Key to Melophorus of the southwestern Australian Botanical Province

This key to minor workers is based on: [[Media:Heterick 2009.pdf|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]]

Although this genus is polymorphic, there is generally relatively less difference, apart from the broad head capsule in the major, between the major and other worker castes than there is in genera like Pheidole and Camponotus. The characteristics of all worker castes of Melophorus, therefore, are included in this key. The major workers for some species, however, are unknown.

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 * Australia
 * Melophorus

1

 * Propodeum in major and minor workers armed with stout denticles, directed vertically; head, mesosoma and nodes strongly shagreenate; matt in appearance; minor worker with elongate head capsule, in full-face view, about three times as long as wide (very rare, sandplain E of Albany and Eneabba region) (Figure 332) . . . . . Melophorus majeri


 * Propodeum unarmed in all worker castes; appearance otherwise not as above . . . . . 2

2
return to couplet #1
 * In profile, head (at least of minor and media workers) extremely flattened (Figure 333); outline of dorsum of mesosoma almost straight (characteristics of major worker unknown) . . . . . Melophorus sp. JDM 787


 * In profile, head not extremely flattened; outline of dorsum of mesosoma usually sinuate, with pronotum and/or propodeum elevated above plane of mesonotum . . . . . 3

3
return to couplet #2
 * In profile, propodeum elongate, often descending obliquely towards its junction with petiole (mainly M. iridescens species-group) (e.g. Figure 334) . . . . . 4


 * In profile, propodeum compact, smoothly rounded or truncate with distinct dorsal and declivitous faces (e.g. Figure 335) . . . . . 6

4
return to couplet #3
 * In profile, pronotum very weakly convex; propodeum weakly convex with long dorsal face (gracile, uniformly orange ants; arid to semi-arid environments) . . . . . Melophorus sp. JDM 199


 * In profile, pronotum distinctly rounded; propodeum describing oblique arc (Figure 334) . . . . . 5

5
return to couplet #4
 * Larger (major workers TL ≈ 7–9 mm, media and minor workers TL ≈ 4–6 mm); metanotal groove in all workers usually more deeply impressed, so metathoracic spiracles are more-or-less dorsally situated (Figure 335); minor workers most commonly with red or reddish-brown foreparts (drier areas of SWBP) . . . . . Melophorus sp. near aeneovirens (JDM 545)


 * Smaller (major workers TL ≈ 5–6 mm, media and minor workers TL ≈ 3–4 mm); metanotal groove in all workers usually more shallowly impressed, so metathoracic spiracles are more-or-less laterally situated (Figure 337); minor workers most commonly with ochre to dark brown foreparts and brown to black gasters, never red, and usually not reddish-brown (widespread, but most abundant in wetter, forested areas of the south-west) . . . . . Melophorus insularis

6
return to couplet #3
 * Minor worker with many short, peg-like bristles covering the body (Figure 338); cuticle finely microreticulate with a yellowish sheen (major worker unknown) . . . . . . Melophorus sp. JDM 613


 * Minor worker without peg-like bristles; appearance of cuticle not as above . . . . . 7

7
return to couplet #6
 * Mandible very large (2/3–3/4 length of head capsule), hatchet-shaped (Figure 339) . . . . . Melophorus potteri gp. sp. JDM 1032


 * Mandible of normal proportions, triangular or strap-like in shape (e.g. Figures 340, 341) . . . . . 8

8
return to couplet #7
 * Propodeal spiracle very large and conspicuous, about 2/3 x length of declivitous face of propodeum; spiracle placed slightly nearer declivitous face of propodeum than metanotal groove (Figure 342) . . . . . 9


 * Propodeal spiracle smaller and/or placed much closer to declivitous face of propodeum (often on edge of its surface) (Figures 343, 344) . . . . . 10

9
return to couplet #8
 * In profile, anterior margin of clypeus protruding (Figure 345); in full-face view, frons unsculptured, smooth and glossy . . . . . Melophorus potteri


