Entomopathogenic nematode foraging strategies - is Steinernema carpocapsae really an ambush forager?

For many years, entomopathogenic nematodes have been classified as either 'ambush', 'cruise' or 'intermediate' foragers. Here, we critically examine the evidence that Steinernema carpocapsae, the most studied 'ambush' forager, does actually use an ambush foraging strategy in nature. We propose an alternative hypothesis for the characteristic behaviours of S. carpocapsae (and other supposed 'ambush' foragers) based on adaptation to habitats other than mineral soils in which S. carpocapsae can 'cruise'. Several papers are reviewed in which S. carpocapsae was used successfully to control sedentary or cryptic pests in organic habitats, thus supporting our hypothesis. If this hypothesis is correct, it does not preclude S. carpocapsae (or any entomopathogenic nematode species) using an ambushing strategy under certain circumstances, but we believe on current evidence that the classification of S. carpocapsae as an ambush forager cannot be sustained.