Key to Solenopsis pygmaea species complex

The following 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]]

The pygmaea species complex is a group of New World thief ants in the genus Solenopsis.

1

 * Very hairy, with more than 20 erect and suberect hairs on outline of pronotum (as seen with mesosoma in lateral view) . . . . . 2


 * Hairs absent or with not more than 10 erect and suberect hairs on outline of pronotum (in lateral view of mesosoma) . . . . . 7

2
return to couplet #1
 * Pronotal hairs of various lengths (0.03-0.05 mm), minor funicular segments (3-8) 0.07 -0.09 mm in total length . . . . . 3


 * Pronotal hairs all short and approximately of same length (mostly less than 0.03 mm), minor funicular segments (3-8) 0.07 mm or less in total length . . . . . 6

3
return to couplet #2
 * Relatively few erect and suberect hairs on first gastral tergum (fewer than 20) of various lengths, up to 0.05 mm . . . . . 4


 * First gastral tergum with abundant fine, short hairs (up to 0.04 mm, most less than 0.03 mm) all approximately same length . . . . . 5

4
return to couplet #3
 * Smaller (total length typically less than 1.3 mm); southern USA south into Mexico . . . . . Solenopsis tennesseensis


 * Larger (total length at least 1.3 mm); southeastern Brazil . . . . . Solenopsis goeldii

5
return to couplet #3
 * Head thicker viewed laterally (0.25 mm from dorsal to ventral surface); total length 1.4-1.7 mm; head length 0.39-0.40 mm; head width 0.31-0.35 mm; petiolar peduncle with small ventral tooth; USA (Florida and Texas) . . . . . Solenopsis tonsa


 * Head thinner viewed laterally (less than 0.25 mm from dorsal to ventral surface); total length 0.9-1.0 mm; head length 0.34-0.36 mm; head width 0.24-0.28 mm; petiolar peduncle lacking ventral tooth; Caribbean Islands and eastern Mexico and Guatemala . . . . . Solenopsis pygmaea

6
return to couplet #2
 * Head thinner, 0.18 mm from dorsal to ventral surface); length of minor segments of funiculus ~0.06 mm in length; USA (Louisiana and Texas) to Colombia (Cauca) and Venezuela (Distrito Federal) . . . . . Solenopsis subterranea


 * Head thicker (0.24 mm from dorsal to ventral surface); length of minor segments of funiculus 0.8 mm in length; Trinidad, Guianas, Argentina (Buenos Aires, Tucuman) . . . . . Solenopsis minutissima

7
return to couplet #1
 * Eyes poorly defined or nearly absent . . . . . 8


 * Eyes present, with at least one ommatidium (rarely 2) . . . . . 9

8
return to couplet #7
 * Pronotum without hair; total length 1.3 mm; cuticle unpolished, translucent (milky appearance); head width 0.30-0.33 mm; central Texas . . . . . Solenopsis impolita


 * Pronotum with more than 4 hairs; widely distributed . . . . . 10

9
return to couplet #7
 * Dorsum offirst gastral tergum with more than 40 erect or suberect hairs approximately equal in length (about 0.02 mm); central-eastern Mexico . . . . . Solenopsis isopilis
 * Dorsum of first gastral tergum with fewer than 40 erect or suberect hairs of various lengths (many over 0.05 mm); USA (southern New Mexico and Louisiana) . . . . . 11

10
return to couplet #8
 * USA (southern New Mexico), head greatly elongate, ~0.4 mm in length . . . . . Solenopsis pulleni


 * Widely distributed, Argentina; Chile; Guianas; Trinidad; and Mexico; head not greatly elongated . . . . . 12

11
return to couplet #10
 * Head longer (HL 0.38-0.41 mm); scape relatively longer (SL 0.23-0.26 mm, SI 59-63); Arizona and Louisiana . . . . . Solenopsis ocellata


 * Head shorter (HL 0.35-0.36 mm); scape relatively shorter (SL 0.19-0.20 mm, SI 53-55); New Mexico . . . . . Solenopsis whitfordi

12
return to couplet #10
 * Head thicker (0.24 mm from dorsal to ventral surface), elongate but robust, sparsely punctate, 0.42 mm in length (CI 73-74); total length 1.2-1.3 mm; Chile . . . . . Solenopsis dysderces Snelling


 * Head thinner (0.18 mm from dorsal to ventral surface) elongate and slender, heavily punctate with punctures close to each other, head 0.36 mm in length (CI 67-77); total length 0.9-1.2 mm; Argentina (Santa Fe) . . . . . Solenopsis leptanilloides