The evolution of bioluminescence within the firefly genus Phausis (Coleoptera: Lampyridae)

Species in the North American firefly genus Phausis (Coleoptera: Lampyridae) are not commonly encountered in the field and can be rare in museum collections. Most firefly genera represent species where all adult males are either luminous or non-luminous. There are some cases where genera contain both luminous and non-luminous males. In this instance, the non-luminous species are usually the minority and appear to represent a loss of luminescence in the adult male. Phausis is the exception because only two out of the 10 currently described species have bioluminescent males, P. reticulata and P. luminosa. Previous phylogenetic analyses of the family Lampyridae have indicated that transitions from pheromone courtship signaling (non-bioluminescent) to the use of bioluminescent courtship signals is common, but the loss of luminescent signaling and back to pheromone use, is much less frequent. A phylogenetic analysis of the genus Phausis was conducted using morphological data to test the hypothesis that the evolution of bioluminescence in these adult males is a derived mode of signaling for the genus.