Key to Iridomyrmex of the southwestern Australian Botanical Province

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This key to workers is based on: Heterick, B. E. 2009a. A guide to the ants of South-western Australia. Records of the Western Australian Museum, Supplement 76: 1-206. Part 1 PDF

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1

  • Propodeum large, conical (Iridomyrmex conifer species-group) (Figure 147) . . . . . 2
Figure 147.
  • Propodeum smaller, not conical (Figure 148) . . . . . 4
Figure 148.

2

return to couplet #1

  • Erect or suberect setae on pronotum usually lacking, but where present never more than 6 . . . . . Iridomyrmex conifer
Iridomyrmex conifer ST head CAS0172061-Antwiki.jpg
Iridomyrmex conifer ST side CAS0172061-Antwiki.jpg
  • More than 8 erect or suberect setae present on pronotum . . . . . 3

3

return to couplet #2

  • In full-face view, lateral margin of head generally lacking erect setae, but where present posterior setae larger than greatest diameter of scape, and distinctly curved . . . . . Iridomyrmex turbineus
Iridomyrmex turbineus HT ANIC32-000225 head 50-Antwiki.jpg
Iridomyrmex turbineus HT ANIC32-000225 side 32-Antwiki.jpg
  • In full-face view, lateral margin of head always with numerous short, erect setae, these setae always less than maximum scape diameter, and straight or slightly curved . . . . . Iridomyrmex setoconus
Iridomyrmex setoconus HT ANIC32-023696 head 50-Antwiki.jpg
Iridomyrmex setoconus HT ANIC32-023696 side 32-Antwiki.jpg

4

return to couplet #1

  • Large ants (HW > 1.5 mm); erect setae on all surfaces of tibiae and often of scapes; mesonotum with angle or arch between convex anterior sector and flat posterior sector (Figure 149); purple, green or blue iridescence present in SW species (“meat ants” in Iridomyrmex purpureus species-group) . . . . . 5
Figure 149.
  • Differing in one or more of the above characters (e.g. Figure 150) . . . . . 8
Figure 150.

5

return to couplet #4

  • Lateral and/or dorsal regions of head with weak green iridescence (and often purple iridescence) . . . . . Iridomyrmex viridiaeneus
Iridomyrmex viridiaeneus ST ANIC32-009177 head 32-Antwiki.jpg
Iridomyrmex viridiaeneus ST ANIC32-009177 side 20-Antwiki.jpg
  • Lateral and/or dorsal regions of head with purple or blue, but never green iridescence . . . . . 6

6

return to couplet #5

  • In profile, posterior region of pronotum (immediately anterior of the promesonotal suture) rising above the mesonotum in a short, strongly convex arch (Figure 151); sides of head with only very weak purplish iridescence or with no iridescence . . . . . Iridomyrmex reburrus
Figure 151.
Iridomyrmex reburrus HT w1head CAS0172049-Antwiki.jpg
Iridomyrmex reburrus HT w1side CAS0172049-Antwiki.jpg
  • In profile, posterior region of pronotum (immediately anterior of the promesonotal suture) rising above the mesonotum in a broad, uniform, weakly convex arch (Figure 152); sides of head usually with well-developed iridescence (commonly purple or blue) . . . . . 7
Figure 152.

7

return to couplet #6

  • Head and mesosoma dark reddish-brown to black; head often with strong blue iridescence . . . . . Iridomyrmex lividus
Iridomyrmex lividus w2head CAS0172041-Antwiki.jpg
Iridomyrmex lividus w2side CAS0172041-Antwiki.jpg
Iridomyrmex purpureus ANIC32-008690 head 32-Antwiki.jpg
Iridomyrmex purpureus ANIC32-008690 side 20-Antwiki.jpg

8

return to couplet #4

  • Frontal carinae of head capsule curved throughout their length (Iridomyrmex calvus species-group) (Figure 153) . . . . . 9
Figure 153.
  • Frontal carinae of head capsule sinuate or approximately straight medially (Figure 154) . . . . . 13
Figure 154.

