The olfactory sense is crucial for organisms, facilitating environmental recognition and inter-individual communication. Ithomiini butterflies exemplify this importance not only because they rely strongly on olfactory cues in both inter- and intra-sexual behaviours, but also because they show re-emergence of macro-glomerular complexes (MGCs). These specialized structures within the antennal lobe, lost in butterflies, but present in moths where they enable the integration of information from various types of pheromones, refining responses to specific cues. In this study we present high-quality genome assemblies for four Ithomiini species, investigating chemosensory evolution and associating expression profiles with neuroanatomical differences. We found that antennal transcriptomes across species exhibit profound divergence, indicating distinct species adaptations in environmental sensing. Noteworthy, sexual dimorphism is also characterised both in chemosensory genes and non-chemosensory genes, suggesting their relevance in behaviour. Lipid-related genes exhibit sexual dimorphism, potentially linked to pheromone production or host selection. The study broadens the understanding of antennal chemosensory adaptations in butterflies, highlighting the intricate interplay between genetic diversity, ecological specialization, and sensory perception with neuro-anatomical differences. Insights into chemosensory gene evolution, expression patterns, and potential functional implications enhance our knowledge of sensory adaptations in butterflies, laying the foundation for future investigations into the genetic drivers of behaviour, adaptation, and speciation in insects.