Tracking switching behavior of Trichogramma brassicae (Hymenoptera: Trichogrammatidae) over 45 generations

The effects of long-term rearing of Trichogramma brassicae (Bezdenko) on host preference and switching behavior was examined when parasitizing two common factitious hosts, including Mediterranean flour moth (MFM), Ephestia kuehniella Zeller and Angoumois grain moth (AGM), Sitotroga cerealella (Olivier) over 45 generations. Both host species eggs were offered to the parasitoid over 24 h. Significantly more MFM eggs were parasitized in all generations, but a distinct negative switching behavior was found in all experiments. The parasitoid negatively switched from MFM when they became abundant compared to AGM and vice versa. The preference coefficient (c) estimated using Murdoch's index ranged from 2.056 (in G5) to 1.734 (in G45) for MFM and 0.486 (in G5) to 0.577 (in G45) for AGM. The linear regression indicated that despite preferring MFM, the intensity of the preference decreased over 45 generations. Negative switching behavior in T. brassicae may be advantageous for this species in controlling pests in given situations.