Key to US Monomorium species
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Key to workers of Monomorium known from the United States and Canada. Monomorium inquilinum, Monomorium pergandei and Monomorium talbotae are not included as they lack the worker caste.
1
- Dorsal and posterior faces of propodeum equal in length => 2
- Dorsal face of propodeum shorter than posterior face => 3
- Dorsal face of propodeum longer than posterior face => 4
2
- Mesopleuron punctate; fewer than 8 setae projecting above dorsum of mesosoma => Monomorium cyaneum
 Head of Monomorium cyaneum worker |
 Profile of Monomorium cyaneum worker |
- Mesopleuron not punctate; more than 10 (rarely 8 or 9) setae projecting above dorsum of mesosoma => Monomorium ebeninum
 Head of Monomorium ebeninum worker |
 Profile of Monomorium ebeninum worker |
3
- Fewer than 6 setae projecting above dorsum of mesosoma; occurs in northeastern U. S. => Monomorium emarginatum
 Head of Monomorium emarginatum worker |
 Profile of Monomorium emarginatum worker |
- More than 8 setae projecting above dorsum of mesosoma; occurs in northern Florida => Monomorium trageri
 Head of Monomorium trageri worker |
 Profile of Monomorium trageri worker |
4
- Mesopleuron smooth or nearly so, never punctate => Monomorium minimum
 Head of Monomorium minimum worker |
 Profile of Monomorium minimum worker |
- Mesopleuron punctate or otherwise sculptured => 5
5
- Anterior clypeal margin weakly concave medially, clypeus weakly bicarinate => 6
- Anterior clypeal margin strongly concave medially, clypeus strongly bicarinate => 7
6
- Body uniform yellow with head, mesosoma and anterior section of gaster essentially the same color (posterior section of gaster often dark); petiolar node higher, node narrower, anterior and posterior faces converging only slightly dorsally => Monomorium pharaonis
 Head of Monomorium pharaonis worker |
 Profile of Monomorium pharaonis worker |
- Body strongly bicolored with head and gaster much darker than mesosoma, or occasionally body dark brown and essentially uniformly colored (gaster always uniformly dark); petiolar node lower, node broader, anterior and posterior faces converging more strongly dorsally => Monomorium floricola
 Head of Monomorium floricola worker |
 Profile of Monomorium floricola worker |
7
- Occurs from New Jersey to Florida => Monomorium viridum
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 Profile of Monomorium viridum worker |
- Occurs along California coast => Monomorium ergatogyna
 Head of Monomorium ergatogyna worker |
 Profile of Monomorium ergatogyna worker |