 * In profile, anterior margin of clypeus curved inwards (Figure 346); in full-face view, sculpture of frons finely microreticulate, matt or with a dull sheen . . . . . Melophorus potteri gp. sp. JDM 1082

10
return to couplet #8
 * Posterior of mesonotum extended as a lobe, overhanging the propodeum; dorsal face of propodeum very narrow, almost wedge-shaped in profile; metathoracic spiracle facing laterad, in one species situated well before junction of mesonotum and propodeum (Figure 347) . . . . . 11


 * Mesonotum less developed, not overhanging propodeum; dorsal face of propodeum longer; metathoracic spiracle usually facing dorsad (e.g. Figure 348) . . . . . 12

11
return to couplet #10
 * Major and minor workers with scattered, short, erect setae on mesosoma; appressed setae longer (length ≈ greatest width of antennal scape) almost adjoining on mesosoma and gaster; metathoracic spiracle situated near junction of mesonotum and propodeum . . . . . Melophorus sp. JDM 230


 * Minor worker lacking erect setae on mesosoma; appressed setae shorter (length < greatest width of antennal scape) well separated on mesosoma and gaster; metathoracic spiracle situated well before junction of mesonotum and propodeum . . . . . Melophorus sp. JDM 1063

12
return to couplet #10
 * Dorsal surfaces of body with short, modified, spatulate setae (Figure 349); body covered with fine, whitish-yellow pubescence (more distinct in minor workers) . . . . . Melophorus sp. JDM 784


 * Either modified setae absent, or, if present, then confined to pronotum and body not pubescent as above . . . . . 13

13
return to couplet #12
 * Body, legs and antenna of minor covered in long, erect and downy, appressed setae; body slender, gracile (Iridomyrmex-like); in profile eye very large (eye length >1/3 length of head capsule) (Figure 350); cuticle matt, finely microreticulate; clypeus protruding (major worker unknown) . . . . . Melophorus sp. JDM 788


 * Body often smooth and shining with few erect setae; if hairy, then either body not gracile and Iridomyrmex–like, or eye smaller or clypeus not protruding . . . . . 14

14
return to couplet #13
 * Major and minor worker with fine pubescence, silvery in minor worker, mesosoma with many short, erect setae; in profile pronotum and mesonotum of minor worker gently convex to almost straight . . . . . Melophorus mjobergi


 * If major worker also with fine pubescence (usually lacking), then pronotum and mesonotum of minor worker more convex, often protuberant . . . . . 15

15
return to couplet #14
 * Major and minor workers with abundant fine pubescence on frons of head capsule (relatively large, reddish northern species) . . . . . Melophorus sp. JDM 1105


 * Major and minor workers without abundant fine pubescence on frons of head capsule . . . . . 16

16
return to couplet #15
 * Mesonotum bulbous, translucent or even transparent, ground colour distinctly paler than surrounding mesosoma (small species, TL of minors ≈ 2 mm) . . . . . Melophorus sp. JDM 500


 * Mesonotum, if protuberant, not translucent, usually the same colour as rest of mesosoma but may be slightly paler . . . . . 17

17
return to couplet #16
 * Large size discrepancy between smallest minors (HW ≤ 0.5 mm) and largest major workers (HW ≥ 2mm); pale orange to depigmented yellow ants, with colour of frons often gradually darkening towards vertex; declivitous face of propodeum strongly oblique when seen in profile (e.g. as in Figure 343); minor workers without erect setae on dorsum of mesosoma . . . . . Melophorus ludius sulla


 * Size more uniform among subcastes (see couplet 18 below); if very pale, then without above combination of features (propodeum of small yellow or yellowish workers often with weakly oblique or abruptly vertical declivitous face (e.g. as in Figure 353 below) . . . . . 18

18
return to couplet #17
 * Small species (major worker HW ≤ 1 mm, minor worker HW ≤ 0.5 mm) . . . . . 19


 * Species larger (major worker HW ≥ 2mm, minor worker HW ≥ 0.8 mm) . . . . . 26

19
return to couplet #18
 * Major and minor workers with erect, usually long setae on mesosoma . . . . . 20


