This dataset contains taxanomic and neuropil volume measurements of wild caught heliconiine butterflies, as well as kenyon cell and synapse counts in the mushroom body calyx of insectory -reared heliconiine butterflies. Wild caught butterflies were sampled from five locations in Central and South America between 2012 and 2016. Locations included Costa Rica, Panama, French Guiana, Ecuador, and Peru. These locations covered a range of habitats from dry to wet forest, at elevations from sea level to 2500m. Interspecific data from wild caught individuals include identification to a species level, sex, and body size, as well as volume measurements of the mushroom body structures, central brain, medulla, and antennal lobe. Measurements of mushroom body calyx volume, and estimates of Kenyon cell and synapse counts are included for six species of insectary-reared adult heliconiine butterflies (Agraulis vanilla, dryas iulia, eueides Isabella, heliconius melpmonene, heliconius Hortense, heliconius hecale). Two species (dryas iulia, heliconius charthonia) were also sampled for microglomeruli counts. This dataset was created as part of a NERC Independent Research Fellowship NE/N014936/1, to analyse the evolutionary expansions in mushroom body size in Heliconius butterflies, compared to their closest relatives. Full details about this dataset can be found at https://doi.org/10.5285/de62eff7-6ea4-44d7-a015-2eb9b25cf882