Identifying workers of the Solenopsis molesta species group in eastern US forests, savannas, and cities
I put together this key based on the features that I have found most reliable for IDing the species listed, thanks to @boingohamster for informing me about the eye proportions of S. nickerson, @aaron567 for alerting me to the shorter funicular segments of S. carolinensis, and the following source for the propodeal shape of S. canariensis (this source is prior to the synonymy of S. abdita and S. canariensis) Thompson, C. R. 1989. The thief ants, Solenopsis molesta group, of Florida (Hymenoptera: Formicidae). Florida Entomologist 72:268-283.
The synonymy was done in Seifert, B. 2026. The tiny Solenopsis ants in greenhouses are two species: S. canariensis Forel and S. carolinensis Forel (Hymenoptera: Formicidae). Contributions to Entomology 76 (1):115-124.
1
1a: Body, anterior of gaster, pale off-white to bright red-orange or yellow-brown....2
1b Body, anterior of gaster, brown to black....6
2 (1a)
2a: Head wider and more square than other species, body, anterior of gaster, pale off-white to light orange, ....S. pergandi (VA south to FL, west to at least forest/plains transition in TX)
2b: Head rectangular....3
3 (2b)
3a: Mesosoma thin, overall more lithe build than other species.... S. zeteki (south edge of FL only)
3b: More normal build for this group....4
4 (3b)
4a: In profile view, dorsal surface of mesosoma more or less convex, with limited distinction between the dorsal and posterior faces of the propodeum....S. canariensis (NC south to FL and west to OK, TX, and nearby parts of Mexico)
4b In profile view, there is a strong bend or angle in separating the dorsal face of the propodeum from the posterior face....5
5 (4b)(7b)
5a: Total length of antenna segments 3-8 is 27% or less of head length....S. carolinensis (MA south to FL west to Pacific)
5b: Total length of antenna segments 3-8 is 27-34% of head length....S. molesta (QC south to FL and west to Pacific)
6(1b)
6a: overall more lithe build and different habitus than other dark members of group....S.picta (NC south to FL and west to forest-plains transition)
6b: Build more typical of this group....7
7(6b)
7a: Eyes noticeably ovoid....S. nickersoni (FL only)
7b: Eyes more circular....5
Range info based on iNat obs and antmaps.org, citations for the latter:
Guénard, B., Weiser, M., Gomez, K., Narula, N., Economo, E.P. (2017) The Global Ant Biodiversity Informatics (GABI) database: a synthesis of ant species geographic distributions. Myrmecological News 24: 83-89.
Janicki, J., Narula, N., Ziegler, M., Guénard, B. Economo, E.P. (2016) Visualizing and interacting with large-volume biodiversity data using client-server web-mapping applications: The design and implementation of antmaps.org. Ecological Informatics 32: 185-193
