For more than half of the time since the start of formal binomial nomenclature in 1758, the stingless bees were largely classified, with some minor exceptions (e.g., the earliest species were placed in Apis Linnaeus or Centris Fabricius), in either a single genus, Melipona, or into two genera, Melipona Illiger and Trigona Jurine. It was not until the works of Heinrich Friese (1860–1948) and Theodore D.A. Cockerell (1866–1948) that serious alterations to the classification were initiated, although most species were still placed in a massive, ill-circumscribed Trigona. These two authors were then followed by the extensive and detailed studies of Herbert F. Schwarz (1883–1960) and Jesus S. Moure (1912–2010), who effectively provided new interpretations for natural groupings of stingless bees, with the latter establishing the foundations for our current system of Meliponini. The growing biological data available for many species also served as a new source of character information for establishing groupings of these bees (e.g., Schwarz 1948). Subsequent to Moure, most changes to the supraspecific classification consisted of the addition of new taxa, largely through the efforts of João M.F. Camargo (1941–2009) and his collaborators in the New World and Shôichi F. Sakagami (1927–1996) in the Old World (e.g., Sakagami 1975, 1978, 1982). Contra these systems, Charles D. Michener (1918–2015) (Michener 1990, 2007a) and Alvaro Wille (1928–2006) (Wille 1963, 1979) tended to reduce the number of recognized genera, but the phylogenies of Rasmussen and Cameron (2007, 2010) corroborated many of the conclusions originally raised by Moure (1946, 1951, 1961, 1971), thereby necessitating a considerable reconsideration of their organization.

Here we present a brief overview of the revised supraspecific classification of Meliponini (M.S. Engel in Engel et al. 2021a), including keys to the genera and subgenera by region and summaries of distribution and identification tools for each genus, along with a checklist of currently recognized species. The three keys presented here allow for the identification of all currently recognized genera and subgenera of Meliponini. The keys are adapted from recent works that relate to the new organization of the tribe (Rasmussen et al. 2017; Engel 2019; Engel et al. 2021a) and are organized by geographic region, in the same manner as was done by Michener (2007a), although with a considerably different arrangement of genera. Naturally, there will always be disagreement over the recognition of particular groups and at what rank they should be classified, and different systematists will advocate for slightly different systems depending on their concepts of the groups. Even the authors of this chapter do not agree on all points of the current classification (e.g., whether Leurotrigona Moure should be removed from Trigonisca as its own genus, whether Dolichotrigona Moure should be recognized as a valid subgenus independent of Trigonisca s.str., whether Mourella Schwarz should be accorded generic rank, etc.). These finer points are all worthy of merit and undoubtedly will be revised in time. For now, we have followed the system as recently outlined in Engel et al. (2021a), with the exception of elevating Mourella as a genus and some additions from the last year (e.g., subgenera of Geotrigona Moure, Scaptotrigona Moure, and Scaura Schwarz) and herein (one new genus). Although we allude to some disparities and future subjects to be resolved, we do not intend here to emphasize justification or alternative interpretations, which are more fully explained in some of the recent publications cited herein. Regardless, the revised classification is based on comprehensive phylogenetic hypotheses for the tribe (Rasmussen and Cameron 2010).

Morphological terminology for the keys generally follows that used in major works on bees (e.g., Engel 2001a; Michener 2007a), although the terms of orientation for the legs follow that outlined by Engel et al. (2021a) and wing venation terms are from Rasmussen et al. (2017). Following the keys are brief summaries for each genus, along with a list of those currently recognized species in each taxon (subspecies and synonyms are not listed; species lists are current as of 29 June 2023).

In the New World, stingless bees are found from 34.89°S in Uruguay (Montevideo) and Argentina (Buenos Aires) up to 27.03°N in Mexico (Álamos, Sonora), at exceptional elevations up to 4000 m.a.s.l. in Peru and Bolivia (Camargo and Pedro 2007; Roig-Alsina and Alvarez 2017; Roubik and Vergara 2021). Meliponini are not native elsewhere in the Greater or Lesser Antilles, although extinct species of the genus Proplebeia Michener are known from the Miocene of the Dominican Republic and Chiapas, México. Camargo and Pedro (2007) and Camargo et al. (2013) provided a catalog of the Neotropical Meliponini. All Neotropical stingless bees belong to the subtribe Meliponina (Rasmussen and Cameron 2010; Engel et al. 2021a), a group not found in other regions of the world (Table 1). As of this writing we recognize 474 extant species in the New World and 26 extant genera.

