An egg-in-worm (EIW) assay is a useful method to quantify egg-laying behavior. Alterations in egg laying can be a behavioral response of the model organism Caenorhabditis elegans to potentially harmful environmental substances such as those produced by pathogenic bacteria.
Gardner, M., Rosell, M., Myers, E. M. Measuring the Effects of Bacteria on C. Elegans Behavior Using an Egg Retention Assay. J. Vis. Exp. (80), e51203, doi:10.3791/51203 (2013).