The species' range expansion might be facilitated by a release from brood parasitism in the recently colonized range (Menéndez et al. 2008; Phillips et al. 2010). By effectively removing 50% of each generation in native populations, Sarcophaga sexpunctata imposes a very strong mortality factor. Interestingly, S. sexpunctata is widely distributed in Europe and feeds on eggs of different spider species (Povolný 2000), yet, according to our results, does not parasitize on the expanding populations of C. punctorium. Northern European S. sexpunctata populations might require more time to adopt C. punctorium as a novel food source. Moreover, S. sexpunctata has been considered thermophilic and might show a decreasing population density with increasing latitude (Povolný et al. 2003).