Heteropterans often are the numerically dominant species in the predator complexes of many agricultural systems, yet we have only a rudimentary knowledge of how they function in pest control. Our inability to predict the effect of these and other arthropod predators on pest population dynamics remains the most significant barrier to using predators as components of pest management systems. This problem stems in large part from the difficulty of measuring the activity of predators under field conditions. We briefly examine techniques for studying predation and evaluate them relative to measuring predation quantitatively. We then detail serological techniques, discuss their strengths and weaknesses, and exemplify use of a serological approach for studying the effect of heteropteran predation in the cotton ecosystem. Serology has a long history in the study of insect predation and it is one of the few methods that requires only minimal disruption of the system under examination. We used monoclonal antibodies developed to recognize egg antigens of pink bollworm, Pectinophora gossypiella (Saunders), and sweetpotato whitefly, Bemisia tabaci (Gennadius) strain B (= B. argentifolii Bellows and Perring), to study the native predators of these pests in cotton. Using a multiple-gut ELISA (enzyme-linked immunosorbent assay) we tested more than 22,000 individuals of 7 species of predaceous Heteroptera over 2 field seasons in central Arizona. Based on the frequency of positive ELISA responses and population densities, Orius tristicolor (White) and Lygus hesperus Knight, a recognized pest species, were found to be the dominant predators of pink bollworm and sweetpotato whitefly eggs. Geocoris pallens (Stål), G. punctipes (Say), Nabis alternates Parshley, Sinea confusa Caudell, and Zelus renardii Kolenati appear to be minor predators of eggs of these pests. We propose a new predation model that integrates the results of ELISA, predator population densities, and functional response behaviors. Preliminary analysis of pink bollworm egg predation suggests that the heteropteran predator complex was responsible for removing ≈20% of all pink bollworm eggs over the entire season. This effect was achieved at extremely low (and atypical) densities of this pest.