Abstract
Age of host eggs can be a limiting factor for egg parasitoids. It is expected that old eggs are less preferred by egg parasi- toids, which can discriminate between eggs of different ages by using chemical cues. The objective of this study was to determine the preference, development and arrestment of Telenomus remus Nixon (Hymenoptera: Scelionidae) parasitizing Spodoptera frugi- perda (J.E. Smith) (Lepidoptera: Noctuidae) eggs of different ages. This egg parasitoid preferred to parasitize 1- and 2-day-old eggs rather than 3-day-old eggs in choice and no-choice assays. However, although the percentage emergence of parasitoids is signifi- cantly lower from 2- and 3-day-old eggs, the sex ratio and developmental time are unaffected. Parasitoids spent longer searching substrates impregnated with extracts of 1- and 2-day old eggs than 3-day-old eggs. Our results reveal that T. remus is able to distin- guish the most suitable (1-day-old) from the least suitable (3-day-old) host eggs, but unable to recognize the unsuitability of interme- diate aged eggs. Egg arrestants may be responsible for the preference of T. remus for ovipositing in 1- and 2-day old eggs.
Highlights
Host selection by parasitoids consists of the following behavioural steps: host habitat location, host location, host recognition and host acceptance (Vinson, 1976; 1984)
These effects may be due to changes in the chemical composition as nutrients are gradually consumed by the host embryo and/or changes in the physical characteristics of the chorion, which becomes more rigid as the egg ages (Barret & Schmidt, 1991; Bai et al, 1992)
Mean percentage parasitoid emergence significantly decreased with egg age
Summary
Host selection by parasitoids consists of the following behavioural steps: host habitat location, host location, host recognition and host acceptance (Vinson, 1976; 1984). Old eggs are less suitable as hosts as they adversely affect several parasitoid biological parameters, such as percentage parasitism, developmental time (Da Rocha et al, 2006), adult emergence (Bruce et al, 2009), body size and sex ratio (Ruberson & Kring, 1993). These effects may be due to changes in the chemical composition as nutrients are gradually consumed by the host embryo and/or changes in the physical characteristics of the chorion, which becomes more rigid as the egg ages (Barret & Schmidt, 1991; Bai et al, 1992). Parasitoids might make use of the physical characters and/or chemicals in and on the surface of eggs, which change with age, as cues indicating the suitability of hosts
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