This is a recently established genus for two species of minute stingless bees formerly included in Plebeia Schwarz and occurring from southern Mexico to Costa Rica. The species look like smaller species of Plebeia (e.g., subgenus Nanoplebeia Engel), at only ~ 3 mm length, but can be distinguished by the generally more matte integument and coarser sculpturing. Nesting biology has only been studied for Asperplebeia tica (Wille), which nests in tree cavities and, unlike the superficially similar Plebeia, builds brood clusters rather than combs, although species of Nanoplebeia also build brood clusters (Roubik 2021).

• A. moureana (Ayala)
• A. tica (Wille)

Cephalotrigona Schwarz includes modestly large bees (8–10 mm), which are generally dark brown to black with faint yellow marks. Noteworthy for the genus is the carinate to lamellate preoccipital ridge, the abundant facial punctation, the long legs, and spatula- or racket-shaped metatibiae with broad corbiculae and only simple setae on the retromarginal edge. Nests are built in tree hollows, and the entrances are a bee-sized hole on a short, rounded platform, built only with cerumen and dark solid materials. The honey is of good quality, and they usually store propolis in abundance. Colonies are large but they are not easy to manage in meliponiculture. This genus occurs from Colima and Jalisco, as well as in Tamaulipas, Mexico to Santa Catarina, Brazil and Missiones, Argentina. The most common species between Mexico and Colombia is Cephalotrigona zexmeniae (Cockerell), similar in appearance to Trigona (Koilotrigona) fulviventris Guérin-Méneville since both are black with a reddish orange metasoma but is larger, while the most common in South America is C. capitata (Smith). Currently, there are only keys for the species from Mexico and Central America (Ayala 1999) and a revision of the genus is needed.

• C. capitata (Smith)
• C. eburneiventer (Schwarz)
• C. femorata (Smith)
• C. oaxacana Ayala
• C. zexmeniae (Cockerell)

The two species of Duckeola Moure are robust bees of 8–9 mm length, found in Brazil, Ecuador, French Guiana, and Colombia. Perhaps the most striking feature of Duckeola is the considerably depressed parocular area between the compound eyes and the vertex, which elevates the vertex noticeably. In addition, the metatibia is noticeably claviform and lacks plumose setae on the retromarginal surface, and the mesotibial spur is absent (Oliveira 2002). No key to species is available but the two forms are quite distinct. Brood cells are arranged in clusters, although the nesting biology remains to be studied in detail.

• D. ghilianii (Spinola)
• D. pavani (Moure)

This is a genus of tiny bees, 3 mm in length, which look much like Plebeia, but have a reticulated matte integument, conspicuous abundant whitish pubescence, particularly on the face, and almost no yellow maculation on the face. The bees occur in southern Brazil and build irregular combs without an involucrum.

• F. schrottkyi (Friese)

The genus Frieseomelitta Ihering includes slender species of 4–7 mm in length, ranging from Sinaloa and Veracruz, Mexico to Mato Grosso do Sul, Brazil. Recognition of the genus is aided by the presence of yellow marks on the face bordering the compound eyes on the paraocular area and genae, the absence of the mesotibial spur, the enlarged and inflated metatibia with a small corbicular depression restricted to the apical third, and an overall spatulate or racket-shaped to claviform metatibia with plumose setae on the retromarginal edge. The shape of the metasoma is subtriangular when constricted, in dorsal view, in the varia species group, while the metasoma is elongate, even when contracted, owing to broader terga II and III (this is the situation in the nigra and portoi species groups). The nigra species group has a claviform metatibia, while the portoi species group has a baseball-bat-shaped metatibia. Adults soon turn black on the head and mesosoma after emergence but the metasoma remains whitish for more than a week. The milky white wing tip in most species is another distinctive feature. The nests are distinctive for the arrangement of brood in clusters. New species are being described and a key to species developed by FFO (pers. obs.).

• F. dispar (Moure)
• F. doederleini (Friese)
• F. flavicornis (Fabricius)
• F. languida Moure
• F. lehmanni (Friese)
• F. longipes (Smith)
• F. meadewaldoi (Cockerell)
• F. nigra (Cresson)
• F. paranigra (Schwarz)
• F. paupera (Provancher)
• F. portoi (Friese)
• F. silvestrii (Friese)
• F. trichocerata Moure
• F. varia (Lepeletier)

As the name of the genus suggests, species of Geotrigona nest in cavities in the ground. The species are generally robust, 5–7 mm in length, with a short broad metasoma. The genus is distributed from Michoacan, in the central Balsas River depression in Mexico to Santiago de Estero, Argentina. Camargo and Moure (1996) and Gonzalez and Engel (2012) provided keys to the species.

