citrus growers. Since this introduction, A. melinus has been reared in insectaries throughout California and has been a key player in biological control of CRS in southern California. However, the recent heavy usage of several insect growth regulators in the San Joaquin Valley has replaced the augmentative releases of A. melinus. We hypothesize that CRS will develop resistance to these new insecticides and it will then be imperative to have a well-studied, biologically-based management program to turn to. We will be evaluating the fitness of A. melinus reared in 5 insectaries in California using simple life-history trait measurements (sex ratio, size and longevity). The goal of this study is to improve the effective utilization of insectary-reared A. melinus by citrus growers.