Key to Nearctic Nylanderia Workers

This worker key is based on: Kallal, R.J. & LaPolla, J.S. 2012. Monograph of Nylanderia (Hymenoptera: Formicidae) of the World, Part II: Nylanderia in the Nearctic. Zootaxa 3508, 1-64.

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1

 * Mesonotum with pubescence . . . . . 2


 * Mesonotum without pubescence . . . . . 6

2
return to couplet #1
 * Mesopleuron entirely covered with pubescence . . . . . 3


 * Mesopleuron not entirely covered with pubescence . . . . . 4

3
return to couplet #2
 * Overall color reddish-brown; typically REL less than 30; mesosoma macrosetae long (index of longest pronotal macrosetae/ propodeum height at least 60) . . . . . Nylanderia fulva or Nylanderia pubens *


 * Overall color dark brown to almost black; typically REL more than 30; mesosoma macrosetae short (index of longest pronotal macrosetae/propodeum height less than 60) . . . . . Nylanderia bourbonica

4
return to couplet #2
 * Overall body yellow in color . . . . . Nylanderia guatemalensis


 * Overall body brown in color . . . . . 5

5

 * Gastral macrosetae densely distributed; HW ≥ 0.59 mm; gastral pubescence densest along segmental margins . . . . . Nylanderia bruesii


 * Gastral macrosetae sparsely distributed; HW < 0.59 mm; gastral pubescence equally distributed . . . . . Nylanderia steinheili

6
return to couplet #1
 * Whitish to pale yellow in color; macrosetae white . . . . . Nylanderia phantasma


 * Darker in color than above; if yellow, then macrosetae are brown to black . . . . . 7

7
return to couplet #6
 * Head ovate with distinct medial emargination along posterior margin, and SMC at least 10, and body overall densely setose, with black macrosetae contrasting strongly with yellow cuticle . . . . . Nylanderia hystrix


 * Not matching the combination of characters listed above . . . . . 8

8
return to couplet #7
 * Cuticle usually with bluish reflections under microscopic examination; pronotum with distinct concavity, giving it an angular appearance in lateral view . . . . . Nylanderia austroccidua


 * Cuticle rarely with bluish reflections under microscopic examination; pronotum not angular in appearance in lateral view . . . . . 9

9
return to couplet #8
 * Antennae, mesosoma and legs yellowish, and SMC 5 or more, and 3 ocelli apparent; 1st gastral tergite often yellowish and contrasting with remainder of gaster . . . . . Nylanderia flavipes


 * Overall coloration variable; SMC variable; ocelli may or may not be apparent; 1st gastral tergite always same color as remainder of gaster . . . . . 10

10
return to couplet #9
 * Brown in color, with mesocoxae and metacoxae whitish, contrasting strongly with mesosoma; cephalic pubescence moderate to dense . . . . . 11


 * Yellow to brown in color, typically with mesocoxae and metacoxae the same color as mesosoma; if mesocoxae and metacoxae whitish and contrasting strongly with mesosoma then cephalic pubescence sparse to absent . . . . . 12

11
return to couplet #10
 * Scape macrosetae count 5 or more; head length typically > 0.59 mm (HL: 0.59–0.74); usually uniform brown or with darker gaster . . . . . Nylanderia faisonensis


 * Scape macrosetae count less than 5; head length typically < 0.59 mm (HL: 0.47–0.59); usually bicolored with darker head and gaster . . . . . Nylanderia wojciki

12
return to couplet #10
 * Scape macrosetae absent . . . . . 13


 * Scape macrosetae present . . . . . 14

13
return to couplet #12
 * Overall brown in color, with yellowish scapes contrasting with head color . . . . . Nylanderia parvula


 * Overall yellow in color, with yellowish scapes not contrasting with head color . . . . . Nylanderia trageri

14
return to couplet #12
 * Overall moderate to dark brown, with mesocoxae and metacoxae not strongly contrasting with mesosoma; moderate to dense cephalic pubescence; with a dense, neat band of pubescence along the dorsal margin of propodeum . . . . . Nylanderia concinna


 * If brown in color, cephalic pubescence sparse to absent; if yellow in color, cephalic pubescence moderate to dense, but pubescence absent on propodeum . . . . . 15

15
return to couplet #14
 * Cephalic pubescence moderate to dense . . . . . 16


 * Cephalic pubescence sparse to absent . . . . . 17

16
return to couplet #15
 * Gaster becomes brownish distally; gaster macrosetae densely distributed . . . . . Nylanderia arenivaga


 * Gaster uniform yellow in color; gaster macrosetae not densely distributed . . . . . Nylanderia querna

17
return to couplet #15
 * HL at least 0.67 mm; SL at least 0.76 mm; scapes usually with decumbent pubescence; posterior margin of head usu-ally without medial emargination . . . . . Nylanderia magnella


 * HL at most 0.67 mm; SL less than 0.76 mm; scapes usually without decumbent pubescence; posterior margin of head usually with slight medial emargination . . . . . 18

18**
return to couplet #17
 * Head with subparallel lateral margins in full face view, appearing relatively squarish; typically REL > 24 . . . . . Nylanderia vividula
 * Head with convex lateral margins in full face view, appearing relatively ovate; typically REL< 24 . . . . . Nylanderia terricola

* Workers of the introduced species fulva and pubens cannot be separated based on morphology. For morphological identification males are necessary. For further details see Gotzek et al., 2012.

** Workers of vividula and terricola cannot be reliably identified to species based on morphology. It appears that western U.S. terricola specimens are lighter than vividula, but this distinction is not maintained elsewhere in their range. However, males of the two species can be easily distinguished.