Stercoralis is the species of the man and dog strongylid. The strongyloid's life cycle is heterogonic—it is more complex than that of most nematodes, with its alternation between free-living and parasitic cycles, and its potential for autoinfection and multiplication within the host. The parasitic cycle is homogonic, while the free-living cycle is heterogonic.
The heterogonic life cycle is advantageous to the parasite because it allows reproduction for one or more generations in the absence of a host. In the free-living cycle, the rhabditiform larvae passed in the stool can either molt twice and become infective filariform larvae (direct development) or molt four times and become free-living adult males and females that mate and produce eggs from which rhabditiform larvae hatch.