This is the most diverse genus of robber stingless bees, occurring from Nayarit and San Luis Potosi, Mexico to Argentina. Species of Lestrimelitta Friese are cleptobiotic (Roubik 1980; Bego et al. 1991), maintaining their nests by “stealing” the resources of other Meliponini and introduced Apis, often causing losses to stingless beekeepers. Lestrimelitta primarily rob brood provisions from their hosts, most frequently species of Nannotrigona, Scaptotrigona, Plebeia, and Melipona (Sakagami et al. 1993). During an attack on the host bees’ nests, most Lestrimelitta release a pheromone reminiscent of lemon (citral), which confuses the defense communication between workers and guards of the host (Breed et al. 2004.). Keys to identification are presented by Camargo and Moure (1989), Oliveira and Marchi (2005), Marchi and Melo (2006), Gonzalez and Griswold (2012), and Guevara et al. (2020). The shape of the propodeal spiracle (Ayala 1999) and the dimensions of the mesotibial spur (Oliveira 2002) are two important characters that allow, together with the pattern of body setation, for the separation of species.

Melipona includes almost all of the most massive meliponines. These robust bees, 9–14 mm in length, with abundant plumose pubescence on the mesoscutum have some superficial resemblance to the largest African Meliponula. The wings are usually short and only reach the posterior end of the metasoma or slightly exceed it. The integument is generally black, but in some species brown or pale brown, with yellow, ivory, or brown areas, while the mesosoma has pale, brown, or dark pubescence, particularly the mesoscutum. The genus can be found from Sinaloa and south of Tamaulipas in Mexico to northern Argentina. Many species are used in meliponiculture, and these were the first ‘semi-domesticated’ bees, subject to multiplication and husbandry in the prehispanic Mayan culture. Nest products such as cerumen and honey have been extensively used through the ages. Melipona is now the largest genus in the tribe, but modern keys are lacking. A key to the species was provided by Schwarz (1932) and for Mexican species by Ayala (1999), with a recent reassessment of species by Camargo and Pedro (2007).

This genus of little-known black bees from higher elevations (1400–2700 m) in Costa Rica and western Panama has an appearance superficially resembling Partamona Schwarz and Scaptotrigona. The shape of the metatibia is similar to that of Scaptotrigona, with a broader corbicula and with the characteristic large bristles arising from its surface as in Partamona.

• M. bivea Roubik, Lobo Segura, & Camargo

This is a monotypic genus, sister to the genus Schwarziana Moure, distributed in the southern portion of South America: Uruguay, Argentina, Paraguay, and Brazil (Paraná, Rio Grande do Sul, Santa Catarina). The sole species builds its nest in the soil and has architectural features typical to all other obligatory ground-nesting stingless bees (Camargo and Wittmann 1989). The head and mesosoma have conspicuous yellow maculation, while the remainder of the integument is weakly metallic, and the mesoscutum is largely shiny with distinct piligerous punctation. The genus is sometimes considered a distinctive subgenus at the base of Schwarziana (e.g., Engel et al. 2021a).

• M. caerulea (Friese)

This genus includes small bees (4–4.5 mm) with largely black integument and areas of yellow maculation on the mesoscutum, mesoscutellum, and legs. The punctation of the head and mesosoma is quite coarse. The mesoscutellum is projected posteriorly over the metanotum and, like the genus Scaptotrigona, there is a polished mediolongitudinal depression on the anterior margin and a prominent, deep, U- or V-shaped notch in the apical margin medially. The genus extends from Sonora (Rio Mayo, Sonora), Mexico — the farthest north in Mexico for any stingless bee lineage — to the south of Brazil (Rio Grande do Sul). The bees nest in holes of all kinds, including those in the ground as well as in trees. Despite storing comparatively little honey, some species show potential for agricultural pollination and are easy to manage in meliponiculture for this purpose. The genus was revised by Rasmussen and Gonzalez (2017), supplemented by Jaramillo et al. (2019).

Nogueirapis Moure differs from the closely related Partamona in the presence of abundant yellow markings; only slightly spoon-shaped, not greatly enlarged metatibia of the worker; as well as the smaller body size (3.5–5.5 mm), superficially resembling species of Plebeia. Like Partamona, there are one or two elongate bristles arising from the corbicular surface. Species nest in ground cavities but some also occasionally nest in tree hollows. A key to the species was presented by Ayala and Engel (2014) and Nogueira et al. (2020).

