In addition to potential direct effects on primary producers and herbivores, desiccating conditions may mediate higher-order effects on food webs such as trophic cascades. We examined the influence of desiccating conditions on entomopathogenic nematodes (EPNs), common natural enemies of many soil-dwelling insects. Desiccation studies were conducted using the host Galleria mellonella (Lepidoptera:Pyralidae, wax moth larvae) and compared three broadly-distributed EPNs (Heterorhabditis bacteriophora, Steinernema carpocapsae, and Steinernema riobrave) to investigate how foraging strategy or native habitat might affect desiccation tolerance. Weights of individual nematode-killed hosts were tracked daily during desiccation, and cohorts were placed into emergence traps when average mass losses reached 50%, 60%, 70%, and maximum levels. We tracked the proportion of nematode-killed hosts producing infective juveniles (IJs), the number and infectivity of IJs produced from desiccated cadavers, and the influence of soil water potentials on the rehydration of desiccated hosts. We observed significant differences in the desiccation rate among the three species (P<0.05), and also saw significant differences among the three species in both the proportion of hosts producing IJs (P<0.0001) and IJ production per host (P<0.001). Overall, the nematode Steinernema carpocapsae (an ambusher) exhibited the greatest desiccation tolerance, with higher rates of infection success and IJ production than the other two species, which exhibit a more mobile foraging strategy. S. riobrave exhibited little tolerance for our desiccation procedure despite its prevalence in hot, arid climates, suggesting that that foraging strategy may be a better predictor of tolerance to desiccation in these nematodes than native habitat.
