Does risk of egg parasitism affect choice of oviposition sites by a moth? A field and laboratory study

作者：Sadek Medhat M^*; Hansson Bill S; Anderson Peter

来源：Basic and Applied Ecology, 2010, 11(2): 135-143.

DOI：10.1016/j.baae.2009.09.003

• Spodoptera littoralis
• Tritrophic interactions
• Enemy-free space
• Host plant choice

In many insects the eggs are highly vulnerable and egg parasitism can represent a major cause of mortality. It is thus important for the ovipositing female to find a protected site for her eggs. We have examined how egg parasitation can affect host plant choice by Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae). Ovipositing moths exhibited significantly higher preference for alfalfa compared to cotton, both in the laboratory and the field. However, larval performance, in terms of development rate and the attained larval and pupal weight, was significantly better on cotton than on alfalfa. In laboratory tests no difference in larval survival on the two host plants was observed. To test the hypothesis that seeking enemy-free space could be a factor behind the preference for alfalfa, the parasitation levels on the two plants were investigated. In field tests, the egg parasitoid Chelonus inanitus (Linnaeus) (Hymenoptera: Braconidae) parasitized a significantly higher number of egg batches on cotton than on alfalfa. Furthermore, the parasitoid was significantly faster in finding and parasitizing S. littoralis eggs on cotton than on alfalfa in a cage experiment. These findings support the assumption that the preference for the inferior larval food plant, alfalfa, reflects a search for a host plant species on which attacks by natural enemies are less likely. Possible factors accounting for the preference of S. littoralis for alfalfa and the higher parasitation rates on cotton are discussed.

• 出版日期2010