[Motility and infestivity of first-stage Protostrongylid larvae. Factors of variation (author's transl)].

The infection of land-snails was realised in order to relate the motility of Protostrongylid first-stage larvae to their infectivity. Various factors such as the age of larvae, their density, the composition of the conservation liquid and the temperature were tried on the motility of larvae. A clear relation appeared between motility and infestivity of larvae. The age, density of larvae, and cold did influence negatively their motility. On the contrary increases in temperature and optimal concentrations of magnesium, calcium and sodium salts did influence positively the motility. Induced variations of motility did provoke related fluctuations of infestivity.