Host recognition behaviour predicts host suitability in the entomopathogenic nematode Steinernema carpocapsae...

Steinernema carpocapsae (Rhabditida: Steinernematidae) host recognition behaviour was assessed and compared with 2 measures of host suitability. Previous research showed that S. carpocapsae infective juveniles respond to host cues in a hierarchical order, with attraction to Galleria mellonella volatiles being stimulated by contact with G. mellonella cuticle. We measured host recognition behaviour by calculating the percentage response of S. carpocapsae infective juveniles to volatiles produced by G. mellonella last instars after the nematodes were exposed to the cuticle of 11 candidate arthropod hosts and 2 control surfaces. Host suitability was measured by nematode-induced mortality to candidate hosts at 2 nematode doses and the level of reproduction supported by each host. The highest recognition response was scored for Agrotis ipsilon (Lepidoptera: Noctuidae). This insect also incurred nearly 100% mortality due to nematode infection and supported the highest level of reproduction. Non-insect arthropods tested (Chilopoda and Isopoda) stimulated no behavioural response and were not susceptible to nematode infection. Other insect species elicited intermediate levels of the recognition response. There were significant correlations between behavioural response and nematode-induced mortality at the lower dose. The level of reproduction supported by the candidate hosts was also correlated with S. carpocapsae behavioural response.