Alteration of host behavioural phenotypes is a widespread strategy of host exploitation among parasitic organisms. Understanding such strategies is important for applied aspects of parasitology as well as for evolutionary and ecological reasons. In this proposal, we wish to study, from proximate and ultimate mechanisms to ecological consequences, a type of manipulation that has been until now largely unexplored: the bodyguard manipulation. In certain braconid wasps, larvae exit from the host to pupate and subsequently induce their hosts to behave as true “bodyguards” displaying a range of defensive behaviours that protect cocoons against natural enemies. Mechanisms behind bodyguard manipulations are enigmatic since, a priori, the host and the parasitoid are not anymore physiologically interacting. Another intriguing aspect is that, at least in associations between parasitoids and ladybirds, a significant proportion of parasitized hosts apparently recover after the wasp exits the cocoon, and are even able to reproduce. Why do host species accept to behave as a bodyguard? Is the host truly manipulated or does it collaborate to alleviate fitness costs? What are the molecular, the neurobiological and the physiological mechanisms of this behavioural change? What are the new attributes and properties of individuals that recover a normal behaviour? These timely questions have remained largely unexplored by parasitologists. In this project, by an integration of biochemical, ecological and evolutionary approaches including modelling, we wish to contribute to partially fill this gap, using the wasp Dinocampus coccinellae (Braconidae) and the ladybird Coccinella septempunctata as a model system.