Abstract
Body size is a main fitness component of insect parasitoids. We assessed the potential influence of maternal size of the parasitoid wasp Aphidius colemani Viereck (Hymenoptera: Braconidae: Aphidiinae) on its ability to parasitize the different instars of Aphis gossypii Glover (Hemiptera: Aphididae) on eggplant and cucumber. In the experiments vs parasitoid females were used. Females oviposited in all instars but more of the smaller hosts were parasitized. Host selection was affected by female size and the larger hosts were more frequently mummified by the large than the small females. Thus, parasitoid female size influ- enced host selection. This could affect the potential of the parasitoid to exploit populations of aphids that differ in their size structure. The importance of these results in terms of the ecological adaptations of the parasitoid and their implication for biological control are discussed.
Highlights
Changes in the behaviour of optimal foragers results in an increase in profitable gain when exploiting resources of variable quality
Myzus persicae (Sulzer), and Aphis gossypii Glover (Hemiptera: Aphididae), are suitable hosts for the development and reproduction of this parasitoid, and it prefers to oviposit in the first- and secondinstar nymphs (Perdikis et al, 2004)
A. colemani is widely used in the biological control of A. gossypii and M. persicae infesting greenhouse crops, the factors that influence its host selection are poorly studied (Grasswitz, 1998)
Summary
Changes in the behaviour of optimal foragers results in an increase in profitable gain when exploiting resources of variable quality. These adaptations are difficult to investigate as resource quality and quantity may vary in space and time. The key feature is that their development is entirely dependent on the resources provided by a single host. Based on their development and host usage strategies parasitoids have been divided into two groups: koinobionts and idiobionts (Askew & Shaw, 1986). Koinobiont parasitoids allow further development of the host after parasitism, whereas idiobionts parasitize nongrowing hosts (eggs or pupae) and /or arrest the development of hosts by paralysis or killing it during oviposition
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