To test whether the universal food immunomarking technique could be applied in a feeding-choice experiment, researchers placed western tarnished plant bug (Lygus hesperus) eggs in two different setups, one exposed on the surface of an artificial stem and one concealed beneath a thin film to mimic the bug’s egg-laying behavior (beneath the surface of plant tissue). The eggs in each exposure were marked with different vertebrate proteins. Then two beetle predator species were placed in a cage with the eggs and allowed to feed as they chose. The gut contents of the predators were then tested for the protein markers. A diagram illustrates the experimental setup on the left; photos A and B show the egg exposures. (For illustrative purposes, egg densities in the photographs are greater than the densities used in the predator feeding choice study.) (Image originally published in Hagler and Mostafa 2019, Journal of Insect Science)