Key to Monomorium of the southwestern Australian Botanical Province

This worker key 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 2.]]

Monomorium kilianii has also been recorded from the south-west but the record of this eastern Australian species is very dubious. This ant is not included in this key.

This key includes the species Trichomyrmex destructor.

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 * Australia
 * SWBP
 * Monomorium

1

 * Compound eyes absent (may occasionally be represented by minute fleck of pigment) . . . . . Monomorium hildebrandti gp. sp. JDM 438


 * Compound eyes present, moderate to large in size . . . . . 2

2
return to couplet #1
 * Antenna 10-segmented . . . . . 3


 * Antenna 11 or 12-segmented . . . . . 4

3
return to couplet #2
 * PF 2,3; number of mandibular teeth 5; propodeum armed with sharp denticles . . . . . Monomorium decuria

(pt.)
 * PF 1,2; number of mandibular teeth 4; propodeum unarmed . . . . . Monomorium sydneyense

4
return to couplet #2
 * Antenna 11-segmented . . . . . 5


 * Antenna 12-segmented . . . . . 15

5
return to couplet #4
 * Viewed in profile, eye distinctly oblique, often reaching to venter of head capsule, distance from mandible usually much less than length of eye (Figure 600) . . . . . 6


 * Viewed in profile, eye situated along longitudinal axis of head capsule, distance from mandible at most only slightly less than length of eye (Figure 601) . . . . . 7

6
return to couplet #5
 * PF 2,2; head square (Figure 602) . . . . . Monomorium eremophilum


 * PF 1,2; head rectangular (Figure 603) . . . . . Monomorium nanum

7
return to couplet #5
 * Propodeum distinctly cuboidal, laterally carinate, or with lamellae on propodeal lobes extending to or near propodeum; propodeal and mesopleural sculpture often shagreenate-punctate (Figure 604) . . . . . 8


 * Propodeum more-or-less rounded, with small, inconspicuous propodeal lobes; propodeal and mesopleural sculpture never shagreenate-punctate, usually absent, if present, then confined to a few striae, particularly around the lower mesopleuron (Figure 605) . . . . . 14

8
return to couplet #7
 * Mandible with three distinct teeth; eye small (approximately ≈ width of antennal scape); propodeum smooth and shining with only vestigial striae; propodeum with declivitous face long and oblique, carinate at sides and sometimes with small lamellae at propodeal angle (Figure 606); anterior clypeal margin rounded; long erect and suberect setae absent from mesosoma . . . . . Monomorium arenarium


 * Mandible usually with four teeth and denticles (basal tooth may be minute or an offset angle); if clypeal margin rounded then eye larger; propodeum shagreenate or otherwise sculptured (e.g. Figure 607) . . . . . 9

9
return to couplet #8
 * Yellow species or yellowish with reddish-brown head and gaster; erect and suberect setae on head and mesosoma; propodeum cuboidal to slightly elongate; eye large (eye width ≥ 2 × greatest width of antennal scape) (Figure 607). . . . . . Monomorium silaceum


 * Never with above combination of characters; if yellow with a cuboidal propodeum and large eye, then erect and suberect setae absent from head and mesosoma . . . . . 10

10
return to couplet #9
 * Mesonotal and mesopleural sectors of promesonotum distinctly microreticulate; in dorsal view, faint, longitudinal striae also often evident on mesonotal sector; eyes usually large (eye diameter > greatest antennal width) (Fig, 608); ant shades of reddish-orange to brown, alone or in combination . . . . . 11


 * Mesonotal sector of promesonotum, at least, smooth and shining with microreticulate sculpture and faint, longitudinal striae always absent; if ant with strong microreticulation on mesopleural sector and on propodeum, then eyes usually moderate to small in non-yellow specimens (eye diameter ≤ greatest antennal width) (Figure 609: M. sydneyense Forel); colour various . . . . . 12

11
return to couplet #10
 * In profile, mesosoma an even arc, metanotal grove appearing as a slit between promesonotum (which is short) and propodeum; metanotal groove with few if any cross ribs; eye generally oval, smaller (eye width 1–1.5 × greatest width of antennal scape); erect setae generally absent on mesosoma (Figure 610) . . . . . Monomorium aithoderum


 * In profile, promesonotum evenly rounded anteriad, more-or-less straight posteriad, metanotal groove broad but shallow, often with distinct lateral cross-ribs; promesonotum elongate; eye commonly reniform, larger (eye width 2× greatest width of antennal scape); erect setae often present on mesosoma in SWBP specimens (Figure 611) . . . . . Monomorium stictonotum

