Effects of the host species and the number of parasitoids per host on the size of some Trichogramma species (Hymenoptera : Trichogrammatidae)

The size of some Trichogramma spp. adults and especially the ovipositor len gth depends on the species, but is also related to the host species and to the number of parasitoids per host. The length is greater in T. evanescens than in T. pretiosum itself greater than in T. exiguum, but the width is si milar in the three species. For T. evanescens, the size obtained in Mamestr a brassicae host when three or four insects emerged is similar to that obta ined in Ephestia kuehniella host when singly parasitized. The size of the o vipositor is important because it may influence the possibility of in vitro egg laying in artificial host eggs. A shorter or a narrower ovipositor cou ld cause difficulties in egg-laying into artificial host eggs composed of a membrane of unsuitable thickness.