THE worldwide loss and fragmentation of natural habitats’ has led to considerable theory on metapopulation dynamics(2-8), One modelling approach, using structured population models(9,10), predicts that metapopulations in which local dynamics are affected by migration may have alternative stable equilibria(11-17), We have tested this prediction with extensive data on the butterfly Melitaea cinxia(18,19). Here we show that the probability of local extinction decreases with increasing population size and increasing immigration rate, and that local populations tend to be larger in regions with higher density of extant populations(19), results consistent with model assumptions and predictions(13,17), Our results exhibit a bifurcation pattern indicating multiple equilibria(14), with a strikingly bimodal distribution of the fraction of occupied habitat in 65 semi-independent patch networks, These results help to explain observations of species occupying either most, or very little, of the suitable habitat in well-connected patch networks(14,20,21). Metapopulations with multiple equilibria may collapse unexpectedly to extinction even in landscapes degrading only slowly, Multiple equilibria make it difficult to predict the occurrence of species in fragmented landscapes.