Key to Malagasy Nesomyrmex sikorai group workers

This worker key to the exclusively Malagasy N. angulatus group is based on: Csosz, S. & Fisher, B.L. 2016. Taxonomic revision of the Malagasy members of the Nesomyrmex angulatus species group using the automated morphological species delineation protocol NC-PART-clustering. PeerJ 4:e1796 doi:10.7717/peerj.1796

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 * Nesomyrmex
 * Key to Nesomyrmex species groups of the Malagasy region
 * Diagnosis of Nesomyrmex species groups of the Afrotropical and Malagasy regions

1

 * Scapes very short: SL/CS < 0.73 [0.679, 0.720], petiolar node very short: NOL/CS < 0.3 [0.254, 0.279] . . . . . Nesomyrmex reticulatus


 * Scapes longer: SL/CS > 0.73 [0.74, 0.872], petiolar node longer: NOH/CS 0.3 > [0.312, 0.358] . . . . . 2

2
return to couplet #1
 * Propodeal spines curving downward, blunt, and very long: SPST/CS > 0.36 [0.364, 0.459] . . . . . 3


 * Propodeal spines triangular, acute, and shorter: SPST/CS < 0.36 [0.219, 0.352] . . . . . 4

3
return to couplet #2
 * Vertex rugose, ground sculpture areolate, dull. In full-face view, compound eyes positioned forward and closer to the anterior clypeal border: PoOC/CL > 0.455 [0.464, 0.498] . . . . . Nesomyrmex retusispinosus


 * Vertex smooth, main sculpture absent, ground sculpture inconspicuously areolate, shiny. In full-face view, compound eyes positioned in the middle of the longitudinal axis of head or closer to the posterior occipital border: PoOC/CL < 0.455 [0.411, 0.449] . . . . . Nesomyrmex tamatavensis

4
return to couplet #2
 * Black species. Eyes protuberant in full-face view: CW/ML: > 0.73 [0.727, 0.810], [5–95% percentiles: 0.732, 0.791] . . . . . 5


 * Workers yellow to light brown. Eyes non-protuberant in full-face view: CW/ML: <0.73 [0.647, 0.738], [5–95% percentiles: 0.670, 0.727] . . . . . . 7

5
return to couplet #4
 * Main sculpture on vertex and on the dorsum of mesosoma inconspicuously areolate or absent partly, ground sculpture smooth and shiny. Eyes moderately protuberant in full-face view: CL/CW > 1.09 [1.097, 1.149] . . . . . Nesomyrmex modestus


 * Main sculpture on vertex and on the dorsum of mesosoma present and coarse areolate or costate, ground sculpture inconspicuously areolate or absent. Eyes strongly protuberant in full-face view: CL/CW < 1.09 [0.998, 1.079] . . . . . 6

6
return to couplet #5
 * Main sculpture on vertex coarse areolate, ground sculpture inconspicuously areolate. Dorsum of petiolar node rugoso-reticulate, dull. The best morphometric ratio PSTI/SPTI ≤ 2.5 [1.966, 2.50] . . . . . Nesomyrmex sikorai


 * Main sculpture on vertex longitudinal costate, ground sculpture inconspicuously areolate. Dorsum of petiolar node smooth and shiny. The best morphometric ratio PSTI/SPTI > 2.5 [2.512, 3.40] . . . . . Nesomyrmex striatus

7
return to couplet #4
 * Postpetiole longer, anterolateral angles of mesosoma less distant: PSTI/PPW > 1.84 [1.579, 1.878], [5–95% percentiles: 1.636, 1.826]. Occurs on higher ground > 500 m . . . . . Nesomyrmex excelsior


 * Postpetiole shorter, anterolateral angles of mesosoma widely distant: PSTI/PPW 1.84 [1.791, 2.117], [5–95% percentiles: 1.794, 2.095]. Occurs on lower elevations < 500 m . . . . . Nesomyrmex rugosus