Several of the creatures living in the darkness of Mirkwood had acquired dark colouration, from squirrels to moths, and the butterflies living in the treetops were no exception. These butterflies seem to have been related to the 'purple emperor', a real type of butterfly with patterned wings of white and iridescent blue. The 'black emperors' of Mirkwood had no such markings, with their wings showing instead as plain and black. They were prey to the many spiders that lurked among the trees of the Forest.