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Key to species of Pseudomyrmex workers (except P. leptosus of which worker is unknown) in the southeastern United States

(from Ward 1985)

(definitions of measurements and indices )
1  Erect hairs present and conspicuous on most parts of body, including mesonotum and propodeum
...2
  Erect hairs very sparse, lacking on mesonotum and usually lacking on propodeum
...4
2(1)  Large species with head about as wide as long (HW > 1.40, CI > 0.95); color bicolored orange and black; petiole with a long anterior peduncle
  Small species with head longer than wide (HW < 0.80, CI < 0.80); color is a uniform brown; the petiole short and without a long anterior peduncle
...3
3(2)   Larger species (HW 0.64 mm or greater), shorter eyes with REL2 0.63 -0.73 and with lower thinner petiole
  Smaller species (HW 0.64 mm or less), longer eyes (REL2 0.73 - 0.82), and higher, broader petiole
4(1)  The head and gaster usually dark brown; small species (HW < 0.82);  metanotal groove deep and wide; the dorsal face of the propodeum usually shorter than declivity (anything formerly identified as P. brunneus (F.Smith) is probably P. ejectus.  P. brunneus is not found in the US.
  The head and gaster golden yellow to orange-brown in color; size variable; metanotal groove generally relatively shallow but if groove is deep then the dorsal face of propodeum is obviously longer than the declivity
...5
5(4) First gastral tergite smooth and shining, mostly lacking appressed pubescence; vertex of head smooth and shining; small species (HW 0.55 - 0.74) (only known in the US from FL)
  First gastral tergite subopaque, with mat of fine appressed pubescence; vertex of head weakly shining to subopaque; larger species (HW 0.68 - 1.04)
6
6(5) Larger species (HW 0.87-0.96); the frontal carinae well separated; the eyes are shorter (EL 0.43-0.48); the median part of the anterior clypeal margin is weakly angulate, appearing tridentate
  Smaller species (HW 0.68-0.89); the frontal carinae not well separated, almost contiguous; eyes longer (EL 0.45-0.54); median part of anterior clypeal margin generally straight
Key to queens
1  Large species (HW > 1.45); bicolored black and orange; erect hairs abundant on most of body including propodeum; petiole with long anterior peduncle;
  Smaller species (HW < 1.10); not bicolored black and orange, but brown or golden yellow; either petiole very short and without obvious peduncle or erect hairs sparse and lacking on propodeum
...2
2(1)      The head with dense punctation; head more than 1.5 times as long as wide (CI 0.57-0.64); petiole short; some erect hairs on propodeum (usually) .
...3
  The head varies from being finely punctate to smooth and shining; head usually less than 1.5 times as long as wide (CI 0.66-0.86); petiole relatively long; propodeum lacking erect hairs
...4
3(2) Larger species (HW 0.65 - 0.72); eye length less than one half head length; petiole moderately long
  Smaller (HW 0.56 - 0.58); eye length about one half head length; petiole short
4(2)  The head and gaster usually dark brown; smaller species (HW 0.62-0.75); the frontal carinae are closely contiguous; the petiole long and slender and more than twice as long as high
  The head and gaster golden yellow to orange-brown; size either larger or smaller (HW 0.57-1.03), but if smaller (HW <0.80) then the petiole is shorter
...4
5(4) First gastral tergite smooth and shining, mostly lacking appressed pubescence; vertex of head smooth and shining; small species (HW 0.57 - 0.75) (only known in the US from FL)
  First gastral tergite subopaque, with mat of fine appressed pubescence; vertex of head weakly shining to subopaque; larger species (HW 0.66 - 1.03)
...6
6(5)  Large species (HW 0.85-1.03, HL 1.28-1.46); frontal carinae well separated; eyes short (EL 0.52-0.58)
  Smaller species (HW 0.66-0.92, HL 0.82-1.15); frontal carinae more closely contiguous; eyes longer (EL 0.59-0.71)
...6
7(6)     Head, especially upper half, smooth, shining, with scattered fine punctures; occipital margin broadly rounded; small species (HW 0.67 0.70 mm)
  Head coriaceous, only weakly shining, punctures coarser; lateral margins of occiput more sharply rounded; larger species (HW 0.66 - 0.92 mm