[Surface drainage systems and their colonization by Lymnaea trunculata Müller. Apropos of 4 years of observations in Haute-Vienne, France].

The colonization of superficial draining systems of four damp meadows by Lymnaea truncatula was studied during four years. The speed of snail migration was high from February - March to June - July, but reduced from September to January. This speed was also higher in draining ditches than in principal furrows. The colonization of draining systems was delayed from 25 to 27 months when barrages were set in principal draining furrows. The significance of these observations is discussed.