Classification

- Andrenidae (Latreille, 1802) [Family]
- Apidae (Latreille, 1802) [Family]
- Colletidae (Lepeletier, 1841) [Family]
- Halictidae (Thomson, 1869) [Family]
- Megachilidae (Latreille, 1802) [Family]
- Melittidae (Michener, 2000) [Family]
- Stenotritidae (Michener, 2000) [Family]

Keys

• Key to the families, based on adults (Michener, 2007)
  
  
  • 1 (1)
    - Labial palpus with first two segments elongate (Fig. 33-1a), flattened, the last two segments small, usually diverging laterally from axis of first two, not flattened, rarely absent; galeal comb absent or rarely weakly indicated; stipital comb and concavity commonly present (Figs. 19-1a, 33-1b); galeal blade elongate, commonly as long as or longer than stipes (Fig. 33-1a); volsella frequently absent or difficult to recognize, rarely with distinct digitus and cuspis [L-T (long-tongued) bees] ↦ 2
    
    
  - Labial palpus with the four segments similar to one another (Fig. 33-1c), or first or rarely first two elongate but not much flattened; galeal comb commonly present; stipital comb and concavity absent (Fig. 33-1d); galeal blade usually shorter than stipes (Fig. 33-1d); volsella commonly well developed, usually with recognizable digitus and cuspis [S-T (short-tongued) bees ↦ 3
  
  
  
  • 2 (1)
    - Labrum with basolateral angles enlarged, base forming broad articulation with clypeus, labrum thus widest at base (Fig. 33-2a); labrum at least 0.8 times as long as broad and usually as long as broad or longer; forewing with two submarginal cells, usually about equal in length (except with three in Fideliini); scopa, when present, restricted to metasomal sterna ↦ Megachilidae
    
    
  - Labrum with basolateral angles little developed, articulation with clypeus thus narrower than full width of labrum (Fig. 33-2b); labrum usually broader than long, but in some parasitic forms (where scopa is absent) labrum elongate; forewing with two or three submarginal cells, rarely only one; scopa, when present, on hind leg, particularly the tibia, and usually absent on metasomal sterna ↦ Apidae
  
  
  
  • 3 (1)
    - Glossa pointed at apex, sometimes with flabellum ↦ 4
    
    
  - Glossa bluntly rounded, truncate, or bilobed at apex (except pointed in males of three hylaeine genera from Australia-New Guinea area); flabellum absent ↦ 7
  
  
  
  • 4 (3)
    - Lacinia represented by scalelike lobe with hairs near base of galea (Fig. 33-1b, d); mentum and lorum forming proboscidial lobe (Figs. 33-3b-f, 33-4b), both at least partly sclerotized; lorum not flat ↦ 5
    
    
  - Lacinia inconspicuous or displaced, not a scalelike lobe at base of galea (Fig. 21-2a, b, b); mentum and lorum not forming proboscidial lobe (Figs. 33-3h, i, 34-4a), mentum sometimes membranous; lorum membranous or nearly flat sclerotized membrane (apron) between cardines (Figs. 33-3h, 34-4a) ↦ 7
  
  
  
  • 5 (4)
    - Lorum more or less platelike but produced in middle for attachment to base of mentum; facial fovea present in females (Fig. 33-2c) and some males, fovea sometimes a groove rather than broad as in figure; subantennal area almost always defined by two subantennal sutures below each antennal socket (Fig. 33-2c) ↦ Andrenidae
    
    
  - Lorum slender, V-shaped or Y-shaped, as in L-T bees (Fig. 33-1a); facial fovea absent; a single subantennal suture below each antennal socket (as in Fig. 33-2d) ↦ Melittidae
  
  
  
  • 6 (4)
    - Lacinia a small, hairless sclerite hidden between expanded stipites; subantennal area defined by two subantennal sutures below each antennal socket (as in Fig. 33-2c); stigma nearly absent; first flagellar segment as long as scape or longer ↦ Andrenidae
    
    
  - Lacinia represented by small, hairy lobe on anterior surface of labiomaxillary tube above rest of maxilla (Fig. 21-2a); a single subantennal suture below each antennal socket (Fig. 33-2d); stigma well developed; first flagellar segment much shorter than scape ↦ Halictidae
  
  
  
  • 7 (3)
    - Apex of glossa bluntly rounded, without preapical fringe or apical glossal lobes; episternal groove absent below scrobal groove; scopa present on hind tibia, but absent on femur ↦ Stenotritidae
    
    
  - Apex of glossa truncate to bilobed (except pointed in males of three genera in Australia-New Guinea region); episternal groove usually present below scrobal groove; scopa, when present, well developed on hind femur as well as tibia ↦ Colletidae
  
