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Abstract
Fireflies (Coleoptera: Lampyridae) are a family of beetles that exhibit great diversity. This diversity is present both in their morphology and in their sexual signaling. While fireflies are known for their bioluminescent flashes and glows used to find mates, not all adult fireflies produce light. Non-bioluminescent adults use pheromones to attract and locate mates instead. These differences in sexual signals are accompanied by differences in firefly morphology, specifically in the sensory organs used to detect light signals or pheromones. My dissertation aimed to investigate the morphological diversity of these signal sensors (i.e., eyes, antennae, and antennal sensilla), as well as the light producing structures (i.e., light organs) of fireflies. My second chapter focuses on the diversity of antennal sensilla in fireflies and on identifying potential sensilla used to detect pheromone signals. I found that sensilla morphotypes varied greatly across species. I also found that diurnal (pheromone signaling) firefly species have more sensilla overall, including more chemosensilla that can be used to detect chemicals (including pheromones), than nocturnal (light signaling) fireflies. These findings reflect the importance of chemosensilla in pheromone detection for diurnal species. Interestingly, the specific type of sensilla likely used to detect pheromones varies between species. The third chapter established the most comprehensive worldwide firefly phylogeny to date with 339 species and based on 458 anchored hybrid enrichment loci. This phylogeny determines the history of pheromones and bioluminescence signaling in adults and the evolution of light organ shapes using ancestral state reconstruction. I found that both bioluminescence and the diverse light organ shapes evolved multiple times independently during firefly evolution. I also tested the influence of phylogeny and signal type on the evolution of eye, antenna, and light organ size in a phylogeny-based analysis. Aspects of eye and antenna size are significantly influenced by phylogeny and by sexual signal type. This study not only sheds light on the evolutionary relationships of fireflies, and their morphological structures associated with sexual signaling, it also provides a valuable foundation for future evolutionary studies of the remarkable morphological and behavioral diversity in this beetle family.