Key to Monomorium of the southwestern Australian Botanical Province

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This worker key 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 2 PDF

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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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

3

return to couplet #2

  • PF 2,3; number of mandibular teeth 5; propodeum armed with sharp denticles . . . . . Monomorium decuria
Monomorium decuria casent0902301 h 1 high.jpg
Monomorium decuria casent0902301 p 1 high.jpg
Monomorium sydneyense casent0172359 head 1.jpg
Monomorium sydneyense casent0172359 profile 1.jpg

(pt.)

4

return to couplet #2

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
Figure 600.
  • 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
Figure 601.

6

return to couplet #5

Figure 602.
Monomorium eremophilum casent0902303 h 1 high.jpg
Monomorium eremophilum casent0902303 p 1 high.jpg
Figure 603.
Monomorium nanum casent0902316 h 1 high.jpg
Monomorium nanum casent0902316 p 1 high.jpg

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
Figure 604.
  • 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
Figure 606.
Monomorium arenarium casent0902291 h 1 high.jpg
Monomorium arenarium casent0902290 d 1 high.jpg
  • 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
Figure 607.

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
Monomorium silaceum casent0902323 h 1 high.jpg
Monomorium silaceum casent0902323 p 1 high.jpg
  • 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
Figure 608.
  • 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
Figure 609.

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
Figure 610.
Monomorium aithoderum casent0902287 h 1 high.jpg
Monomorium aithoderum casent0902287 p 1 high.jpg
  • 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
Figure 611.
Monomorium stictonotum casent0902324 h 1 high.jpg
Monomorium stictonotum casent0217890 p 1 high.jpg

12

return to couplet #10

  • 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
Figure 604.
Figure 609.
Monomorium sydneyense casent0172359 head 1.jpg
Monomorium sydneyense casent0172359 profile 1.jpg

(pt.)

  • 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
Figure 612.
Monomorium micula casent0902315 h 1 high.jpg
Monomorium micula casent0902315 p 1 high.jpg
  • 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
Figure 613.
Monomorium disetigerum casent0902302 h 1 high.jpg
Monomorium disetigerum casent0902302 p 1 high.jpg

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
Figure 614.
Monomorium fieldi casent0172355 head 1.jpg
Monomorium fieldi casent0172355 profile 1.jpg
  • 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
Figure 615.
Monomorium laeve casent0904588 h 1 high.jpg
Monomorium laeve casent0904588 p 1 high.jpg

15

return to couplet #4

Monomorium rothsteini casent0217889 h 1 high.jpg
Monomorium rothsteini casent0217889 p 1 high.jpg
  • 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
Figure 616.
Figure 617.
  • 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
Figure 618.

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
Figure 616.
Monomorium anthracinum F55.jpg
  • 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
Figure 617.
Monomorium megalops casent0902314 h 1 high.jpg
Monomorium megalops casent0902314 p 1 high.jpg

18

return to couplet #16

  • Petiolar node long and low, barrel-shaped (Figure 619) . . . . . 19
Figure 619.
  • 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
Figure 620.
Monomorium flavonigrum casent0902311 h 1 high.jpg
Monomorium flavonigrum casent0902311 p 1 high.jpg
  • 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
Figure 621.
Monomorium longinode casent0902313 h 1 high.jpg
Monomorium longinode casent0902313 p 1 high.jpg

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
Figure 622.
  • 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
Figure 623.
Figure 624.
Figure 625.

21

return to couplet #20

  • Petiolar node cuboidal or nearly so, about as high as wide (Figure 626) . . . . . 22
Figure 626.
  • Petiolar node conical (Figure 627), cuneate (Figure 628) or tumular (Figure 629), usually tapered dorsally, but in profile always higher than wide . . . . . 25
Figure 627.
Figure 628.
Figure 629.

22

return to couplet #21

Monomorium longiceps casent0217887 h 1 high.jpg
Monomorium longiceps casent0217887 p 1 high.jpg

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
Figure 630.
Monomorium xantheklemma casent0902326 h 1 high.jpg
Monomorium xantheklemma casent0902326 p 1 high.jpg
  • 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
Figure 631.

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
Monomorium legulum casent0902312 h 1 high.jpg
Monomorium legulum casent0902312 p 1 high.jpg
  • Frons finely granulose-microreticulate and striolate; promesonotum finely granulose-microreticulate; concolorous reddish-orange, without infuscation . . . . . Monomorium bihamatum
Monomorium bihamatum casent0902293 h 1 high.jpg
Monomorium bihamatum casent0902293 p 1 high.jpg

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
Figure 632a.
Figure 632b.
  • Frons not foveate, propodeal declivity not as above . . . . . 27

26

return to couplet #25

Monomorium elegantulum casent0902300 h 1 high.jpg
Monomorium elegantulum casent0902300 p 1 high.jpg
  • 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
Figure 633.

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
Monomorium pubescens casent0902320 h 1 high.jpg
Monomorium pubescens casent0902320 p 1 high.jpg
  • 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)
Monomorium longiceps casent0217887 h 1 high.jpg
Monomorium longiceps casent0217887 p 1 high.jpg
  • 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
Figure 634a.
Figure 634b.
Monomorium striatifrons casent0902325 h 1 high.jpg
Monomorium striatifrons casent0902325 p 1 high.jpg
  • 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
Monomorium majeri F54.jpg

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
Monomorium rufonigrum casent0902321 h 1 high.jpg
Monomorium rufonigrum casent0902321 p 1 high.jpg
  • 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
Monomorium bicorne F60.jpg
Monomorium bicorne F52.jpg

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
Figure 635.
Monomorium crinitum casent0902298 h 1 high.jpg
Monomorium crinitum casent0902298 p 1 high.jpg
  • 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
Figure 636.

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
Figure 637.
  • 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
Figure 638.

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
Monomorium sordidum casent0008624 head 1.jpg
Monomorium sordidum casent0008624 profile 1.jpg
  • 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
Figure 639.
Monomorium pharaonis casent0104095 head 1.jpg
Monomorium pharaonis casent0104095 profile 1.jpg
  • 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
Figure 640.
Figure 641.
  • 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
Figure 642.
Monomorium euryodon casent0902310 h 1 high.jpg
Monomorium euryodon casent0902310 p 1 high.jpg
  • 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
Figure 643.
Monomorium brachythrix casent0902294 h 1 high.jpg
Monomorium brachythrix casent0902294 p 1 high.jpg
  • 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
Monomorium destructor casent0008623 head 1.jpg
Monomorium destructor casent0008623 profile 1.jpg
  • 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
Figure 644.
Monomorium leae casent0008622 head 1.jpg
Monomorium leae casent0008621 profile 1.jpg
  • 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
Figure 645.

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
Figure 646.
Monomorium centrale casent0217884 h 1 high.jpg
Monomorium centrale casent0217884 p 1 high.jpg
  • 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
Figure 647.