The bee tribe Anthidiini in Singapore consists of two genera, Euaspis and Anthidiellum, with the latter newly documented for the country. We detected adults of Anthidiellum (Pycnanthidium) smithii smithii (Ritsema, 1874) foraging on flowers at the Dairy Farm Nature Park near the Bukit Timah Nature Reserve—Singapore’s highest quality remnant forest patch—nesting in bamboo stem trap-nests. Identification of the Anthidiellum subspecies was confirmed through study of regional material including the type specimen of Anthidium minutissimum Bingham, 1903 (considered to be a junior synonym of Anthidiellum smithii smithii), in the Natural History London, which proved to be a male whereas the original description cited it as a female. Nesting materials and nest architecture of Anthidiellum smithii smithii are compared with those of two other Asian species within the subgenus Pycnanthidium and with the other comparably smallbodied Singapore cavity-renting Megachilinae, Heriades (Michenerella) othonis Friese (Osmiini, a new record for Singapore). Euaspis, a genus of cleptoparasitic bees, is represented in Singapore by Euaspis polynesia Vachal, 1903, a widespread Southeast Asian species, along with a second species, probably undescribed, discovered foraging on flowers of Syzygium zeylanicum at Kent Ridge Park. Diagnostic features of this bee are illustrated as are those of a Euaspis female from Laos that may or may not prove to be conspecific. These enigmatic Euaspis are compared to Euaspis polynesia and to Euaspis aequicarinata Pasteels, 1980, the latter newly recorded from Peninsular Malaysia based on a female specimen examined. Distributional records for all three species of Singapore Anthidiini are summarised and mapped. A total of 29 species (including morphospecies) of family Megachilidae are now recorded for Singapore, out of a total known fauna of ca. 102 named species and 25 additional morphospecies. The 29 megachilids comprise, in addition to the three Anthidiini species, 20 Megachile species reported in a previous paper, two species of Lithurgus (Lithurgini), three species of Coelioxys including an undescribed (Torridapis) (Megachilini, a new subgeneric record for Singapore), and one Heriades species. Notes on the regional anthidiine fauna include new generic and subgeneric records for Laos and Cambodia, reclassification of Dianthidium selangorense Cockerell, 1927, as Anthidiellum (Clypanthidium) selangorense (Cockerell, 1927), and a new record of Anthidiellum (Ranthidiellum) ignotum Engel from Phayao Province in Thailand.

Reports of global bee declines have raised an urgent call for assessments of the conservation status of these key pollinators. The first published checklist and conservation status assessment for the bee fauna of a Southeast Asian country is presented here. A total of 133 species, comprising 106 named species and an additional 27 distinct morphospecies, have been recorded in the Singapore checklist. Conservation statuses were assessed for all species using a decision table adapted from the IUCN Red List criteria, accounting for documented site occurrences, habitat associations, and year of last record. Of key conservation importance are six Nationally Extinct species, six Critically Endangered species, two Endangered species, and 12 Vulnerable species. A relatively high proportion of stingless bee species (five of fourteen) in tribe Meliponini are either Nationally Extinct or Critically Endangered, suggesting that these highly eusocial bees are of particular conservation concern. Whereas 16 bee species have been recorded only from historical records (from 1976 or before), 117 species persist (recorded 2009–2021), with 79 (68%) of these in urban or semi-urban areas such as city parks and rooftop gardens. The 44 (33.1%) Data Deficient species are poorly known locally and continued monitoring and inventorying of bees is needed to inform management of Singapore’s pollinators. Several bee species have only recently been confirmed for Singapore. Some synonymies and taxonomic comments presented first in a recently published book on Singaporean bees are discussed. Eupetersia (Nesoeupetersia) malayensis (Blüthgen, 1927) is treated as a provisional senior synonym of Eupetersia (Nesoeupetersia) singaporensis Pauly, 2012, and E. (N.) sabahensis Pauly, 2012. We recognise Trigona (Tetragonula) pagdeniformis Sakagami, 1987, as a junior synonym of the Trigona laeviceps Smith, 1857 (non auct.), with current combination Tetragonula (Tetragonula) laeviceps (Smith, 1857), and recognise Tetragonula (Tetragonula) valdezi (Cockerell, 1918) as a valid species.