Genetic variability in the reactive distance in Trichogramma brassicae after automatic tracking of the walking path

Efficiency of hymenopterous parasitoids to control pests in a biological control release program probably increases with increasing searching ability of the females, which, in return, likely depends on the distance from which females perceive their hosts (i.e., reactive distance). In this study, we first analyse this hypothesis with the help of a stochastic model simulating the walking path of isolated Trichogramma females during their searching behaviour. Then, this reactive distance is estimated using automatic recording and analysis of the walking path of female wasps. Finally, the genetic variability for this trait is analysed in a Trichogramma brassicae Bezdenko (Hym.; Trichogrammatidae) population. Three types of hosts were used: Eggs ofEphestia kuehniella Zeller (Lep.; Pyralidae), eggs of Mamestra brassicae L. (Lep.; Noctuidae) and 0.45 mm glass beads. M. brassicae eggs are perceived from 4.01 d: 0.15 mm, which is a significantly longer perceptive distance than for E. kuehnieUa eggs (3.69 :t: 0.10 mm) and glass beads (3.67 -4- 0.10 ram). Moreover, whatever the host tested, a significant genetic variation is observed in this trait in the population studied. The ecological and evolutionary implications and the agronomical importance of these results are discussed.