HIERARCHICAL ORDER OF HOST CUES IN PARASITE FORAGING STRATEGIES

The importance of host cues to three species of steinernematid nematod es (Rhabdita: Steinernematidae) with different foraging strategies was compared. We presented host materials to nematodes in series to test responses to combinations of host cues. If a fixed hierarchy of cues i s followed during foraging, parasites should respond most strongly to cues offered in natural order. Steinernema cavpocapsae, an ambush fora ger, aggregated at the source of volatile host cues only after attachm ent to host cuticle. They also parasitized hosts more efficiently afte r contact with cuticle. Steinernema glaseri, a cruise forager, was una ffected by exposure to combinations of host cues. Steinernema feltiae, a nematode with characteristics of both ambushing and cruising, was a ffected by cue hierarchies when either contact or volatile cues were p resented first. Host-associated materials encountered out of the conte xt may not qualify as host cues for the ambush forager, S. carpocapsae . Perhaps the order in which cues are encountered is more predictable for ambushers than for cruisers. Therefore an ambusher's response to h ost materials has a more fixed contextual framework.