Abstract
Lampyrinae Lucidotini contains nearly a third of the world's Lampyridae. The lack of revisions and the overlap of diagnostic features across taxonomic levels have hindered identification and, therefore, further studies of Lucidotini taxa. The use of terminalia and genital traits in Lucidotini phylogenies has been fundamental to inform and update the genus-level delimitations in this group. One important open question is whether the presence of increased-length abdominal segment VIII (in relation to segment VII) in the closely related genera Scissicauda and Haplocauda is synapomorphic or homoplastic. In recent collecting efforts combined with studies of specimens deposited in different scientific collections, we found specimens hypothesized as four new firefly species from the Amazon basin that share the unique characteristics of the male abdomen of Haplocauda species. To test the hypothesis that these new species are monophyletic and sisters to Haplocauda species, and that the augmented segment VIII is synapomorphic to Scissicauda + Haplocauda, we ran phylogenetic analyses building upon a pre-existing character matrix, including a wide sample of Lucidotini and neighboring branches. Our results support the placement of the four new species described here (H. lata sp. nov., H. amazonensis sp. nov., H. aculeata sp. nov. and H. antimary sp. nov.) in Haplocauda. Importantly, one species with regular-sized segment VIII sclerites was recovered as the earliest diverging lineages of Haplocauda, suggesting that segment VIII was augmented at least twice in the Lucidotini-the other one being within Scissicauda. We also report, for the first time, a sympatry between Haplocauda species. We revised the definition of Haplocauda and updated the distribution of H. mendesi and the existing key to species.