[...] Distinguishing between [Plusia putnami and Plusia festucae] is by no means easy, even in the presence of series, which only go to reveal the range of variability of each, and definite records must rely on genital examination. [...] In Durham it is fairly widespread throughout the three river valleys and their tributaries, even up to Langdon Beck in Upper Teesdale. There are no records, however, from sites on the eastern Magnesian Limestone plateau, presumably because of the scarcity of wetlands where the foodplants can grow.