The non-native Otala punctata (Müller, 1774) is a helicid snail which was imported into Malta through a plant nursery in Mosta. The established population was studied in 2008 by Barbara & Schembri, who mapped its range around the nursery responsible for its introduction. This map is copied and pasted beneath; the part highlighted in yellow by Barbara & Schembri shows the range of the species as in 2008. The red shows the plant nursery itself, while the dark grey shows the studied area. 
Today, a substantial number of specimens was found further to the north of the yellow area. I have covered the 'newly colonized' area in blue to give an indication as to its extent. Apparently this snail is very well adapted to the kind of anthropogenically disturbed habitat presented in the vicinity, and will continue to colonize new areas and advance as predicted in the 2008 paper. The larger its range becomes, the less anything can be done to exterminate it, which is very bad news for native (and less aggressively competitive) snails.
*The photograph of the Otala punctata specimen above was taken at point 'a'.
Reference:
Barbara N. & Schembri P. J., 2008. The status of Otala punctata (Müller, 1774), a recently established terrestrial gastropod in Malta. Bollettino Malacologico, 44 (5-8): 101-107.
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