Key to Nylanderia clade AC1

Key to Nylanderia clade AC1 species of southern Mexico and Mesoamerica, based on Williams et al. (2025). _NOTOC_

1

Cephalic pubescence moderate to dense (Figs. 4A, 4B); overall color variable => 2
Cephalic pubescence absent to sparse (Fig. 4C); often uniformly yellow with thick, black setae, with specimens from Belize sometimes light to medium brown => Nylanderia cf. docilis

Williams et al. (2025), Fig. 4. Line drawings depicting examples of cephalic pubescence patterns in full-face view: (A) N. austroccidua with uniformly dense cephalic pubescence; (B) N. lazulina with moderate pubescence, concentrated primarily in areas anterior and posterior to the compound eyes; and (C) N. cf. docilis with sparse cephalic pubescence.

Overall color light to dark brown; dense cephalic pubescence (Fig. 4A); scapes relatively short, surpassing posterior margin by no more than a third of their length (SI < 133) => 3
Overall color variable; if overall color is brown or reddish-brown. then cephalic pubescence moderate (Fig. 4B); if overall color is yellow, then cephalic pubescence moderate (Fig. 4B) to dense (Fig. 4A); scape length variable => 6

Williams et al. (2025), Fig. 4. Line drawings depicting examples of cephalic pubescence patterns in full-face view: (A) N. austroccidua with uniformly dense cephalic pubescence; (B) N. lazulina with moderate pubescence, concentrated primarily in areas anterior and posterior to the compound eyes; and (C) N. cf. docilis with sparse cephalic pubescence.

Posterior face of propodeum about as long as or slightly longer than dorsal face; ranging across southern Mexico and Central America => 4
Posterior face of propodeum about twice as long as dorsal face; ranging across southwestern North America from central Mexico to Utah (Fig. 2) => Nylanderia austroccidua

Williams et al. (2025), Fig. 2. Distributions of species: (A) N. austroccidua in the United States and northern Mexico, (B) species found across southern Mexico and Mesoamerica, and (C) N. docilis in South America. Maps were created using GPS coordinates listed in Table S1 and from the Global Ant Biodiversity Informatics (GABI; Guénard et al. 2017) database.

Medium to dark brown with antennae, mandibles, and tarsi yellow in contrast to body; head and gaster concolorous with mesosoma; meso- and metacoxae lighter in color than mesosoma; scapes surpassing posterior margin by about a third of their length (SI ≥ 130) => 5
Light brown with antennae, mandibles, and tarsi concolorous with body; sometimes bicolored with medium brown head and gaster; meso- and metacoxae concolorous with mesosoma; scapes surpassing posterior margin by less than a quarter of their length (SI < 130) => Nylanderia breviscapa

Dark brown, with whitish meso- and metacoxae strongly contrasting with mesosoma; fine cuticular microsculpture resulting in moderate to strong blue iridescence on head and mesosoma => Nylanderia contraria
Medium to dark brown, with meso- and metacoxae somewhat lighter than mesosoma; cuticle smooth and shiny, with no microsculpture and without blue iridescence => Nylanderia polita

Overall color variable, but with head and mesosoma concolorous with gaster; cephalic pubescence dense (Fig. 4A) if overall color is yellow, cephalic pubescence moderate (Fig. 4B) if overall color is brown => 7
Strongly bicolored, with yellow to yellow-brown head and mesosoma and medium to dark brown gaster; cephalic pubescence moderate (Fig. 4B) => Nylanderia mosaica

Williams et al. (2025), Fig. 4. Line drawings depicting examples of cephalic pubescence patterns in full-face view: (A) N. austroccidua with uniformly dense cephalic pubescence; (B) N. lazulina with moderate pubescence, concentrated primarily in areas anterior and posterior to the compound eyes; and (C) N. cf. docilis with sparse cephalic pubescence.

Medium to dark reddish-brown; scapes relatively long, surpassing posterior margin by more than a third to nearly half their length (SI ≥ 140); moderate cephalic pubescence (Fig. 4B); propodeum low and evenly rounded, with posterior face at most slightly longer than dorsal face; found in Guatemala, possibly Honduras => Nylanderia mendax
Color variable; scapes relatively short, surpassing posterior margin by about a quarter to a third of their length (SI < 140); cephalic pubescence moderate (Fig. 4B) in dark specimens and dense (Fig. 4A) in yellow specimens; propodeum high and evenly rounded, with posterior face steep and at most slightly longer than dorsal face; found in Costa Rica => Nylanderia usul

Williams et al. (2025), Fig. 4. Line drawings depicting examples of cephalic pubescence patterns in full-face view: (A) N. austroccidua with uniformly dense cephalic pubescence; (B) N. lazulina with moderate pubescence, concentrated primarily in areas anterior and posterior to the compound eyes; and (C) N. cf. docilis with sparse cephalic pubescence.

Medium to dark reddish-brown; macrosetae relatively thick and black, strongly contrasting in color with body; antennae, mandibles, and tarsi concolorous with body; overall cuticle finely microsculptured, giving matte appearance and strong blue iridescence; erect setae on scapes relatively sparse (SMC < 7); apex of petiole scale without pair of small, erect setae; compound eyes relatively large (REL > 19); scapes relatively long, surpassing posterior margin by nearly half their length (SI ≥ 140); metatibiae relatively long (HTI ≥ 125); mesosoma relatively long (BLI > 146); relatively large in overall size (TL = 1.99–2.52) => Nylanderia lazulina
Light to medium reddish-brown; macrosetae relatively thin and concolorous with body; antennae, mandibles, and tarsi yellow to yellow-brown, contrasting with body; overall cuticle lightly microsculptured and with subtle blue iridescence; erect setae on scapes relatively abundant (SMC ≥ 7); apex of petiole scale bearing a pair of small, erect setae; compound eyes relatively small (REL ≤ 19); scapes relatively short, surpassing posterior margin by less than a quarter of their length (SI < 130); metatibiae relatively short (HTI < 115); mesosoma relatively short (BLI ≤ 146); relatively small in overall size (TL = 1.71–2.24) => Nylanderia luceata