Ciidae is a cosmopolitan family with more than 780 extant described species in 61 genera. It is divided into two subfamilies: Xylographellinae, encompassing the tribes Xylographellini Kawanabe and Miyatake, 1966, and Syncosmetini Lopes-Andrade, 2008; and Ciinae, currently divided into Ciini Leach, 1819, and Orophiini Thomson, 1863. Ceracis Mellié, 1849 is the second most diverse genus within Ciidae, with 52 described species. Ceracis bicornis (Mellié, 1849) has been regarded as a cryptic species complex for the past decade, although it has never been redescribed, and numerous closely related specimens can be recognized in museum collections. We compare the external morphology of the type series and named individuals of Cer. bicornis with many morphologically similar specimens collected by our research group across several Brazilian states over the last two decades. We redescribe Cer. bicornis and designate the lectotype for Ennearthron bicornis Mellié, 1849. Furthermore, we describe four new closely related species from Brazil, previously identified as Cer. bicornis: Cer. artur sp. nov. from the Atlantic Forest biome (South Region of Brazil); Cer. glauco sp. nov. from the Atlantic Forest biome (Northeast Region); Cer. julio sp. nov. from the Amazon biome (North Region); and Cer. sergio sp. nov. from the Amazon and Atlantic Forest biomes (Southeast, North, and Northeast Regions). In addition, we provide a supplementary description of Cer. thoracicornis (Ziegler, 1845), the first Nearctic species formally included in the cucullatus group, together with the new taxa described herein. An identification key is also provided for males of all American species of the cucullatus group.
Souza-Gonçalves et al. (2026) studied this question.