Toward the Quantification of Predation with Predator Gut Immunoassays: A New Approach Integrating Functional Response Behavior

t f m Immunological methods have been widely used to identify key predator species and qualitatively evaluate predation of target prey. However, despite the quantitative nature of many immunoassays, the translation to number of prey attacked has been problematic because of the many factors that confound interpretation of the strength of the immunoassay response. We developed a new predation model that couples the proportion of predators positive for prey remains determined by enzyme-linked immunosorbent assay (ELISA), predator density, and predator functional response to prey density for estimating total prey attacked. We used single cotton plant arenas in the greenhouse to develop functional response models for two generalist predators, Geocoris punctipes (Say) and Orius insidiosus (Say), preying on Pectinophora gossypiella (Saunders) ggs. The model was validated and compared with ther immunologically based predation models in ultiple plant/multiple predator arenas. Our predaion model was relatively accurate in predicting the otal number of prey attacked by both predator speies and was a significant improvement over previus models that rely on simple assumptions regardng predator attack rates. The model also improves he predictive capacity of the functional response odel alone by correcting for the number of predaors actually consuming prey. Sensitivity analyses ndicated that model performance was most sensiive to accurate measurement of input variables uch as temperature and the proportion of individals positive for prey antigens by ELISA and less ensitive to changes in estimates of prey density. ccurate estimation of the functional response paameters is also important, especially for the behavoral parameter defining the decline in plant leaf rea searched with increases in prey density. Limi-