Key to New World Solenopsis Species Complexes

The following key is based on Pacheco, J.A. & Mackay, W.P. 2013. The systematics and biology of the New World thief ants of the genus Solenopsis (Hymenoptera: Formicidae). Edwin Mellen Press, Lewiston, New York. 501 pp. [[Media:Pacheco, J.A. & Mackay, W.P. 2013. The systematics and biology of the New World thief ants of the genus Solenopsis.pdf|PDF]]

Note, the geminata species complex is included for ease of identification and to avoid confusion, as they are commonly found.

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 * Solenopsis

1

 * Second and usually third segment of funiculus at least 1 ~ times as long as broad . . . . . geminata species complex (former subgenus Solenopsis, fire ants and Labauchena)


 * Second and at least third segment of funiculus only slightly longer than broad, usually broader than long (Fig. 5) . . . . . 2

2
return to couplet #1
 * Eyes of worker with at least 12 ommatidia . . . . . 3


 * Eyes of worker with fewer than 12 ommatidia, usually fewer than 6 . . . . . 4

3
return to couplet #2
 * Postpetiole greatly dilated (seen from above), globose . . . . . globularia species complex (former subgenus Euophthalma in part)


 * Postpetiole not greatly dilated, scale-like . . . . . nigella species complex (former subgenus Euophthalma in part)

4
return to couplet #2
 * Clypeus of minor workers usually bicarinate (occasionally lacking carinae) with clypeal carina turning medially from anterior margin of clypeus, anterior clypeal margin of minor worker lacking teeth (major workers with 4 to 5 teeth); female with 10-11 segmented antennae . . . . . wasmannii species complex (former subgenus Diagyne and includes Carebarella bicolor)


 * Clypeus of minor workers bicarinate, carinae diverge anteriorly and always present, clypeal teeth always present, but may be poorly developed; female with II-segmented antenna; widely distributed throughout New World . . . . . 5 (former subgenus Diplorhoptrum, thief ants)

5
return to couplet #4
 * Eye tiny and difficult to see, postpetiole circular viewed dorsally; head elongate and typically coarsely punctured . . . . . pygmaea species complex


 * Eye small, but easily seen (Fig. 7), usually consisting of about 4 (rarely more) ommatidia; without all of the above characteristics . . . . . 6

6
return to couplet #5
 * Scape short (typically less than 0.24 mm), minor segments of funiculus short (about 0.07 mm); petiole thickened as seen in profile. . . . . brevicornis species complex


 * Scape longer (typically longer than 0.24 mm), minor segments of funiculus long (typically> 0.70 mm), if shorter, petiole narrow as seen in profile . . . . . 7

7
return to couplet #6
 * Petiole very wide, apex ofnode forming extensive arch viewed laterally much wider than postpetiole . . . . . stricta'' species complex


 * Petiole approximately as wide as postpetiole (typically slightly wider) than postpetiole, apex of node acute, triangular viewed laterally . . . . . 8

8
return to couplet #7
 * Punctures on dorsum of head usually small, barely perceptible; extralateral clypeal teeth poorly developed; head somewhat elongate (CI 83-85) . . . . . molesta species complex


 * Punctures on head coarse, much wider than hairs arising from them; extralateral teeth typically well developed (at least in majority of nest series); head nearly quadrate (CI 85-92) . . . . . fugax species complex