9

return to couplet #8

  • Propodeum flattened, with propodeal spiracles situated dorsally near propodeal angles; petiolar node very low and broad; body black, with blue iridescence (Figure 155) . . . . . Iridomyrmex calvus group sp. JDM 1069
Figure 155.
  • Propodeum more rounded, propodeal spiracle situated laterally; petiolar node more developed, narrow (e.g. Figure 156) . . . . . 10
Figure 156.

10

return to couplet #9

11

return to couplet #10

  • Mesosoma with numerous short to medium-length (longest setae ≈ width of eye) erect setae . . . . . Iridomyrmex hesperus
Iridomyrmex hesperus HT head CAS0172052-Antwiki.jpg
Iridomyrmex hesperus HT side CAS0172052-Antwiki.jpg
  • Mesosoma often lacking erect setae, if present then confined to one or two pairs on pronotum and/or mesonotum, short (width of eye <) . . . . . Iridomyrmex calvus
Iridomyrmex albitarsus ANIC32-000083 head 63-Antwiki.jpg
Iridomyrmex albitarsus ANIC32-000083 side 32-Antwiki.jpg

12

return to couplet #10

  • Erect setae absent from antennal scape; head and mesosoma finely sculptured, the sculpture obscured by appressed pubescence . . . . . Iridomyrmex prismatis
Iridomyrmex prismatis HT head CAS0172064-Antwiki.jpg
Iridomyrmex prismatis HT side CAS0172064-Antwiki.jpg
  • Erect setae present on antennal scape; head and mesosoma shining and generally smooth, with only superficial microreticulation evident in some lights, the cuticle not obscured by appressed pubescence . . . . . Iridomyrmex innocens
Iridomyrmex innocens ANIC32-030662 head 50-Antwiki.jpg
Iridomyrmex innocens ANIC32-030662 side 40-Antwiki.jpg

13

return to couplet #8

  • Viewed from front, head capsule very long, up to twice as long as wide, its widest point well above its midpoint (Figure 157); vertex of head capsule often weakly to strongly convex; appendages long, femur and tibia about length of mesosoma (I. agilis species-group) . . . . . 14
Figure 157.
  • Viewed from front, head capsule ≤1.5 times as long as wide, its widest point at about its midpoint (Figure 158); vertex of head capsule straight or concave; appendages shorter, < length of mesosoma . . . . . 16
Figure 158.

14

return to couplet #13

Iridomyrmex agilis pale ANIC32-043285 head 25-Antwiki.jpg
Iridomyrmex agilis pale ANIC32-043285 side 20-Antwiki.jpg
  • Smaller species (HW < 1 mm); concolorous black or dark brown . . . . . 15

15

return to couplet #14

  • Pronotum weakly tapered anteriad, attached to head capsule well below level of vertex (Figure 159) . . . . . Iridomyrmex bicknelli
Figure 159.
Iridomyrmex bicknelli ANIC32-023685 head 40-Antwiki.jpg
Iridomyrmex bicknelli ANIC32-023685 side 32-Antwiki.jpg
  • Pronotum strongly tapered anteriad, attached to head capsule close to level of vertex (Figure 160) . . . . . Iridomyrmex agilis group sp. JDM 85
Figure 160.

16

return to couplet #13

  • Eye very large (eye length ≈ 1/3 of HL), strongly asymmetrical, with outer eye margin almost straight, inner margin convex (posterior lobe of eye also distinctly more narrowly convex than anterior lobe in many larger specimens); colour variable, ranging from depigmented yellow through light brown (most commonly) to black (I. hartmeyeri species-group) (Figure 161) . . . . . 17
Figure 161.
  • Eye smaller (eye length < 1/3 of HL), or eyes ovate or weakly asymmetrical; colour rarely pale (often brown or reddish hues, alone or in combination) (Figure 162) . . . . . 19
Figure 162.

