Key to New World Solenopsis Species Complexes

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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. 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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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 fewer than 12 ommatidia, usually fewer than 6 . . . . . 4

3

return to couplet #2

  • 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 of node 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