Abstract: Evidence indicating that Lasius platythorax Seifert, 1991 can act as a temporary host of several Chthonolasius species is presented. Observations on the socially parasitic colony foundation of several Chthonolasius species in typical L. platythorax habitats in the Netherlands, Belgium and Slovakia are discussed. Two possible colony foundation strategies to take over L. platythorax-colonies are put forward.