17

return to couplet #16

Iridomyrmex hartmeyeri ANIC32-036832 head 40-Antwiki.jpg
Iridomyrmex hartmeyeri ANIC32-036832 side 32-Antwiki.jpg
  • Dorsum of mesosoma with erect and suberect setae . . . . . 18

18

return to couplet #17

  • Viewed from front, sides of head capsule with a few to many short, erect setae; antennal scape often with short, erect setae along its length (Figure 163) . . . . . Iridomyrmex hartmeyeri group sp. JDM 849
Figure 163.
  • Viewed from front, sides of head capsule without short, erect setae; antennal scape without erect setae except at extreme tip . . . . . Iridomyrmex dromus (Figure 164) / Iridomyrmex exsanguis (Figure 165)
Figure 164.
Iridomyrmex dromus ANIC32-043311 side 40-Antwiki.jpg
Figure 165.
Iridomyrmex exsanguis ANIC32-038611 side 50-Antwiki.jpg

19

return to couplet #16

  • Antennal scape with erect setae along its length . . . . . 20
  • Antennal scape with erect setae confined to the extreme tip . . . . . 23

20

return to couplet #19

  • In full-face view, head shape (excluding the mandibles) variably trapezoidal, the posterior (occipital) angles moderately to much wider apart than the anterior angles (i.e. where mandibles are articulated); size generally larger, HW ≥ 1.5 mm (Figure 166) . . . . . Iridomyrmex discors
Figure 166.
Iridomyrmex discors ST side CAS0172053-Antwiki.jpg
  • In full-face view, head shape (excluding the mandibles) rectangular, sides of head capsule convex to almost straight, posterior angles approximately as wide apart as anterior angles (Figure 167); size generally smaller, HW ≤ 1.5 mm . . . . . 21
Figure 167.

21

return to couplet #20

  • In profile, mesosoma strongly biconvex, the pronotum rounded and strongly declivitous towards head; propodeum truncate and raised above plane of mesonotum, its dorsal face about as long as its declivitous face (Figure 168) . . . . . Iridomyrmex chasei (in part - also #27)
Figure 168.
Iridomyrmex chasei ANIC32-039051 head 40-Antwiki.jpg
Iridomyrmex chasei ANIC32-039051 side 32-Antwiki.jpg
  • In profile, mesosoma undulant, with pronotum gently convex; propodeum rather long, and on same plane as mesonotum; its dorsal face distinctly longer than its declivitous face (Figure 169) . . . . . 22
Figure 169.

22

return to couplet #21

  • Erect setae sparse, mostly confined to outer surface of scape (Figure 170) Iridomyrmex sp. JDM 846
Figure 170.
  • Erect setae abundant, and found on all surfaces of scape for most of its length (Figure 171) . . . . . Iridomyrmex gracilis spurcus
Figure 171.

23

return to couplet #19

  • Propodeum longer than high, without a not iceable propodeal angle (generally rather large, gracile ants (Figure 172). (n.b. Iridomyrmex anceps (Roger) will also key out here, but is smaller than the two species in couplet 23, i.e. HW 0.8 mm < compared with HW 0.9 mm >) . . . . . 24
Figure 172.
  • Propodeum about as long as high with a not iceably protuberant, though blunt propodeal angle (non-gracile ants) (I. rufoniger species-group) (e.g. Figure 173) . . . . . 25
Figure 173.

24

return to couplet #23

  • Head and mesosoma brick-red or reddish orange . . . . . Iridomyrmex sp. JDM 133
Iridomyrmex brunneus ANIC32-038197 head 40-Antwiki.jpg
Iridomyrmex brunneus ANIC32-038197 side 25-Antwiki.jpg

25

return to couplet #23

  • In full-face view, vertex of head weakly to strongly concave; in profile, pronotum strongly rounded, arising abruptly anteriad; > 8 erect setae on its dorsum; propodeum rising above level of metanotum, its dorsum either protuberant or flattened, if the latter then often with a minute indentation . . . . . 26
  • Without the full suite of the above characters (though one or more of these features may be present) (several species in the mattiroloi complex) . . . . . 28

26

return to couplet #25

  • Large, broad-headed species (HW ≥ 0.8 mm, often > 1 mm); gaster with distinct greenish or greenish-blue iridescence . . . . . Iridomyrmex rufoniger
Iridomyrmex rufoniger ANIC32-023677 head 50-Antwiki.jpg
Iridomyrmex rufoniger ANIC32-023677 side 40-Antwiki.jpg
  • Smaller species (HW ≤ 0.5 mm); gaster with, at most, weak, coppery iridescence (ants in the I. chasei complex) . . . . . 27

