Key to Monomorium workers of the New World

This key is based on: DuBois, M. B. 1986. A revision of the native New World species of the ant genus Monomorium (minimum group) (Hymenoptera: Formicidae). University of Kansas Science Bulletin. 53:65-119.

The following species are not included in this key and apparently lack a worker caste: Monomorium inquilinum, Monomorium pergandei, and Monomorium talbotae.

1

 * Propodeum rounded; occurs along California coast . . . . . Monomorium ergatogyna


 * Propodeum angular . . . . . 2

2
return to couplet #1
 * Basal and declivitous faces of propodeum of equal length . . . . . 3


 * Basal and declivitous faces of propodeum of unequal length (either face may be longer) . . . . . 5

3
return to couplet #2
 * Mesopleuron punctate; fewer than 8 setae projecting above dorsum of alitrunk; occurs throughout central Mexico, Arizona, New Mexico, and parts of Texas . . . . . Monomorium cyaneum


 * Mesopleuron not punctate; more than 10 (rarely 8 or 9) setae projecting above dorsum of alitrunk . . . . . 4

4
return to couplet #3
 * Petiole and postpetiole convex to flat; occurs in central Mexico . . . . . Monomorium compressum


 * Petiole and postpetiole flat to slightly emarginate; occurs throughout Caribbean region . . . . . Monomorium ebeninum

5
return to couplet #3
 * Basal face of propodeum length less than declivity . . . . . 6


 * Basal face of propodeum length greater than declivity . . . . . 7

6
return to couplet #5
 * Fewer than 6 setae projecting above dorsum of alitrunk; occurs in northeastern U. S. . . . . . Monomorium emarginatum


 * More than 8 setae projecting above dorsum of alitrunk; occurs in northern Florida . . . . . Monomorium trageri

7
return to couplet #5
 * Mesopleuron punctate; occurs along Atlantic coastline from New Jersey to Florida . . . . . Monomorium viridum


 * Mesopleuron not punctate (for further separation of these species refer to their distributions) . . . . . Monomorium minimum . . . . . Monomorium wheelerorum . . . . . Monomorium marjoriae