none Agrotis ipsilon; CHEMICAL-SIGNALS; Kairomones & sex pheromones, hymenopteran parasite responses; HYMENOPTERAN-PARASITES; Apanteles ruficrus; Parasite attraction & prevalence responses to host kairomones & pheromones Spodoptera littoralis; CHEMICAL-SIGNALS; Kairomones & sex pheromones, hymenopteran parasite responses; HYMENOPTERAN-PARASITES; Microplitis demolitor; Parasite attraction & prevalence responses to host kairomones & pheromones Apanteles ruficrus; CHEMICAL-SIGNALS; Kairomones & sex pheromones of lepidopteran hosts, attraction responses; TAXIS-; Attraction responses to lepidopteran host kairomones & sex pheromones; LEPIDOPTERAN-HOSTS; Agrotis ipsilon; Host kairomones & sex pheromones, attraction & prevalence responses Microplitis demolitor; CHEMICAL-SIGNALS; Kairomones & sex pheromones of lepidopteran hosts, attraction responses; TAXIS-; Attraction responses to lepidopteran host kairomones & sex pheromones; LEPIDOPTERAN-HOSTS; Spodoptera littoralis; Host kairomones & sex pheromones, attraction & prevalence responses Kairomones and two sex pheromones were tested on two larval parasitoids, Apanteles ruficrus and Microplitis demolitor. Adult females of A. ruficrus were attracted to the kairomone extracted from the host larvae, Agrotis ipsilon. At the same time, the synthetic sex pheromone of A. ipsilon revealed a strong kairomonal effect on the adult females of the parasitoid. Similar effects were obtained with M. demolitor when the kairomone extracted from Spodoptera littoralis was used. In field experiments, A. ipsilon and S. littoralis kairomones significantly raised the rate of parasitism from 5.6 and 11.8% in control plots to 19.5 and 26% in treated plots by A. ruficrus and M. demolitor, respectively. Meanwhile, kairomones extracted from larvae of Autographa ni and S. exigua showed less effect on the two tested parasitoids.