27

return to couplet #26

  • Brown species, usually concolorous (mesopleuron may have lighter areas); erect setae on pronotum 12 <; propodeum flattened, often slightly indented medially (Figure 174) . . . . . I. chasei concolor (=Iridomyrmex chasei) (in part - also #21)
Figure 174.
Iridomyrmex chasei ANIC32-039051 head 40-Antwiki.jpg
Iridomyrmex chasei ANIC32-039051 side 32-Antwiki.jpg
  • Orange-and-brown species, darker specimens always with some orange areas on mesosoma; erect setae on mesosoma 15 ≥; propodeum usually rounded, occasionally indented medially (Figure 175) . . . . . I. chasei yalgooensis (=Iridomyrmex chasei) (in part - also #21)
Figure 175.

28

return to couplet #25

  • Worker with at least a few minute erect setae on mesosoma . . . . . 30

29

return to couplet #28

  • Eye larger (length 0.25 > × length head capsule); shades of medium to dark brown; drier north and north-east of SWBP . . . . . Iridomyrmex suchieri
Iridomyrmex suchieri ANIC32-036828 head 40-Antwiki.jpg
Iridomyrmex suchieri ANIC32-036828 side 32-Antwiki.jpg
  • Eye smaller (length 0.25 < × length head capsule); dark brown to black with bluish-green iridescence; south coast. . . . . Iridomyrmex mattiroloi complex sp. JDM 845

30

return to couplet #28

  • In full-face view, sides of head capsule with 6 > erect setae (Figure 176) . . . . . Iridomyrmex suchieri (population 2)
Figure 176.
Iridomyrmex suchieri ANIC32-036828 head 40-Antwiki.jpg
Iridomyrmex suchieri ANIC32-036828 side 32-Antwiki.jpg
  • In full-face view, sides of head capsule with 3 ≤ erect setae, setae usually lacking (Figure 177) . . . . . 31
Figure 177.

31

return to couplet #30

  • In profile, anterior pronotum rising more-or-less steeply towards its junction with mesonotum (Figure 178a); in dorsal view, sides of pronotum forming a symmetrical curve (Figure 178b); ant black or greyish-brown (brownish in northern sandplains) with blue to greenish-yellow iridescence; propodeum smoothly rounded (Figure 179); eye smaller (length 0.25 < × length head capsule) . . . . . Iridomyrmex splendens
Figure 178a.
Figure 178b.
Figure 179.
Iridomyrmex splendens ANIC32-023684 head 50-Antwiki.jpg
Iridomyrmex splendens ANIC32-023684 side 40-Antwiki.jpg
  • In profile, anterior pronotum forming a gradual, even curve towards its junction with mesonotum (Figure 180); in dorsal view, sides of pronotum forming an asymmetrical curve (Figure 181); ant usually a coppery brown, rarely with patches of blue to greenish-yellow iridescence on body; propodeum often not smoothly rounded in profile, its dorsum slightly to moderately flattened posteriad (Figure 182a) or protuberant (Figure 183a); eye larger (length 0.25 > × length head capsule) . . . . . 32
Figure 180.
Figure 181.
Figure 182a.
Figure 183a.

32

return to couplet #31

  • Dorsum of propodeum sloping, slightly flattened posteriad, propodeal angle indistinct (Figure 182a); scape longer, exceeding vertex of head capsule by more than 0.25 × its length (Figure 182b) . . . . . Iridomyrmex continentis
Figure 182a.
Figure 182b.
Iridomyrmex continentis ANIC32-013632 head 63-Antwiki.jpg
Iridomyrmex continentis ANIC32-013632 side 40-Antwiki.jpg


  • Dorsum of propodeum flat or weakly convex, nearly always connecting with the declivitous face through a distinct, though blunt, angle (Figure 183a); scape shorter, exceeding vertex of head capsule by much less than 0.25 × its length (Figure 183b) . . . . . Iridomyrmex suchieri
Figure 183a.
Figure 183b.
Iridomyrmex suchieri ANIC32-036828 head 40-Antwiki.jpg
Iridomyrmex suchieri ANIC32-036828 side 32-Antwiki.jpg