Amongst the Lepidoptera, ultraviolet wing patterns are common. Where closely related species are sympatric, it has been thought that these patterns play a significant role in species recognition. In Europe, a number of Colias and Gonepteryx species of butterflies occur sympatrically, exhibiting similar visible and ultraviolet (UV) patterns. We analysed the UV and visible wavelengths, using reflectance spectrometry, for evidence of species specific UV colours. A great deal of variation was found to occur between reflected wavelengths of individuals but not between species. Individual variation in UV was so great that butterflies (or butterfly predators) would be unlikely to recognise particular species on the basis of UV colours. We suggest that variation in UV reflectance in male Pierid butterflies is more likely to be associated with mate choice by females or with male-male interactions.