Role of olfaction in host finding by aphid parasitoidAphidius nigripes (Hymenoptera: Aphidiidae).

The olfactory responses of the parasitoidAphidius nigripes Ashmead were investigated with a four-field airflow olfactometer. Female and male parasitoids did not respond to potato plants, the food plant of their host. However, females were strongly attracted by odors from a preferred host,Macrosiphum euphorbiae (Thomas), and also from less preferred hosts such asMyzus persicae (Sulzer) andAphis nasturtii Kalt. Moreover,A. nigripes females responded positively to odors from a nonhost aphid,Rhopalosiphum maidis Fitch. The honeydew produced by these four aphid species was also very attractive to females. Males did not respond to aphids or honeydew but were highly attracted by odors from conspecific female parasitoids.