• N. batistai Nogueira
• N. butteli (Friese)
• N. costaricana Ayala & Engel
• N. minor (Moure & Camargo)
• N. mirandula (Cockerell)
• N. rosariae Nogueira

This genus includes the infamous “fire bees”, so named because of their characteristic defense system. Workers have well-developed mandibular glands that produce a secretion containing formic acid, and which can inflict significant burns to the recipient of an attack. The bees are orange to black in color, with the integument of the head quite smooth and polished, sometimes with a vitreous appearance. Overall, the bees are typically 5–6 mm in length, with the head large, wider in comparison to the mesosoma, with an enlarged malar space and an interocular distance greater than the length of the compound eye itself. Species range from Chiapas, Mexico to southern Brazil (Santa Catarina). A key to the species was provided by Gonzalez and Roubik (2008).

• O. chocoana Gonzalez & Roubik
• O. daemoniaca Camargo
• O. flaveola (Friese)
• O. huaoranii Gonzalez & Roubik
• O. ignis Camargo
• O. isthmina Gonzalez & Roubik
• O. mediorufa (Cockerell)
• O. mellicolor (Packard)
• O. mulfordi (Schwarz)
• O. obscura (Friese)
• O. tataira (Smith)

Species of Paratrigona Schwarz are small, between 3.5–5.5 mm in length, and are generally black with well-delimited yellow markings. The mesoscutellum projects posteriorly over the metanotum as a plate, and the metasoma is typically robust, almost as wide as the mesosoma. The genus occurs from Veracruz, Mexico to northern Argentina (Salta), and southern Brazil (Rio Grande do Sul). Some species nest on the ground, while others build nests in various substrates, including wood and termite mounds and often on vines and within epiphytic plants. A key to the species was provided by Camargo and Moure (1994).

This genus superficially resembles Paratrigona or Plebeia with a dull integument, but has the keirotrichiate area of the metatibia not depressed on the superior margin; has yellow markings on the paraocular area, frontal median line, and spots below the lateral ocelli; and the upper part of the preoccipital ridge lamellate and bordered by a row of robust setae. The genus includes a single species of ~ 4.7 mm in length and is currently known only from Colombia. The nesting biology remains to be documented.

• P. mayri Camargo & Roubik

Species of Partamona are usually 5–6.5 mm in length, with a smooth and shiny integument, which can be black to orange-yellow, depending on the species, with vitreous yellow paraocular markings. The metatibia is quite large and broadened, making it distinctively spoon-shaped, and lacks plumose setae on the retromarginal edge. Species build semi-exposed nests on either natural or human constructions or on trees, as well as in the ground. Nest entrances are built of a material similar to hardened mud, often with a wide entrance. Partamona are not appropriate for meliponiculture as they are quite defensive and challenging to work with, in addition to insignificant amounts of stored honey. The genus occurs from Sonora, Mexico to southern Brazil (Rio Grande Do Sul). The species with testaceous bodies were revised by Camargo (1980), and the entire genus by Pedro and Camargo (2003).

The genus Plebeia is a diverse group of often small and medium size bees (2–7 mm), with shiny integument bees and prominent yellow or white maculation. The metatibia is triangular shaped with only simple setae on the retromarginal edge, and the keirotrichiate zone of the retrolateral surface extends to the superior margin (without a shiny depressed rim). Included herein is the former genus Plectoplebeia Melo, an apparent synonym of the large subgenus Plebeia s.str. and representing merely larger, higher-elevation, seemingly cloud-forest specialized species of the subgenus (Engel 2022a). All features of Plectoplebeia intergrade into typical Plebeia s.str. as exemplified by comparison across species from one extreme to the other [e.g., Plebeia nigrifacies (Friese), P. aurantia (Engel), P. plectoforma Engel, P. hyperplastica Engel, and P. tigris Engel] (Melo 2016; Engel 2022a). A key to the species occurring in Mexico and Central America was provided by Ayala (1999) and for Argentina by Alvarez et al. (2016). Species mostly nest in tree cavities and build brood combs. Two species nest exclusively in internodes in Cecropia Loefl. (Urticaceae), made available by ants, and interact with obligate inquiline scale insects that provide wax and honeydew (Roubik 2021, 2023). A key for the subgenus Nanoplebeia was provided by Engel (2021c).