12
return to couplet #10 (pt.)
 * Eye moderate (eye width 1–1.5 × greatest width of antennal scape), oval (most workers) to slightly elongate (some bright yellow workers); viewed in profile, promesonotum flattened and truncated; colour very variable; erect and suberect setae absent from head, mesosoma and nodes in all bright yellow workers,usually also absent in non-yellow workers (see Figures 604, 609) . . . . . Monomorium sydneyense


 * Eye large, (eye width ≥ 1.5 × greatest width of antennal scape), mostly elongate; viewed in profile, promesonotum often more elongate and rounded; colour always yellow (head may be slightly darker); erect or suberect setae usually present at least on petiole and postpetiole . . . . . 13

13
return to couplet #12
 * Eye very large (eye width ≥ 2 × greatest width of antennal scape), mesopleural sector of promesonotum and propodeum with strong microreticulate sculpture; erect and suberect setae (if present) restricted to nodes (Figure 612) . . . . . Monomorium micula


 * Eye smaller (eye width ≈ 1.5 × greatest width of antennal scape); mesopleural sector of promesonotum and propodeum lacking strong sculpture, cuticle relatively smooth and shining; erect and suberect setae often present on head and mesosoma (workers in many northern populations with conspicuous, erect humeral setae, but other raised setae lacking on promesonotum) (Figure 613) . . . . . Monomorium disetigerum

14
return to couplet #7
 * Yellowish-brown to dark brown in all SWBP populations (if yellowish-brown, then head and gaster darker); propodeum relatively short and usually smoothly rounded (Figure 614); eye compact and ovate . . . . . Monomorium fieldi


 * Uniformly yellow or yellow with first tergite of gaster also yellow, remaining tergites yellow-brown; propodeum usually relatively elongate (Figure 615); eye in larger specimens tending to large and elongate . . . . . Monomorium laeve

15
return to couplet #4
 * Number of mandibular teeth and denticles three . . . . . Monomorium rothsteini


 * Number of mandibular teeth and denticles four to seven . . . . . 16

16
return to couplet #15
 * Eye much longer than wide, either distinctly elongate (Figure 616) coming to a point anteriad, or reniform (Figure 617); worker small (HW usually < 0.60 mm); brown or dark brown species . . . . . 17


 * Eye circular, subcircular, weakly elongate (not coming to a point anteriad), elliptical or ovoid (e.g. Figure 618); worker usually larger (HW mostly > 0.60 mm) . . . . . 18

17
return to couplet #16
 * Eye elongate, reaching almost to mandible (Figure 616); mesosoma, propodeum and petiole strongly microreticulate; pilosity on promesonotum and propodeum consisting of dense, short setae; colour uniform dark brown . . . . . Monomorium anthracinum


 * Eye reniform (Figure 617); microreticulation on body surface less marked, and confined to lower mesopleuron and propodeum, otherwise smooth and shining; pilosity consisting of sparse, erect and suberect setae; colour brown or tawny orange with dark brown gaster . . . . . Monomorium megalops

18
return to couplet #16
 * Petiolar node long and low, barrel-shaped (Figure 619) . . . . . 19


 * Petiolar node not as above (usually cuboidal, conical, cuneate or tumular) . . . . . 20

19
return to couplet #18
 * Head capsule trapezoidal in full-face view, narrowest at vertex (Figure 620); frons longitudinally striate with combination of appressed setulae and erect and suberect setae; promesonotal sculpture in form of microreticulation, striolae and striae on mesopleuron, and striolae on posterodorsal surface; head orange, mesosoma, petiole and postpetiole dark brown to black, gaster bright yellow, legs brown . . . . . Monomorium flavonigrum


 * Head capsule rectangular in full-face view (Figure 621); frons longitudinally striate and reticulate with combination of incurved decumbent and subdecumbent setulae and erect and suberect setae; promesonotal sculpture in form of microreticulation and rugosity over entire promesonotum; otherwise coloured (usually a combination of a tawny or red head and mesosoma with some brown infuscation, and dark brown or black gaster) . . . . . Monomorium longinode

20
return to couplet #18
 * Anteromedial margin of clypeus a broadly U-shaped cleft between the median clypeal carinae, which are often produced as teeth, denticles or lobes (includes polymorphic species with disproportionately large, square heads in major caste; generally matt in appearance with rugose mesosoma) (Figure 622) . . . . . 21


