Egg limitation and the functional response of the parasitoid Campoletis grioti (Hym: Ichneumonidae)

Abstract

The hypothesis that mature egg availability during a parasitoid's lifetime affects the functional response, as well as a parasitoid's handling time and searching efficiency, was tested. Campoletis grioti Blanchard (Hym: Ichneumonidae) female parasitoids and Spodoptera frugiperda Smith (Lep: Noctuidae) host larvae were used as an example. Each female of C. grioti was confined with different host densities (6, 10, 30, 50, 80, 120 and 160 larvae/day) of first and second S. frugiperda instars until the female died. We found that C. grioti showed a type II functional response, with a reduction in the number of parasitized hosts in relation to female ageing. Handling time and searching efficiency increased over time. When we standardized the data simulating unlimited egg supply, the functional response, handling time and searching efficiency became constant throughout the parasitoid's life. We discuss the relationship between egg availability and functional response and its associated parameters, and its consequence on biological control programs.

Keywords:

• Spodoptera frugiperda
• parasitoid
• biological control
• oviposition

Acknowledgements

We thank Sol Degese for assistance in the laboratory, Juan Briano and Willie Cabrera for their contributions to improve the manuscript, and Arabella Peard that made useful comments. We also acknowledge Juan Corley and the two anonymous reviewers for providing valuable comments and criticism.