This genus greatly resembles Tetragona Lepeletier & Audinet-Serville in the presence of yellow maculation on the face and the velvety setation of the gena, the presence of a mesotibial spur, and the plumose setae on the retromarginal edge of the metatibia but can be distinguished by the setose basal area to the propodeum, the calviform metatibia with the proximal third more plump, and the larger mandibular teeth. The bees are 7–9 mm in length and extend from Costa Rica, with a noteworthy gap through Panama, thence to Colombia, central Brazil, and Peru. A key for the species was presented by Camargo (1996) and Camargo and Pedro (2004).

Scaptotrigona is a distinctive group of small to medium-sized bees, 4.5–9 mm, which range in color from orange to black and lack yellow markings except for those on the postgena or elsewhere in one species of the subgenus Sakagamilla Moure [Scaptotrigona affabra (Moure)]. The preoccipital ridge is carinate to minutely lamellate and with three distinctive pits dorsally, and often with an interruption laterally. The metatibiae are also quite characteristic, subtriangular in shape and lacking plumose setae on the retromarginal edge, but bordered by an abundance of rather thick, curved bristles. Like Nannotrigona Cockerell, the mesoscutellum has a characteristic longitudinal depression or groove extending from anterior margin medially, but the integument is not as coarsely punctured. While the genus is easy to distinguish, the species are quite complex with considerable variation and the identification of the species can be difficult. The genus was recently organized into a series of subgenera, including a key to these subgeneric lineages (Engel 2022d). A key to species of the subgenus Sakagamilla is presented in Engel (2022b); to those of Eoscaptotrigona Engel, Gymnotrigona Engel, and Baryorygma Engel in Engel (2022d); to the species of Astegotrigona Engel by Engel (2022e). A partial key to one group of Scaptotrigona s.str. has been published (Engel 2022c) and other new species presented by Engel (2022f), but further work remains to be completed on the Central American fauna (in prep.) as well as Scaptotrigona s.str. in South America. The genus occurs from central Mexico to northern Argentina and is frequently found in meliponiaries. The nest entrance is a long trumpet or tube, sometimes greatly expanded, and usually with small uniformly spaced holes and much flexibility. Species nest almost solely in living trees (except when they live in buildings) and always build regular horizontal combs. A notable exception is S. subobscuripennis (Schwarz), of Costa Rica and western Panama, which nests in cavities in the ground, and apparently never uses tree cavities. The honey has good flavor and is appreciated by many, and propolis from Scaptotrigona is widely used for medicinal purposes. All species have pungent defensive cephalic secretions characterized as 2-nonal and are quite defensive.

This is a genus of small, 4–6 mm long, bees with slightly opaque black integument, without yellow markings, and superficially resemble darker species of Plebeia. The metabasitarsi are large and dilated, wider than the corresponding metatibiae and are used for rubbing floral structures to mop up loosened and scattered pollen. Nests are in tree cavities or even within the arboreal nests of nasutitermitine termites, and the bees build brood combs, except for S. latitarsis (Friese) and the species of Schwarzula Moure who build brood clusters and S. longula (Lepeletier) that builds simple vertical, double-sided appressed cell combs (Oliveira et al. 2013; Nogueira et al. 2023). The species of the subgenus Schwarzula further depart from this biology in that they tend scale insects that have an obligate nesting association and share wax and honeydew (such an association also exists independently in two species of Nanoplebeia: Roubik 2021, 2023). Information on the two species of this subgenus is provided by (Camargo and Pedro 2002a). A key to the species of Scaura s.str. and Scauracea Engel is provided by Nogueira et al. (2019). The genus is found from Veracruz, Mexico to southern Brazil and Bolivia.

This genus includes medium-sized bees, 6–8 mm in length, which were at one time placed among Plebeia. A key to species for the subgenus Schwarziana was provided by Melo (2015), at that time including subgenus Chapadapis Engel. Where known, the bees build nests in the ground, with the brood combs arranged in spirals. The genus is found in central-southern Brazil, and in Paraguay and northern Argentina.

The bees of the genus Tetragona superficially resemble species of Frieseomelitta, as both include relatively long-legged bees, differing mainly by the presence of the mesotibial spur, the velvety pubescence of the gena, the yellow maculation of the head in most species (not extending to the top of the compound eyes and absent on the genae; Tetragona essequiboensis (Schwarz) lacks yellow maculation entirely and species of the handlirschii group only have reddish yellow-brown areas on the clypeus), and the shape of the metatibiae, which are narrower. Species of Tetragona are ~ 5–8 mm in length and occur from Tabasco, Mexico to Uruguay. Species are used in meliponiculture and for supplies of sticky resin materials stored in nests. A key is provided by Nogueira et al. (2022) to species of the clavipes species group.

