This dataset is part of the study of mimetic host shifts in an endangered social parasite of ants, which is a joint study of the NERC's Centre for Ecology & Hydrology(UK), the University of Oxford(UK), University of Bialystok(Poland), Polish Academy of Sciences(Poland) and UFZ Helmholtz Centre for Environmental Research(Germany). Combined with datasets collected from previous study, they compare the proportions of caterpillars of Maculinea rebeli being adopted by resident Myrmica ant species near Przemysl, Poland in autumn with proportions of successful survivors the following summer to establish host specificity of the socially parasitic butterfly species. The data comprise: the study year, the ant species, total number of ant nest, the number of caterpillar survivors found in the nest of each ant species, number of nests with caterpillar presence and total number of nests without caterpillar presence. They were obtained from one population for 4 years(Y2001, Y2003, Y2004, Y2005). Detailed research method can be found in Thomas et al. (2013) Mimetic host shifts in an endangered social parasite of ants. Proc. R. Soc. B vol. 280 no.1751. (doi: 10.1098/rspb.2012.2336) Full details about this nonGeographicDataset can be found at https://doi.org/10.5285/b472d635-d8fa-4c39-acfe-2b285ca0b9a8