 * Minor workers, at least, glabrous or pubescent, without longer, erect setae on mesosoma . . . . . 24

20
return to couplet #19
 * In minor worker (major worker unknown) sculpture of head and mesosoma completely microreticulate, appearance of cuticle uniformly matt, dull; pilosity consisting of two or three very short, bristle-like setae, arranged transversely across central sector of pronotum . . . . . Melophorus sp. JDM 1180


 * Sculpture of minor worker not as above, sculpture reduced or absent on pronotum and mesonotum particularly, these parts more-or-less shining in appearance; pilosity more extensive, usually consisting of long, fine erect, curved setae . . . . . 21

21
return to couplet #20
 * In minor worker, pronotum globose (Figure 351); propodeum truncate or sharply rounded in profile; erect setae on pronotum and mesonotum relatively long (> diameter of eye); eye moderate (eye length 1/5 x length of head capsule); viewed dorsally, pronotum and mesonotum smooth and shiny in appearance in minor worker (Major worker similar in appearance to Melophorus sp. JDM 176 – see couplet 22 – but with scattered erect setae on entire mesosoma) . . . . . Melophorus sp. JDM 470


 * In minor worker, pronotum either not noticeably globose (Figure 352); or erect setae on pronotum and mesonotum relatively short (≤ diameter of eye) (single worker of Melophorus sp. JDM 176); eye larger (eye length ≈ 1/3 length of head capsule) in remaining spp . . . . . 22

22
return to couplet #21
 * Eye moderate, eye length 1/5 x length of head capsule; in profile, propodeum of minor worker truncate (Figure 353), its dorsal face < half length of its declivitous face; erect setae on mesosoma short bristles, their length ≈ greatest width of antennal scapes . . . . . Melophorus sp. JDM 176 (in part - also ) (a single minor worker)


 * Eye large, eye length ≈ 1/3 length of head capsule; in profile, propodeum of minor worker usually distinctly rounded, though may be narrowly so (Figure 354); erect setae on mesosoma fine, not bristle-like, length usually > greatest width of antennal scapes . . . . . 23

23
return to couplet #22
 * Inner edge of antennal scape in major and minor worker with many erect setae arising at angle of 90° (Figure 355); mesosoma clothed in fine, curved erect setae . . . . . Melophorus sp. JDM 1070


 * Antennal scape lacking erect setae (Figure 356); mesosoma with moderate to sparse erect pilosity . . . . . Melophorus sp. JDM 786

24
return to couplet #19
 * In full-face view, head of minor worker narrow, longer than wide with a strongly convex vertex (Figure 357a); in profile, propodeum rising above level of mesonotum, which is straight; hind femur gradually decreasing in diameter to about its midpoint, thereafter femur of same diameter up to its articulation with the tibia (Figure 357b) (possible major worker known but not confirmed) . . . . . Melophorus JDM 1102


 * In full-face view, head of minor worker more-or-less square, about as long as wide; vertex straight or weakly convex (Figure 358); in profile, propodeum below level of mesonotum which is gently to strongly convex; hind femur gradually decreasing in diameter virtually throughout its entire length (Figure 359)

25
return to couplet #24
 * Major worker with scattered, longer (i.e. eye width >), thin, erect setae on dorsum of pronotum, mesonotum and propodeum; cuticle of minor worker almost completely smooth and shining; mostly light, depigmented yellow with greyish or black gaster, head may be light orangered (n.b. widespread, dark minor workers, presently unassociated with majors, may belong to another species) . . . . . Melophorus ANIC sp. 3


 * Major worker with a few shorter (i.e. eye width <), stout, erect setae on dorsum of pronotum and sometimes mesonotum; cuticle of minor worker finely shagreenate or with superficial microreticulation, colour variable, often concolorous brown or reddish-brown or with foreparts orange, legs brown, gaster black . . . . . Melophorus sp. JDM 176 (most workers) (in part - also )

26
return to couplet #18
 * In profile, head capsule of major and media workers massive and broad, eye placed well in front of midline of head capsule (Figure 360a), length of head capsule and mandible in major and media workers approximately length of mesosoma; basal margin of mandible in media workers may have a tusk-like tooth (Figure 360b) (M. wheeleri complex) . . . . . 27


