The life histories of caterpillars are thought to reflect their coevolutionary relationships with host plants. Studying the evolution of herbivorous insects is complicated because of their species richness, wide range of niches and ecosystems, and their ability to feed on a variety of plants. I have been working in a project at the FLMNH to better understand the diversity of Neotropical butterflies through ‘DNA barcodes’. This short DNA sequence can be used to study similarities and differences among individuals in some difficult groups to determine how many species are present. I will be barcoding caterpillars collected in Ecuador during several decades of research on two major groups of butterflies, Adelpha and Ithomiini. These caterpillars are associated with information on their host plants, larval development, larval appearance and behavior, but because they died before reaching adult, they are unidentified and the associated information is useless. I will match these unidentified caterpillars to adult butterflies, making available their life history information and likely resulting in discoveries of new host plant associations and immature stages. Expanding our knowledge of the immature stages of these butterflies will contribute to ongoing studies on their coevolution with host plants and their diversification.