The stations of Laciniaria biplicata (Montagu, 1803) on Zuid-Beveland (Province of Zeeland) are outlying posts of its present area of distribution in the southern part of the Netherlands and in Belgium. It is supposed that the species reached Zuid-Beveland via the river Scheldt in early historical time, when the division of land and water in the Deltaic region of the rivers Rhine, Meuse and Scheldt differed greatly from the present situation. As a consequence of the geographic changes in the region the stations of L. biplicata became isolated, and as flowing water of low salinity, the natural dispersal agent, was not longer available the species failed to enlarge the isolated part of its area.