Parasitic nematodes infect billions of humans, animals, and plants across the globe, yet the genetic mechanisms that differentiate development of parasitic versus free-living nematode lifestyles remain largely unknown. The dauer hypothesis, a long-standing theory on the mechanisms underlying the evolution of parasitism, posits that the dauer stage of free-living nematodes, such as of the model organism Caenorhabditis elegans, is a pre-adaptation to the infectious third stage larva of parasitic nematodes and thus similar genetic mechanisms are hypothesized to control both. Dauer formation in C. elegans is regulated by three molecular pathways, and we therefore sought to identify homologs of the genes present in these signaling pathways in a monophyletic clade of free-living, facultative, and obligate parasitic nematodes.