• T. atahualpa Nogueira & Rasmussen
• T. beebei (Schwarz)
• T. clavipes (Fabricius)
• T. dorsalis (Smith)
• T. essequiboensis (Schwarz)
• T. goettei (Friese)
• T. handlirschii (Friese)
• T. kaieteurensis (Schwarz)
• T. korotaii Nogueira
• T. mayarum (Cockerell)
• T. mourei Nogueira
• T. perangulata (Cockerell)
• T. quadrangula (Lepeletier)
• T. truncata Moure
• T. ziegleri (Friese)

Species of Tetragonisca Moure are small (4–5 mm), slender bees, with yellow maculation on the lower portion of the face in most species, plumose setae on the retromarginal edge of the metatibia, and have a mesotibial spur (resembling Tetragona). However, the species of Tetragonisca have a basal sericeous area (an oval area with matted keirotrichia) on the retrolateral surface of the metabasitarsus of workers and lack velvety pilosity on the gena. The metatibia is also rather inflated, with the corbicula reduced to the apical portion of the podite. The genus extends from Veracruz, Mexico to northern Argentina. It should be noted that the widespread and common Tetragonisca angustula (Latreille) appears to be a complex of species. The systematics of this species should be explored in depth. Nests are built in tree cavities or the ground. No key to species is currently available.

• T. angustula (Latreille)
• T. buchwaldi (Friese)
• T. fiebrigi (Schwarz)
• T. weyrauchi (Schwarz)

This is a genus of enigmatic stingless bees from northern Brazil. The genus includes bees of 5–6 mm in length, and that superficially resemble Frieseomelitta but have conspicuous setae on the compound eyes (hence the generic name). Species of Trichotrigona Camargo & Moure are likely robber bees but seemingly undertaking isolated, rather than mass, raids. Pedro and Cordeiro (2015) provide a means to distinguish the two species.

• T. camargoiana Pedro & Cordeiro
• T. extranea Camargo & Moure

This is a genus with bees of dramatically different proportions, ranging in size from 5–12 mm in length, with plumose setae on the retromarginal edge of the metatibia, velvety pilosity on the gena, a mesotibial spur (resembling Tetragona), and can be reddish orange to black in coloration, but always lack yellow maculation. The mandibles have well-developed, prominent teeth (either four or five). The metatibiae are claviform and in one subgenus (Necrotrigona Engel) the corbicula is not developed. Aside from the raised median keirotrichiate area on the retrolateral surface of the metatibia, there is also a basal sericeous area (an oval area with matted keirotrichia) on retrolateral surface of the metabasitarsus. The biology of Trigona is remarkably varied, perhaps more so than any other genus of Meliponini, and includes obligate necrophages that scavange from carcasses (Necrotrigona). Species nest in squirrel or bird nests as well as in tree cavities, while some nest on the ground among tree roots and others build exposed nests around tree branches. The largest nests are composed of the bees’ own feces, from defecated pollen exines. This group now includes 30 described species but will likely be found to have more than twice as many, like Trigonisca (Rasmussen and Camargo 2008). The subgenus Nostotrigona was revised recently, and a key was provided to the species (Ribeiro et al. 2023).

The genus Trigonisca includes exclusively minute stingless bee species and is the earliest-diverging lineage of extant Neotropical Meliponini. The genus is one of the more widespread groups of New World stingless bees, as well as a relatively commonly encountered group of meliponines. The nesting biology was explored for Trigonisca mepecheu Engel & Gonzalez by Engel et al. (2019). A key to the species of Celetrigona Moure is presented by Camargo and Pedro (2009). The subgenera Leurotrigona and Exochotrigona Engel apparently form a grade at the base of Trigonisca s.l. and are classified by some authors as a separate genus. They can be easily distinguished from the other Neotropical minute bees by the smooth, polished, and shiny integument, the absence of a preoccipital carina, and the absence of yellow markings. Many new species have been encountered and are currently being described for the western Amazon (Roubik 2018). A key to the species was provided by Pedro and Camargo (2009: all species at that time classified in Leurotrigona). A revision of Trigonisca s.str. is needed, but a beginning was made by Albuquerque and Camargo (2007). Camargo and Pedro (2005) provided a key to species for Dolichotrigona, although this group almost assuredly renders Trigonisca s.str. paraphyletic and is therefore not recognized herein. Nonetheless, for readers who prefer to recognize Dolichotrigona we provide the following couplet that distinguishes those species from Trigonisca s.strictiss.

