Intensive mark-recapture studies have become standard in attempts to elucidate the conservation status of butterfly populations. In order to test the usefulness of this approach, such mark-recapture studies were conducted with two Euphydryas species: E. editha , a highly endangered resident of grasslands on serpentine soils, and E. chalcedona , a ubiquitous resident of widespread coastal chaparral. Detailed statistical analysis of the resulting data revealed few differences between the two species in most adult population parameters that have been measured in previous studies, despite the two species' disparate conservation status. This suggests that standard mark-recapture statistics alone are insufficient to reveal adult population features that distinguish species susceptible to extinction from those that are comparatively more secure.