This dataset presents taxonomic data, and neuropil volume measurements of sensory structures in the brains of wild caught ithomiini butterflies (Lepidoptera, Nymphalidae, Danainae), within a single community in Yasuní national park, Orellana Province, Ecuador, collected in 2011-2012. Variables measured include taxonomic detail, sex, mimicry ring, and the volumes of major sensory neuropils (the medulla, lobula plate, lobula, ventral lobula, accessory medulla, antennal lobe and anterior optic tubercule) and the central brain volume. This dataset was created to examine how sensory environments shape investment in sensory brain centers in butterflies, as part of a NERC Independent Research Fellowship NE/N014936/1. Full details about this dataset can be found at https://doi.org/10.5285/8056bba1-8370-4d2b-b537-018c79c8acb0