Corpse assays facilitated rapid quantification of predatory behavior and were conducted as previously described (15 (link), 25 (link)). Briefly, to generate substantial quantities of larvae for use as prey, Pristionchus strains were maintained on E. coli OP50 bacteria until freshly starved, resulting in an abundance of young larvae. These plates were washed with M9 buffer, passed through two Millipore 20-μm filters and centrifuged at 377g to form a concentrated larval pellet of juvenile animals. Excess buffer was removed, and 1 μl of worm pellet was deposited onto a 6-cm NGM-unseeded assay plates. This resulted in roughly 3000 prey larvae on each assay plate. Assay plates were left for a minimum of 1 hour to allow larvae to distribute evenly over the plate. Young adult Pristionchus predators were screened for the required mouth form and transferred to empty NGM plates for 30 min to remove any excess bacteria from their bodies. Subsequently, 20 Pristionchus predators were added to assay plates and allowed to feed for 24 hours before removal, and the plates were scored for the presence of corpses.