 * Anteromedial margin of clypeus either convex and protuberant, straight, slightly emarginate, or with shallow V-shaped groove (e.g. Figures 623, 624, 625); at most, median clypeal carinae (if present) produced as weak lobes or denticles (includes mainly dry and wet sclerophyll forest species, often smooth and shining in appearance) . . . . . 32

21
return to couplet #20
 * Petiolar node cuboidal or nearly so, about as high as wide (Figure 626) . . . . . 22


 * Petiolar node conical (Figure 627), cuneate (Figure 628) or tumular (Figure 629), usually tapered dorsally, but in profile always higher than wide . . . . . 25

22
return to couplet #21
 * Propodeum armed with small denticles . . . . . Monomorium longiceps (in part, also see couplet couplet #28)


 * Propodeum unarmed . . . . . 23

23
return to couplet #22
 * Frons and mesosoma shining and polished in appearance with scattered foveae and striolae; distinct lateral striae present on propodeum; median clypeal carinae raised and distinct, produced as blunt lobes (Figure 630); petiolar node rugose . . . . . Monomorium xantheklemma


 * Frons and mesosoma matt in appearance, with promesonotum, propodeum and petiole either rugose or granulose-reticulate; clypeal carinae developed as stout, incurved denticles or teeth (Figure 631) . . . . . 24

24
return to couplet #23
 * Frons longitudinally striate; promesonotum microreticulate and rugose; red or reddish-orange; posterior promesonotum, propodeum, petiole and postpetiole strongly infuscated with black . . . . . Monomorium legulum


 * Frons finely granulose-microreticulate and striolate; promesonotum finely granulose-microreticulate; concolorous reddish-orange, without infuscation . . . . . Monomorium bihamatum

25
return to couplet #21
 * Frons densely foveate and microreticulate (Figure 632a); propodeal declivity strongly delimited anteriad by bevelled surface with well-defined anterior border (Figure 632b) . . . . . 26


 * Frons not foveate, propodeal declivity not as above . . . . . 27

26
return to couplet #25
 * Head and mesosoma without erect or semi-erect setae; colour uniformly orange . . . . . Monomorium elegantulum


 * Head and mesosoma with a few erect and semierect setae (Figure 633); brownish to black head and gaster, tan mesosoma (Eneabba only) . . . . . Monomorium falcatum gp. sp. JDM 1178

27
return to couplet #25
 * Head, mesosoma and gaster covered with decumbent setulae only, erect and suberect setae lacking; small (TL ≈ 2 mm) . . . . . Monomorium pubescens


 * Erect and suberect setae always present on body; larger (TL > 2 mm). . . . . . 28

28
return to couplet #27
 * Head capsule rectangular; usually five teeth and denticles, rarely four; monomorphic; colour tawny orange or red, often with some infuscation around propodeum, petiole and postpetiole, gaster orange, appendages brown. . . . . . Monomorium longiceps (in part, also see couplet couplet #22)


 * Head capsule square and massive; always with four stout teeth; monomorphic, polymorphic or displaying monophasic allometry; colour variable . . . . . 29

29
return to couplet #28
 * Monomorphic; colour predominantly orange or red . . . . . 30


 * Polymorphic or displaying monophasic allometry, with considerable size range between largest and smallest workers; colour variable but black, brown, black-and-orange and black-and-red predominate . . . . . 31

30
return to couplet #29
 * Anteromedial margin of clypeus with two broad, longitudinally striate lobes (Figure 634a); frons longitudinally striate with erect and suberect setae, setae short (≤ width of eye); propodeum rounded, transversely striate (Figure 634b); crimson to orange . . . . . Monomorium striatifrons


 * Median clypeal carinae produced apically as pair of pronounced teeth; frons microreticulate and striolate with erect and suberect setae; propodeum smoothly rounded or angulate in profile or armed with small denticles or flanges, but without transverse striae; crimson to reddish orange with head, gaster and appendages darker (rare and localised in north of SWBP) . . . . . Monomorium majeri

31
return to couplet #29
 * Smallest minor workers dissimilar in morphology and pilosity to media and major workers; major workers rather hirsute and rugose, minor workers with shorter setae and more angulate, microreticulate propodeum; typically among major and media workers head, gaster and appendages black, dark brown or brown, mesosoma, propodeum and waist segments orange to crimson; minor workers similar in colour, or uniformly brown or dark brown; median clypeal carinae produced as single pair of lobes or denticles in major and minor workers, occasionally feebly bilobate in media workers. (Possibly a complex of two or more species is represented here.) . . . . . Monomorium rufonigrum