The fauna of stingless bees in Africa and Madagascar is the least diverse of any in the world. Afrotropical Meliponini are unique and found in a line from Senegal to Eritrea along the southern Sahel southward to KwaZulu-Natal, South Africa. The tribe is also found throughout Madagascar. Currently we recognize 33 extant species in the Afrotropical fauna and eight extant genera (Table 2).

Axestotrigona Moure is a genus of modest-sized bees, 5–7 mm in length, and lacking yellow integumental markings. The keirotrichiate zone of the metatibial retrolateral surface extends all the way to retromarginal edge, and therefore is easily distinguished from the genera Meliplebeia Moure and Plebeiella Moure. The brood cells are arranged in horizontal combs and the nests are are built within pre-existing cavities in trees or in the sides of earthen termite nests. A key to the species is provided by Solórzano-Kraemer et al. (2022).

Dactylurina Cockerell is perhaps the most distinctive genus of African stingless bees. As the name implies, the metasoma is elongate, thin, and subclavate, giving it a finger-like shape. The genus occurs from Guinea eastward to the Congo and Uganda and thence southward to Angola. The genus is distinctive for building double vertical combs (e.g., Michener 1974; Njoya et al. 2016), much like Apis Linnaeus, and also shared by the Neotropical Scaura s.str. (Nogueira et al. 2023).

• D. schmidti (Stadelmann)
• D. staudingeri (Gribodo)

Like Liotrigona Moure, Hypotrigona Cockerell includes minute stingless bees commonly encountered in Africa from Senegal eastward to Eritrea, and southward to northern South Africa. The genus is distinctive for the broadly rounded distal superior angle of the metatibia and the dull, matte, reticulate to micro-alveolate integument. The genus is also commonly encountered in East African copal and modern resins (Solórzano-Kraemer et al. 2022). Nest may be built in dry logs, rock or wall crevices, or even in pre-existing cavities of living trees, often with a protruding oval entrance tube. The brood are arranged in clusters or irregular layers (e.g., Portugal-Araújo 1955; Michener 1959; Kajobe 2007; Ndungu et al. 2019).

• H. araujoi (Michener)
• H. gribodoi (Magretti)
• † H. kleineri Engel & Solórzano-Kraemer
• H. ruspolii (Magretti)
• H. squamuligera (Benoist)

This is a genus of minute stingless bees and occurs commonly throughout Madagascar as well as less predominantly on the African continental mainland from Liberia eastward to Ethiopia and southward to the northern half of South Africa. The species can be confused with Hypotrigona but differ in the smooth and shiny integument and the presence of a distinct superior distal angle on the metatibia. The monotypic subgenus Cleptotrigona Moure includes a species that is a robber bee on Hypotrigona and other Liotrigona. A single extinct species is also known from Early Miocene amber from Ethiopia (Engel and Aber 2022). Like most minute stingless bees, the brood cells are clustered rather than arranged in distinct combs (e.g., Brooks and Michener 1988; Hora et al. 2023).

Meliplebeia includes species superficially resembling the smaller Plebeiella and found from Gambia to Eritrea and Somaliland, and southward to Namibia and northern South Africa. Unlike Plebeiella, the basal area of the propodeum is pubescent. Nests are built like those described for Axestotrigona (supra).

The genus Meliponula includes a modestly large and robust species, 6–8 mm in length, found commonly throughout tropical Africa, from Guinea eastward to Kenya and thence southward to Namibia and Botswana. The genus is distinctive for the wholly declivitous propodeal basal area, dull and matte metasomal terga, and restriction of the corbicula to less than the distal half of the metatibia. Nests are constructed within pre-existing cavities in trees, and the brood are arranged in irregular layers (Portugal-Araújo 1955) or can also be within ground cavities. There is a pattern for nests in the highlands to always be belowground, while those of lower elevations are in tree hollows (e.g., Kajobe 2007).

• M. bocandei (Spinola)

The genus Plebeiella includes small bees most similar to Meliplebeia but differing in the glabrous basal area to the propodeum. The genus occurs from Togo eastward to Kenya and southward to Angola and Zambia. Nests are built like those described for Axestotrigona (supra).

