Scuticeratina: A new subgenus of small carpenter bees (Hymenoptera, Apidae, Xylocopinae) from Indomalaya

Small carpenter bees (<i>Ceratina</i>) are a morphologically diverse group of bees with a cosmopolitan distribution. The ~370 species of this group have been further classified in 25 different recognized subgenera. Here, a distinct new subgenus from Indomalaya, <i>Scuticeratina</i> <b>subgen. nov</b>., with two new species, <i>Ceratina ferruginea</i> <b>sp. nov</b>. and <i>Ceratina phukhaensis</i> <b>sp. nov</b>., are described. Two described species of previously uncertain subgeneric status, <i>C. muscatella</i> Nurse, 1902 <b>stat. rev</b>. and <i>C. splendida</i> Shiokawa, 2008 <b>stat. rev</b>. are also included within <i>Scuticeratina</i>. The monophyly of this group is supported by both morphological characters and molecular data, including phylogenetic analyses based on targeted genes and ultraconserved elements. Additionally, a third new species is tentatively placed in the nominate subgenus <i>Ceratina</i> Latreille, 1802, <i>C. sirikitae</i> <b>sp. nov</b>., distinct from other known species of this subgenus with unusual red abdominal coloration. Finally, an updated key to the <i>Ceratina</i> subgenera of the eastern hemisphere incorporating the new subgenus is provided.