  
• Practical Key to Family-Group Taxa, Based on Females (Michener, 2007z)
  
  
  • 1 (1)
    - Scopa, consisting of hairs for carrying pollen, present (Figs. 6-4, 8-5b, 8-7b, 10-11a) ↦ 2
    
    
  - Scopa absent (Figs. 8-5a, 8-7b, 8-8a) ↦ 18
  
  
  
  • 2 (1)
    - Scopa consisting of erect branched hairs, longest on S2, shorter on S1 and S3 (Fig. 46-1b), scopal hairs often present also on hind legs [body hylaeiform; submarginal cells two, second much smaller than first (Fig. 46-1)] neotropics) ↦ Xeromelissinae
    
    
  - Scopa variable, but hairs not erect, not longest, and branched on S2 ↦ 3
  
  
  
  • 3 (2)
    - Scopa well developed on metasomal sterna (Fig. 8-7b) but absent on hind legs [submarginal cells two, usually about equal in length (Figs. 76-1a, 80-1, 81-1, 82-1, 83-2, 84-1), except three in Fideliini, which have long hairs on hind legs that are not used in carrying pollen] ↦ Megachilidae
    
    
  - Scopa on hind legs (Figs. 6-4, 8-5b, 10-11a), sometimes also on sterna ↦ 4
  
  
  
  • 4 (3)
    - Scopa (sometimes as a tibial corbicula) on hind tibia and usually basitarsus, elsewhere not well developed, tibial scopa thus looking considerably larger than that of femur (Figs. 6-4, 10-11a) ↦ 5
    
    
  - Scopa on hind femur (Fig. 8-5b), where a ventral corcorbicula is usually evident, scopal hairs usually also present on trochanter, tibia, and basitarsus and sometimes on metasomal sterna ↦ 12
  
  
  
  • 5 (4)
    - Facial fovea rather small but well defined (Fig. 59-1); two subantennal sutures well separated on clypeal margin below each antenna (Fig. 33-2c) [apex of marginal cell truncate or sometimes obliquely cut off (Figs. 50-1f, 53-1, 53-2, 54-1, 56-1, 58-1, 58-2, 59-2) and thus pointed, but apex well separated from wing margin] ↦ 6
    
    
  - Facial fovea absent or vaguely defined; one subantennal suture below each antenna (Fig. 33-2d) or if two, then the two nearly meeting on clypeal margin ↦ 7
  
  
  
  • 6 (5)
    - Facial fovea deep, with conspicuous hairs (Fig. 50-1a, b) (Peru) ↦ Alocandreninae
    
    
  - Facial fovea shallow, hairless, shining ↦ Panurginae
  
  
  
  • 7 (5)
    - Two subantennal sutures below each antenna, the two nearly meeting at clypeal margin (Chile) ↦ Andreninae
    
    
  - One subantennal suture below each antenna (Fig. 33-2d) ↦ 8
  
  
  
  • 8 (7)
    - Body largely yellow; labrum with basolateral angles strongly developed, thus broadest at extreme base where articulated to clypeus (as in Fig. 33-2); subantennal suture short, directed toward outer margin of antennal socket (pygidial and prepygidial fimbriae absent) (Palearctic deserts) ↦ Pararhophitini
    
    
  - Body usually exhibiting little or no yellow; labrum with basolateral angles little developed, thus not broadest at extreme base and articulation with clypeus shorter (as in Fig. 33-2b); subantennal suture usually directed toward middle or inner margins of antennal socket ↦ 9
  
  
  
  • 9 (8)
    - Episternal groove extending below scrobal groove (as in Fig. 20-5b) although frequently shallow (antennae arising below middle of face) ↦ Rophitinae
    
    
  - Episternal groove not extending below scrobal groove (Fig. 20-5a, c) ↦ 10
  
  
  
  • 10 (9)
    - Glossa short, apex broadly rounded (inner hind tibial spur pectinate) (Australia) ↦ Stenotritidae
    
    
  - Glossa pointed, often with flabellum ↦ 11
  
  
  
  • 11 (10)
    - L-T bees, first two segments of labial palpus elongate, flattened (Figs. 10-4a, 19-1b); episternal groove commonly present down to or curving into and joining scrobal groove (Fig. 20-5c) ↦ Apidae
    
    
  - S-T bees, first two segments of labial palpus similar in form to subsequent segments (Figs. 10-4c, 19-5b); episternal groove almost completely absent ↦ Melittidae
  
  
  
  • 12 (4)
    - Facial fovea well developed, covered with short hairs (two subantennal sutures below each antenna, often difficult to see) (Fig. 33-2c) ↦ Andreninae
    