• P. griswoldorum (Eardley)
• P. lendliana (Friese)

This genus superficially resembles the New World Plebeia and includes a small species (4–5 mm in length) that can be found from Senegal eastward to Ethiopia and then southward to Angola and northeastern South Africa. Nests are built like those described for Axestotrigona (supra).

• P. armata (Magretti)

The fauna of stingless bees across South and Southeast Asia, through the Indomalayan and Papuasian regions, and into Australia is the richest in the Eastern Hemisphere, with a particularly interesting diversity extending across Indomalaya and Papuasia. A catalogue of the fauna was provided by Rasmussen (2008). All meliponines from these regions belong to the subtribe Hypotrigonina (Table 2), a group which also includes the African lineages as well as likely encompasses those species preserved in European and Asian amber sources (Engel et al. 2021a). Currently we recognize 98 extant species in the fauna and 11 extant genera.

Еxpanded from Rasmussen et al. 2017; Engel and Rasmussen 2017; Engel et al. 2018, 2022; Engel 2019.

Austroplebeia Moure superficially resembles the African Plebeina Moure and the New World Plebeia, particularly in the presence of prominent yellow maculation on the head and mesosoma. The genus occurs in New Guinea southward through northern Australia. A key to the species was provided by Dollin et al. (2015), while a key to the two subgenera was presented by Engel et al. (2021a).

The sole species of this genus of minute bees is found in Southeast Asia and was originally classified in Liotrigona. Recently, however, the discovery of the male demonstrated that the species was more dramatically different from true Liotrigona than originally surmised. Instead, the type species seems more similar to Austroplebeia and was therefore reclassified (Engel et al. 2022). Nests are built in rock crevices and the brood cells are built in irregular clusters (Engel et al. 2022).

• E. carpenteri (Engel)

Geniotrigona Moure includes large robust stingless bees with a prominent elevated ridge on the vertex posterior to the ocelli, a long malar space, and dense plumose setae on the mesosoma. The genus occurs from Southeast Asia through Malesia. A key to the species was provided by Rasmussen et al. (2017).

• G. lacteifasciata (Cameron)
• G. thoracica (Smith)

The genus Heterotrigona Schwarz includes species similar to Homotrigona Moure, but distinctly smaller in size and much reduced mandibular dentition. Three subgenera (Borneotrigona Engel, Heterotrigona s.str., and Sundatrigona Inoue & Sakagami) occur west of the Wallace Line, while the remaining two are found exclusively east of the line. Keys to the species of Platytrigona Moure and Sahulotrigona Engel & Rasmussen were provided by Engel (2019), while a key distinguishing the two species of Sundatrigona was provided by Sakagami et al. (1990).

Homotrigona includes those larger species with pronounced mandibular dentition. Some authors have afforded the individual subgenera generic rank (e.g., Moure 1961). To emphasize the close relationship of these groups we follow a more conservative approach whereby they are considered subgenera of a more inclusive and more readily circumscribed genus. The genus in this concept extends from Southeast Asia through Malesia, but not crossing the Weber Line.

As the generic name implies, the genus is noteworthy for the presence of abundant, short, decumbent, plumose (scale-like) setae covering the mesoscutal surface. Additionally, the integument is generally dull and matte, the basal area of the propodeum is reticulate, and the simple setae of the metatibial retromarginal edge. The metatibia and associated corbicular surface, of some species, is greatly expanded, resulting in a spoon-shaped leg, and often associated with an expanded metabasitarsus [e.g., Lepidotrigona nitidiventris (Smith), L. palavanica (Cockerell), L. latipes (Friese)]. Other species have a more typical metatibia with a smaller corbicular surface, such as L. arcifera (Cockerell), while there are those that have a seemingly intermediary form between the extremes (e.g., L. satun Attasopa & Bänziger). The genus occurs from India eastward to the Philippines and then across Malesia.

• L. amruthae Vikratamath & Thangjam
• L. arcifera (Cockerell)
• L. doipaensis (Schwarz)
• L. flavibasis (Cockerell)
• L. hoozana (Strand)
• L. javanica (Gribodo)
• L. latebalteata (Cameron)
• L. latipes (Friese)
• L. nitidiventris (Smith)
• L. palavanica (Cockerell)
• L. rajithae Vikratamath & Thangjam
• L. satun Attasopa & Bänziger
• L. sikkimensis Vikratamath
• L. terminata (Smith)
• L. thenzawlensis Vikratamath & Thangjam
• L. trochanterica (Cockerell)
• L. ventralis (Smith)