1	A. Forewing venation greatly reduced; RS absent and crossvein r present only as a short stub; Neotropical, rare.	Mesocoelus
–	B. Forewing venation moderately reduced; apical abscissa of RS absent, or mostly so, but crossvein r complete to junction of RS; Neotropical, rare.	2
–	C. Forewing venation not significantly reduced; apical abscissa of RS complete or almost complete to wing margin; widespread, common.	4
2(1)	A. Hind wing subbasal (SB) cell 4-sided with vein Cub emanating from an angle in the cell AND/OR AA. Posterior surface of scutellum with a semi-circular or arc-shaped depression (post-scutellar depression)	Therophilus (in part)
–	B. Hind wing subbasal (SB) cell 3-sided. If Cub vein is present, it emanates from a straight vein. BB. Post scutellar depression absent, but rugose sculpture usually present.	3
3(2)	A. Median area of first tergum not raised above lateral portions and granulate or striogranulate. AA. Hind coxal cavities (HCC) open to metasomal foramen or narrowly closed and positioned partly above ventral margin of metasomal foramen (MF); ventral margin of metasomal foramen lacking a straight transverse carina	Plesiocoelus
–	B. Median area of first tergum raised above lateral portions, sculpture variable but often smooth or smoothly striate. BB. Hind coxal cavities closed and positioned completely below the metasomal foramen; ventral margin of metasomal foramen with a strong, relatively straight transverse carina (TC)	Aerophilus (in part)
4(1)	A. Fore tarsal claws bifid	5
–	B. Fore tarsal claws simple, with distinct basal lobe.	9
–	C. Fore tarsal claws simple, lacking a distinct basal lobe.	31
5	A. Forewing areolet quadrate, not or only slightly narrower anteriorly. AA. Ovipositor as long as or longer than half the length of metasoma	7
–	B. Forewing areolet triangular, or if quadrate much narrower anteriorly. BB. Ovipositor shorter than half the length of metasoma.	6
6(5)	A. Gena expanded into a flange posteriorly; malar space (MS) more than ½ length of eye height (EH); Neotropical, rare	Hemichoma
–	B. Gena not modified into a flange posteriorly; malar space (MS) less than ½ length of eye height (EH); widespread, common	Zelomorpha
7(5)	A. Body predominantly orange/yellow. AA. Frons bordered by a carina posteriorly; widespread, common	8
–	B. Body predominantly black. BB. Frons not bordered by a carina posteriorly; southern USA through the tropical Neotropics, uncommon	Zacremnops
8(7)	A. Propodeum and hind coxa with granulate sculpture; first metasomal tergum ca. 3 × wider at apex than at base; rare; Neotropical, rare	Labagathis
–	B. Propodeum and hind coxa lacking granulate sculpture; first metasomal tergum not ca. 2 × wider at apex than at base; widespread, relatively common	Cremnops
9(4)	A. Notauli present	10
–	B. Notauli absent	25
10(9)	A. Ventral margin of clypeus projecting; width of temple longer than width of eye in lateral view; Nearctic, rare	Gelastagathis
–	B. Ventral margin of clypeus not projecting; width of temple shorter than width of eye in lateral view; widespread, common	11
11(10)	A. Frons bordered by carinae or grooves posteriorly.	12
–	B. Frons not bordered by carinae or grooves posteriorly.	14
12(11)	A. Hind coxa with granulate sculpture. AA. Second submarginal cell minute or absent; Neotropical, rare	Trachagathis
–	B. Hind coxa smooth, lacking granulate sculpture. BB. Second submarginal cell of normal dimensions; widespread, common.	13
13(12)	A. First metasomal tergum smooth with two widely spaced converging carinae forming a teardrop-shaped basal area; Neotropical, rare	Pharpa
–	B. First metasomal tergum usually smooth and convex, or BB. With a median longitudinal carina, or, BBB. Rarely with 2 carinae, in which case the tergum has more extensive sculpture; widespread, common	Alabagrus
14(11)	A. Malar space (MS) distinctly greater than ½ eye height (EH); head shape in frontal view elongate, at least as high (measured from ventral margin of clypeus) as wide.	15
–	B. Malar space USUALLY (95%) equal to or less than ½ eye height; head shape in frontal view wide, wider than high (measured from ventral margin of clypeus)	16
15(14)	A. Third tergum completely smooth; pair of carinae on first tergum not prominent. AA. Hind coxal cavities (HCC) open to metasomal foramen or narrowly closed and positioned partly above ventral margin of metasomal foramen (MF); common in Nearctic, very rare in Neotropics	Agathis (in part)
–	B. Third tergum usually (95%) partly or completely sculptured, sculpture often confined to narrow line along transverse depression; pair of carinae on first tergum prominent. BB. Hind coxal cavities closed and positioned completely below the metasomal foramen; ventral margin of metasomal foramen with a strong, relatively straight transverse carina (TC); widespread, common	Aerophilus (in part)
16(14)	A. Propodeal spiracle elongate, more than 2 × longer than wide; widespread, common	Pneumagathis
–	B. Propodeal spiracle circular or ovoid, not more than 2 × longer than wide	17
17(16)	A. Pair of carinae on first tergum NOT prominent. AA. Hind coxal cavities (HCC) open to metasomal foramen or narrowly closed and positioned partly above ventral margin of metasomal foramen (MF).	18
