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

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

Head of Monomorium viridum worker
Profile of Monomorium viridum worker
Head of Monomorium ergatogyna worker
Profile of Monomorium ergatogyna worker