Haplocauda, a New Genus of Fireflies Endemic to the Amazon Rainforest (Coleoptera: Lampyridae) †

SIMPLE SUMMARY: The Amazon Rainforest is still a frontier in the study of insect biodiversity, housing several species yet to be described and studied. Yet, its continuous deforestation urges scientists to study insect diversity there before it is too late. Here, we identified and described new species and a new genus of fireflies from the Amazon Rainforest. These new species are unique among other fireflies due to their unique abdominal morphology, supposed here to involve a clamping mechanism used during mating. ABSTRACT: Most firefly genera have poorly defined taxonomic boundaries, especially in the Neotropics, where they are more diverse and more difficult to identify. Recent advances that shed light on the diversity of fireflies in South America have focused mainly on Atlantic Rainforest taxa, whereas lampyrids in other biomes remained largely unstudied. We found three new firefly species endemic to the Amazon basin that share unique traits of the male abdomen where sternum VIII and the pygidium are modified and likely work as a copulation clamp. Here we test and confirm the hypothesis that these three species form a monophyletic lineage and propose Haplocauda gen. nov. to accommodate the three new species. Both maximum parsimony and probabilistic (Bayesian and maximum likelihood) phylogenetic analyses confirmed Haplocauda gen. nov. monophyly, and consistently recovered it as the sister group to Scissicauda, fireflies endemic to the Atlantic Rainforest that also feature a copulation clamp on abdominal segment VIII, although with a different configuration. We provide illustrations, diagnostic descriptions, and keys to species based on males and females. The three new species were sampled from different regions, and are likely allopatric, a common pattern among Amazonian taxa.