Abstract: This paper provides a map showing the area of the Debrecen supercolony of the invasive garden ant (Lasius neglectus Van Loon, Boomsma & ANDRÁSFALVY, 1990) in 1998, 2000, and 2002. Vegetation types are marked on the map. The presence of different ant species' nest entrances was also mapped in 10 cm long sections along a transect through the L. neglectus supercolony in 1998 and 2002. The expansion of L. neglectus was not equal in the different directions and in the different years. It seems that L. neglectus spreads fastest on paths, and does not spread rapidly in shady and cool areas occupied by coniferous bushes. Records showing isolated localities of L. neglectus colonies confirm that this species is budding. The data suggest that the relative L. niger (Linnaeus, 1758) is more impacted by the invasion of L. neglectus than Tetramorium cf. caespitum (Linnaeus, 1758). Moreover, Liometopum microcephalum (Panzer, 1798) and Lasius fuliginosus (Latreille, 1798) were able to completely defend their territory against L. neglectus. From 1998 to 2002, the number of 10 cm long sections containing L. neglectus nest entrances doubled, and the number of sections unoccupied by any ant species decreased by half.