Ecologie et ethologie d Ixodes ricinus L. en Suisse (Ixodoidea: Ixodidae). Troisieme note: copulation, nutrition et ponte..- By catchings of females of Ixodes ricinus in the field and by rearing in laboratory on guinea pigs, the author shows: l) that a great number of females mate in the field before climbing on the host, which ensure their feeding in normal delays. This number is submitted to local and seasonal variations. The amplitude and the causes of these variations are to be specified. 2) that the females of Ixodes ricinus generally cannot engorge completely without mating, showing thus a behaviour similar to that of the other genus of the family.