 * Morphology of minor, media and major workers similar, colouration never as above in major and media workers (usually either concolorous orange, brown or black, or brown with yellow gaster); median clypeal carinae always produced as bifurcated lobes or denticles . . . . . Monomorium bicorne

32
return to couplet #20
 * Viewed in profile, postpetiole a curved, horizontal cone, narrowest at its junction with petiole and widest at or near its junction with gaster (Figure 635) . . . . . Monomorium crinitum


 * Viewed in profile, postpetiole strongly constricted both anteriad and posteriad, so that its greatest diameter is at its midpoint; postpetiolar shape round or square (Figure 636) . . . . . 33

33
return to couplet #32
 * Subpetiolar process a broad flange ending in a spur anteriad; propodeal angles produced in the form of sharp spines (Figure 637); three larger teeth and four tiny denticles on inner mandibular edge . . . . . Monomorium sublamellatum


 * Subpetiolar process at most a tapering, narrow flange ending in a small, anteroventral protuberance or spur; propodeal angles not produced as spines (e.g. Figure 638); maximum number of mandibular teeth and denticles five . . . . . 34

34
return to couplet #33
 * PF 1,2; small (HML 1.25–1.75 mm); four mandibular teeth and denticles; frons of head capsule and petiolar node unsculptured, smooth and shining, propodeal angles rounded . . . . . Monomorium sordidum


 * PF 2,2 or 2,3; size often larger, if small with four mandibular teeth and denticles, head and petiolar node distinctly sculptured or propodeal angles acute to denticulate . . . . . 35

35
return to couplet #34
 * Dorsum of head and entire mesosoma finely reticulate-punctate (Figure 639); PF 2,2 (introduced orange or yellow species, only found in highly disturbed, predominantly urban environments in Australia) . . . . . Monomorium pharaonis


 * Sculpture not as above, species generally smooth; PF predominantly 2,3 . . . . . 36

36
return to couplet #35
 * Frons with strong reticulate or foveate sculpture; propodeal declivity strongly delimited anteriad by oblique, bevelled surface with well-defined anterior border (Figure 640); viewed dorsally, mesosoma uniformly densely sculptured with longitudinal striae, reticulations and occasional foveae (Figure 641) . . . . . Monomorium lacunosum


 * Frons with reduced sculpture (not as above) or completely smooth and shining; propodeal declivity without distinct oblique, beveled surface with well-defined anterior border; sculpture of mesosoma not as above . . . . . 37

37
return to couplet #36
 * Basal tooth much broader than other pre-apical teeth (Figure 642); distinctly polymorphic, with large headed major workers having rather small eyes . . . . . Monomorium euryodon


 * Basal tooth of same size or smaller than other pre-apical teeth; worker monomorphic or exhibiting monophasic allometry . . . . . 38

38
return to couplet #37
 * Frons and promesonotum with many evenly-spaced short (nearly all ≤ width of eye) erect and suberect setae (Figure 643) . . . . . Monomorium brachythrix


 * Pilosity consisting mainly of longer erect and suberect setae (> width of eye), setation less dense . . . . . 39

39
return to couplet #38
 * PF 2,2; mandible with four teeth and denticles; often only three visible; propodeum unarmed (introduced species in urban or otherwise disturbed habitats) . . . . . Trichomyrmex destructor


 * PF 2,3; four teeth always visible, five often present; propodeum usually angulate, propodeal angles often with denticles, especially in larger workers (M. centrale, M. leae) . . . . . 40

40
return to couplet #39
 * Anteromedial margin of clypeus often projecting as narrow ellipse or rectangle, sometimes slightly emarginate, but never forming a shallow groove (Figure 644); clypeal denticles or lobes absent; petiolar node usually cuneate or tumular, only rarely subcuboidal or cuboidal . . . . . Monomorium leae


 * Anteromedial margin of clypeus forming a shallow V-shaped groove between median clypeal carinae, which are developed as denticles (Figure 645); petiolar node cuboidal or subcuboidal . . . . . 41

41
return to couplet #40
 * Eye moderate in size (eye width 0.5–1.5 x greatest width of antennal scape); head capsule nearly always darker than promesonotum in full-face view, but never lighter in colour; petiolar node higher than wide and tending to subcuboidal (Figure 646); number of mandibular teeth and denticles usually five (minute basal denticle may occasionally be lacking) . . . . . Monomorium centrale


 * Eye large (eye width > 1.5 x greatest width of antennal scape); head capsule lighter coloured than promesonotum in full-face view; petiolar node low and cuboidal in shape (Figure 647); four mandibular teeth and denticles (very rare) . . . . . Monomorium durokoppinense