 * In profile, head capsule of major and media workers less massive and broad, eye placed slightly in front of midline of head capsule (Figure 361), length of head capsule in major and media workers less than length of mesosoma; basal margin of mandible in media workers without tusk-like tooth . . . . . 29

27
return to couplet #26
 * Mandible of minor worker with 7 or more denticles; frons of head capsule of major and minor worker dull and finely sculptured . . . . . Melophorus wheeleri


 * Mandible of minor worker with 5 or 6 denticles; frons of head capsule of major and minor worker with vestigial or no sculpture, shining in appearance . . . . . 28

28
return to couplet #27
 * Head orange to chocolate, mesosoma orange to dark reddish brown, gaster black; media worker with tooth in middle of basal margin of mandible (Figure 360b); masticatory margin of mandible in minor worker weakly oblique, basal tooth strongly offset (Figure 362) . . . . . Melophorus wheeleri complex sp. JDM 783


 * Mesosoma and gaster shining black, head slightly lighter; media worker without tooth in middle of basal margin of mandible (NE fringe of SWBP); masticatory margin of mandible in minor worker weakly offset (Figure 363) . . . . . Melophorus wheeleri complex sp. JDM 1077

29
return to couplet #26
 * In minor worker, mesosoma rarely with a few erect setae, these lacking in most specimens; sculpture of head and mesosoma reduced or absent, appearance shining . . . . . 30


 * In minor worker, mesosoma with many erect, usually long setae; head and mesosoma usually dull, shagreenate, less often shining . . . . . 31

30
return to couplet #29
 * In profile, mesonotum of major and minor worker moderately convex (Figure 364); major worker without setae or with 6 < erect setae, mainly on pronotum; propodeum tending to truncate in outline. . . . . Melophorus turneri perthensis


 * In profile, mesonotum of major and minor worker straight or nearly so (Figure 365); major worker with 6 > erect setae on pronotum; propodeum generally more rounded in outline . . . . . Melophorus turneri (in part - also )

31
return to couplet #29
 * Femora with whorls of long, erect, straight setae (Figure 366), head, mesosoma and gaster with very many long, fine, erect setae . . . . . Melophorus turneri complex sp. JDM 791


 * Femora lacking whorls of long, erect, straight setae, setae mainly appressed or decumbent (Figure 367); setae on head, mesosoma and gaster shorter, often giving a shaggy appearance to the ant . . . . . 32

32
return to couplet #31
 * In profile, anterior margin of minor worker clypeus projecting, so mandibles close well underneath it (Figure 368) (putative major worker cannot be distinguished from M. bruneus McAreavey majors) . . . . . Melophorus mjobergi complex sp. JDM 1121


 * In profile, anterior margin of minor worker clypeus curved inward, so mandibles just below it and on the same plane (Figure 369) . . . . . 33

33
return to couplet #32
 * Eye large and protuberant (eye length 1/3 head length <) (370a); hind tibia without erect and semi-erect setae (Figure 370b) (major worker unknown) . . . . . Melophorus bruneus complex sp. JDM 600


 * Either eye smaller, less protuberant (eye length ≈ . head capsule) (Figure 371), or hind tibia with semi-erect setae . . . . . 34

34
return to couplet #33
 * Antennal scape finely sculptured, with many erect setae on all surfaces (Figure 372); sculpture in minor and media workers shagreenate; setae on body rather short and erect (≤ greatest antennal width) . . . . . Melophorus bruneus complex sp. JDM 520


 * Antennal scape smooth, setae predominantly appressed, erect setae nearly always more sparse than in M. bruneus complex sp. JDM 520, normally present on outer surface only and may be completely absent (Figure 373); sculpture in minor and media workers reduced, so cuticle is usually shining; setae on body longer (except in coastal populations) (longest setae ≥ greater than greatest antennal width, and curved, giving ant a shaggy appearance) . . . . . Melophorus turneri (in part - also )