Key to Monomorium species in or possible in MS and AL (from Creighton 1950 and DuBois 1986) |
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| 1 | The first two of the three segments forming the antennal club subequal in length; workers varying somewhat in size, slightly dimorphic | |
| The three segments of the antennal club successively increasing in length; workers varying very little in size, monomorphic | .....2 (Subgenus Momomorium) |
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| 2(1) | The head and thorax densely punctate, opaque, or feebly shining; the color is a clear reddish yellow (generally found in buildings and not in the wild) | |
| Head and thorax mostly or entirely smooth, strongly shining with only scattered piligerous punctures; color not as above | ...3 |
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| 3(2) | Dorsum of propodeum and propodeal declivity of equal length | |
| Propodeal dorsum and declivity of unequal lengths (either face may be longer) | ....4 |
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| 4(3) | Head and gaster brown, alitrunk, petiole, postpetiole, and appendages dirty yellow | |
| Concolorous dark brown to black or with head greenish brown, alitrunk, petiole, postpetiole, and legs reddish-brown (with green overlay or tint), and gaster black (sometimes with greenish or blueish hues) | ...5 |
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| 5(4) | Length of propodeal dorsum less than length of propodeal declivity | |
| Length of propodeal dorsum greater than length of propodeal declivity | ...6 |
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| 6(5) | The node of the petiole, in profile, about as high as it is long and the anterior peduncle is distinctively shorter than the base of the node; the mesopleurae and the base of the propodeum are mostly smooth and shining; color of worker and queen blackish | |
| The node of the petiole, in profile, is somewhat higher than it is long and the anterior peduncle is about as long as the base of the node; mesopleurae and base of propodeum with rugulae or delicate striae; worker brownish-black, sometimes with strong greenish reflections; queen bicolored, head, alitrunk, waist, and appendages, orangish red and gaster blackish with strong metallic green reflections | ||