    
  - Facial fovea absent or not well defined, not bearing distinctive short hairs, but if defined, then bare ↦ 13
  
  
  
  • 13 (12)
    - Stigma absent (Fig. 60-2a); two subantennal sutures below each antenna (as in Fig. 51-1a) (Western Hemisphere) ↦ Oxaeinae
    
    
  - Stigma present, although sometimes no wider than prestigma as measured to wing margin; ordinarily only one subantennal suture below each antenna (Fig. 33-2d) ↦ 14
  
  
  
  • 14 (13)
    - Stigma almost always shorter than prestigma, vein r arising almost at its apex, margin of stigma in marginal cell concave or straight and not much longer than width of stigma (Fig. 43-1); large, robust, euceriform, hairy bees (Western Hemisphere) ↦ Diphaglossinae
    
    
  - Stigma longer than prestigma, vein r arising near its middle or at least well before its apex, margin of stigma in marginal cell straight or convex, much longer than width of stigma; andreniform bees, much more slender than those of above alternative ↦ 15
  
  
  
  • 15 (14)
    - Episternal groove extending little below scrobal groove ↦ Nomiinae
    
    
  - Episternal groove extending far below scrobal groove (Fig. 20-5b), commonly onto venter of thorax ↦ 16
  
  
  
  • 16 (15)
    - Basal vein only feebly arcuate (Fig. 39-5); glossa bilobed (Fig. 19-2a, b) ↦ Colletinae
    
    
  - Basal vein strongly curved (Fig. 65-5); glossa acutely pointed (Figs. 19-2c, d, 28-1a-c) ↦ 17
  
  
  
  • 17 (16)
    - T5 with prepygidial fimbria divided by medial longitudinal zone or triangle of short, dense hairs (Fig. 65-1j) and minute, dense punctations (the hairs sometimes absent) ↦ Halictinae
    
    
  - T5 with prepygidial fimbria weak but continuous (Eastern Hemisphere) ↦ Nomioidinae
  
  
  
  • 18 (1)
    - Episternal groove extending far below scrobal groove (Fig. 20-5b) toward ventral surface of thorax (S6 exposed, not bifurcate) ↦ 19
    
    
  - Episternal groove absent or curving into scrobal groove (Fig. 20-5a, c), extending below scrobal groove only in Caenoprosopidini (in which S6 is retracted, only its bifurcate apex exposed) ↦ 21
  
  
  
  • 19 (18)
    - Glossa pointed (Fig. 19-2c, d); basal vein strongly curved (Fig. 65-5); submarginal cells usually three ↦ Halictinae
    
    
  - Glossa bilobed or broadly truncate (Fig. 19-2a, b); basal vein gently arcuate (Fig. 39-5); submarginal cells two, second usually much smaller than first (Figs. 47-2, 48-2, 48-3) ↦ 20
  
  
  
  • 20 (19)
    - Supraclypeal area elevated abruptly above level of antennal sockets (Fig. 47-3a); pygidial plate usually absent, but if present, then broad, its margins converging posteriorly; anterior surface of T1 usually lacking longitudinal median groove ↦ Hylaeinae
    
    
  - Supraclypeal area sloping up from level of antennal sockets; pygidial plate present, the apical part slender, parallel-sided or spatulate; anterior surface of T1 with longitudinal median groove ↦ Euryglossinae
  
  
  
  • 21 (18)
    - S6 retracted under S5 except for apex, metasomal venter thus appearing to be five-segmented; apex of S6 bilobed, bifurcate, or produced to median spine, frequently bearing rows or clumps of stiff setae (Fig. 91-2) ↦ Nomadinae
    
    
  - S6 more fully exposed, the metasomal venter thus recognizably six-segmented; apex of S6 not modified as above ↦ 22
  
  
  
  • 22 (21)
    - Labrum with basolateral angles strongly developed, labrum thus broad at extreme base, where articulated to clypeus (Fig. 33-2a); labral shape more or less rectangular and usually longer than broad (forewing with two submarginal cells) ↦ Megachilinae
    
    
  - Labrum with basolateral angles weakly developed, labrum thus not broadest at extreme base, articulation with clypeus not extending full width of labrum (Fig. 33-2b); labral shape often less rectangular, often rounded apically, usually broader than long ↦ 23
  
  
  
  • 23 (22)
    - Epistomal suture between lateral extremity and subantennal suture arcuate, upper part of clypeus thus almost parallel-sided (Fig. 90-2); submarginal cells two (Eastern Hemisphere) ↦ Allodapini
    
    
  - Epistomal suture not arcuate upward in such a way that upper part of clypeus is almost parallel-sided; submarginal cells usually three ↦ Apinae