–	B. Pair of carinae on first tergum prominent; BB. Hind coxal cavities closed and positioned below the metasomal foramen; ventral margin of metasomal foramen with a strong, relatively straight transverse carina (TC); widespread, common	Aerophilus (in part)
18(17)	A. First tergum completely smooth, or rarely with some punctures posterolaterally	20
–	B. First tergum with sculpture	19
19(18)	A. Vein Cub of hind wing long and partly tubular, apical margin of subbasal (SB) cell angled; widespread, common.	Therophilus (in part)
–	B. Vein Cub of hind wing weak or absent and never tubular; apical margin of subbasal cell (SB) straight. Nearctic and northern Neotropics (i.e., Mexico and Central America), much less common	Agathirsia (in part)
20(18)	A. Notauli pitted or crenulate	21
–	B. Notauli smooth	24
21(20)	A. Third tergum usually entirely smooth or weakly and partly coriarious (leather-like), if with different sculpture (especially in transverse depressions), then pair of longitudinal carinae on first metasomal tergum weaker than in B or absent. AA. Hind coxal cavities (HCC) open to metasomal foramen or narrowly closed and positioned partly above ventral margin of metasomal foramen (MF)	22
–	B. Third tergum usually partly or completely sculptured, sculpture often confined to narrow line along transverse depression; pair of longitudinal carinae on first metasomal tergum present and extending past spiracles. BB. Hind coxal cavities closed and positioned entirely below the metasomal foramen (MF); ventral margin of metasomal foramen with a strong, relatively straight transverse carina (TC); widespread, common	Aerophilus (in part).
22(21)	A. First tergum partly or completely granulate; widespread, common	Neothlipsis
–	B. First tergum otherwise sculptured, usually striate or rugostriate.	23
23(22)	A. Posterior apex of scutellum with a distinct depression in the form of a semicircle or two distinct pits; widespread, common.	Therophilus (in part)
–	B. Posterior apex of scutellum lacking depression, smooth to rugose; common in Nearctic, very rare in Neotropics.	Agathis (in part)
24(20)	A. Propleuron with a distinct protuberance; gena expanded into an acute angle posteroventrally; Neotropical, rare	Zamicrodus
–	B. Propleuron flat or weakly convex, lacking a distinct protuberance; genae not expanded and rounded posteroventrally; Neotropical, rare	Aphelagathis
25(9)	A. Second submarginal cell of forewing quadrate. AA. Cub vein of hind wing present and often tubular; subbasal cell angled distally at junction of Cub; Chile and southern Argentina (Note: Unlike the better known north temperate group of Earinus, members of this assemblage are found only in southern and high-altitude South America, and may deserve separate generic status), common	Earinus (in part)
–	B. Not combining the above character states; second submarginal cell usually triangular. BB. Cub vein of hind wing usually absent or not tubular, and subbasal sell not angled distally.	26
26(25)	A. Forewing vein RS+M present and complete, though sometimes weaker at midlength; Nearctic, common.	Earinus (in part)
–	B. Forewing vein RS+M completely or mostly absent	27
27(26)	A. Third tergum completely smooth. AA. Hind coxal cavities (HCC) open to metasomal foramen (MF), or narrowly closed such that the ventral part of the metasomal foramen is below the dorsal margin of the hind coxal cavities	28
–	B. Third tergum usually (95% of specimens) partly or completely sculptured, sculpture often confined to narrow lines along transverse depressions. BB. Hind coxal cavities closed and positioned completely below the metasomal foramen; ventral margin of metasomal foramen with a strong, relatively straight transverse carina; widespread, common	Aerophilus (in part)
28(27)	A. Spurious vein, RS2b, well-developed. AA. Ovipositor barely exerted, much shorter than metasoma. Neotropical, very rare	Marjoriella
–	B. Spurious vein, RS2b, lacking. BB. Ovipositor at least as long as metasoma. Widespread, common	29
29(28)	A. Second submarginal cell smaller than its dorsal stem; apical abscissa of RS curving towards fore margin of wing; Neotropical, very rare	Smithagathis
–	B. Second submarginal cell larger than its dorsal stem; apical abscissa of RS straight	30
30(29)	A. Posterolateral corner of gena sharp; propleuron with a protuberance; Neotropical, rare	Amputoearinus
–	B. Posterolateral corner of gena rounded; propleuron evenly convex, lacking a protuberance; widespread, common.	Lytopylus
31(4)	A. Notauli absent, mesoscutum completely smooth; Neotropical, rare	Sesioctonus
–	B. Notauli present though sometimes only indicated anteriorly or posteriorly; widespread and common in Nearctic, rare in Neotropics.	32
32(31)	A. First tergum smooth, lacking microsculpture, at most with punctures laterally; Nearctic and Central America, rare	33
–	B. First tergum with microsculpture, usually in the form of longitudinal striae or rugae; widespread and common in Nearctic, extremely rare in Neotropics	Agathis (in part)
33(32)	A. Ovipositor barely exerted, shorter than half the length of metasoma; Nearctic and Central America (all species of Crassomicrodus key here)	Crassomicrodus
–	B. Ovipositor at least as long as half the metasoma, often much longer; Nearctic and Central America, rare (few species key here)	Agathirsia (in part)