Organisms have evolved a diverse array of recognition systems; the most well-understood systems are present in the nematode species Caenorhabditis elegans and Pristionchus pacificus. Nematodes are among the largest phyla, exhibit simple locomotion, and have a common nervous system; thus, they are good model organisms for the investigation of diverse array of recognition systems. However, little is known regarding differences in recognition systems among nematode species. Here, we show that conspecific recognition systems differ among predator nematode species in terms of accuracy. Although the predator nematode Seinura caverna avoided feeding on conspecifics and related predator species, a previous study showed that the predator P. pacificus can distinguish self-progeny from the progeny of closely related strains. Furthermore, our results imply that S. caverna achieves hierarchical conspecific recognition by combining chemical cues with physical resources. A similar hierarchical conspecific recognition mechanism has not been reported in P. pacificus. Because S. caverna possesses traits that are useful in genetic studies of recognition systems, it provides a useful model for the understanding of recognition diversification at neural and genetic levels.