Key to Iridomyrmex of the southwestern Australian Botanical Province

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.

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• Australia
• SWBP
• Iridomyrmex

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

• 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

• 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

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

• 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.

• 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

• Head and mesosoma reddish-brown; head with purple iridescence . . . . . Iridomyrmex purpureus

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

• Tibiae devoid of erect setae . . . . . 11

• Tibiae with regularly placed erect setae . . . . . 12

11

return to couplet #10

• Mesosoma with numerous short to medium-length (longest setae ≈ width of eye) erect setae . . . . . Iridomyrmex hesperus

• 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

12

return to couplet #10

• Erect setae absent from antennal scape; head and mesosoma finely sculptured, the sculpture obscured by appressed pubescence . . . . . Iridomyrmex prismatis

• 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

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

• Larger species (HW > 1 mm); red-and-black . . . . . Iridomyrmex agilis

• 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.

• 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

• Dorsum of mesosoma without erect and suberect setae . . . . . Iridomyrmex hartmeyeri

• 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

Figure 165.

Iridomyrmex exsanguis

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

• 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.

• 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

• Head brown, mesosoma orange-brown . . . . . Iridomyrmex brunneus

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

• 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.

• 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 without erect setae on mesosoma . . . . . 29

• 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

• 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.

• 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.

• 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.

• 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.