Technical Abstract: Our objective was to estimate the biocontrol potential of the recently discovered entomopathogenic nematode species, Heterorhabditis mexicana (MX4 strain). In laboratory experiments, we compared H. mexicana to several other entomopathogenic nematodes for virulence to several insect pests, environmental tolerance (to heat, desiccation and low oxygen levels), and host seeking ability. Heterorhabditis mexicana expressed low or intermediate capabilities in all traits except in host seeking ability and virulence to the lesser mealworm, Tenebrio molitor, for which no differences among nematodes were detected. Heat tolerance was more than five fold greater in Steinernema riobrave than H. mexicana, H. indica, and H. bacteriophora. Mortality of nematodes following exposure to low oxygen levels was lowest in S. riobrave followed by glaseri and higher in the other species (H. mexicana, H. bacteriophora, and H. indica). The apparent superiority of S. riobrave in heat and low oxygen tolerance is likely to be advantageous in biocontrol programs. We conclude that H. mexicana exhibits a cruiser type of search strategy and, relative to other entomopathgenic nematodes, generally possesses moderate abilities in biocontrol traits.