Abstract
We investigated the influence of the hymenopteran parasitoid Perilitus sicheli Giard (Braconidae) on the pattern of mating and mate choice processes in the Chrysomelid beetle Timarcha maritima Perris. In the field, the prevalence of infection was higher in unpaired males and females than in paired individuals, although this result was significant only for males. The size of infected and uninfected individuals was not significantly different. The fecundity was significantly reduced by the infection in females. However, in experimental conditions males were unable to detect and to avoid infected females as sexual partners. We discuss the possible reasons for this absence of preference.