HOST RECOGNITION BY ENTOMOPATHOGENIC NEMATODES - BEHAVIORAL-RESPONSE TO CONTACT WITH HOST FECES

Host recognition by entomopathogenic nematodes may occur through conta ct with insects' excretory products, cuticle, or gut contents. We anal yzed the behavioral responses of four species of entomopathogenic nema todes during contact with feces of natural or experimental hosts. Host recognition by nematodes was manifested in alterations in the frequen cy and/or duration of one or more search parameters including forward crawling, head-waving, body-waving, stopping, backward crawling, head- rubbing, and head-thrusting. Heterorhabditis bacteriophora and Steiner nema glaseri showed behavioral responses to contact with feces of thei r natural hosts, Spodoptera exigua (Lepidoptera) and Popillia japonica (Coleoptera), and to the experimental hosts, Acheata domesticus (Orth optera) and Blatella germanica (Blatteria). Steinernema carpocapsae re sponded only to B. germanica feces, whereas S. scapterisci did not sig nificantly respond to any of the insect species. During contact with c ockroach feces, all nematodes, except S. scapterisci, showed avoidance behavior. We suggest that ammonia present in cockroach feces is inhib itory to nematodes. Specific host recognition by entomopathogenic nema todes may be an important mechanism to maintain host affinities.