Deroceras invadens did not get easier to find in Belgium 1972–83. Ratio of the number of Belgian 10 km grid squares in which D. invadens was found to those in which D. reticulatum was found, for each year reported by Van Goethem et al. (1984). Numbers above and below the line are the counts for D. invadens and D. reticulatum respectively.

  
 
  Part of: Hutchinson J, Reise H, Robinson D (2014) A biography of an invasive terrestrial slug: the spread, distribution and habitat of Deroceras invadens. NeoBiota 23: 17-64. https://doi.org/10.3897/neobiota.23.7745