Key to Micronesian Ants

This worker key is based on: [[Media:Clouse 2007a.pdf|Clouse, R. M. 2007. The Ants (Hymenoptera: Formicidae) of Micronesia. Micronesica. 39(2): 171–296. PDF]]

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List of Micronesia Ant species

1

 * Body with two isolated segments (the petiole and postpetiole) between mesosoma and gaster (Fig. 1C) . . . . . 2


 * Body with one isolated segment between mesosoma and gaster (the petiole), its separation from the gaster being a narrow constriction (Fig. 1A–B) . . . . . 3


 * Body with one isolated segment between mesosoma and gaster that is broadly attached to the first segment of the gaster (Fig. 9B) (Amblyoponinae) . . . . . 66

2
return to couplet #1
 * Frontal carinae close and vertical, such that antennal insertions are completely visible from above; pygydium flattened and bordered by tiny denticles (Fig. 3B–C) (Cerapachyinae) . . . . . 4


 * Frontal carinae usually covering antennal insertions such that they are at most only partly visible from above; pygydium simple (Myrmicinae) . . . . . 5

3
return to couplet #1
 * Sting present (Ponerinae) . . . . . 67


 * Sting absent . . . . . 85

4
return to couplet #2
 * With prominent eyes (Fig. 3B) . . . . . Cerapachys sp. 91952


 * Without eyes . . . . . Cerapachys biroi

5
return to couplet #2
 * Antennae with 7 or fewer segments . . . . . 6


 * Antennae with more than 7 segments . . . . . 14

6
return to couplet #5
 * Antennae with 7 segments (Fig. 1C) . . . . . Eurhopalothrix procera


 * Antennae with 6 or fewer segments . . . . . 7

7
return to couplet #6
 * Mandibles compact and triangular; labial shield without extended lateral margins (never T-shaped); inner margins of mandibles lined with teeth (Fig. 11B) . . . . . 8


 * Mandibles long and thin; labial shield with extended lateral margins, making the whole sclerite T-shaped; teeth only at ends of the mandibles (Fig. 11C) . . . . . 9

8
return to couplet #7
 * Eyes present; head with a single, long hair projecting laterally from each side, immediately above end of the antennal scrobe (Fig. 11A) . . . . . Strumigenys karawajewi


 * Eyes tiny, almost completely missing; head without single, distinct hair projecting laterally from each side . . . . . Strumigenys membranifera

9
return to couplet #7
 * Antennae with 4 segments . . . . . Strumigenys emmae


 * Antennae with 6 segments . . . . . 10

10
return to couplet #9
 * When view from above, mandibles with 3 apical teeth, the middle one shorter than other two (Fig. 11C) . . . . . Strumigenys rogeri


 * Mandibles with 2 apical teeth . . . . . 11

11
return to couplet #10 spongy substance (Fig. 11D) . . . . . 12
 * Posterior propodeum to anterior gaster covered with a light-colored,


 * Without spongy material (Fig. 11E) . . . . . Strumigenys szalayi

12
return to couplet #11
 * Combining the following: Mesosoma with little or no sponge, most sponge concentrated on the ventral side of the petiolar node and postpetiole; conspicuous standing hairs on the mesonotum consisting of a short pair on the pronotum and mesonotum . . . . . Strumigenys mayri


 * Not as above . . . . . 13

13
return to couplet #12
 * HL around 0.7 mm; curved, erect hairs on head long and spaced about as far apart as their length; spongiform bodies on propodeum forming two distinct ridges from the propodeal spines down to the petiolar insertion; the inner margin of the mandibles straight, base of subapical tooth joining base of end tooth, with no straight section of mandible separating the two (Fig. 11E) . . . . . Strumigenys godeffroyi


 * HL usually less than 0.5 mm; curved, erect hairs on head spaced closer together than their length; two pairs of extremely long hairs often missing; spongiform bodies on propodeum disorganized and not covering propodeal spines; inner margin of mandibles continuously curved, the subapical tooth separated from the base of the end tooth by a section of mandible longer than the subapical tooth’s length . . . . . Strumigenys frivaldszkyi

14
return to couplet #5
 * Postpetiole attached to dorsal surface of the gaster; small yellow ants . . . . . 15


 * Postpetiole attached to anterior end of the gaster, the gaster not noticeably suspended below the postpetiole; size and color variable . . . . . 16

15
return to couplet #14
 * Dorsal edge of each propodeal spine with a stout hair (Fig. 3D) . . . . . Crematogaster biroi cf.


 * Dorsal edge of each propodeal spine without a stout hair (Fig. 3E) . . . . . Crematogaster fritzi

16
return to couplet #14
 * Pronotum, mesonotum, and propodeum each bearing a pair of long spines; workers distinctly dimorphic . . . . . Pheidole sexspinosa


 * Lacking spines on the mesosoma as described above; workers monomorphic, polymorphic, or dimorphic . . . . . 17

17
return to couplet #16
 * Body surfaces, except for tarsi, funiculi, and mandibles covered with evenly spaced paddle-like hairs; antennae 12-segmented . . . . . Calyptomyrmex


 * Paddle-shaped hairs usually absent, or, if present, not covering all body surfaces as described above; antennal segment number variable . . . . . 18

18
return to couplet #17
 * Large, plate-like keel on the ventral surface of petiole; propodeum without spines (Fig. 15D) . . . . . 19


 * Ventral petiole without a large, plate-like keel; propodeum often with spines or blunt projections . . . . . 24

19
return to couplet #18
 * HW and HL more than 0.65 mm (up to 0.875 mm) . . . . . 20


 * HW 0.37–0.55 mm, HL 0.47–0.62 mm . . . . . 21

20
return to couplet #19
 * Head and mesosoma covered with thick, smooth, wavy, striate sculpture, giving a wrinkled appearance; HW 0.68 mm; HL 0.76 mm (Fig. 15A) . . . . . Vollenhovia mwereka


 * Head and mesosoma not sculptured as above (not wrinkled in appearance and with smooth patches on dorsum); head square in front view, both HW and HL about 0.8 mm . . . . . Vollenhovia oblonga

21
return to couplet #19
 * Area behind eyes distincly striate (Fig. 14C); middle part of frons punctate; HW 0.42–0.45 mm; HL 0.52–0.55 mm, CI = 81–86 (Fig. 14D) . . . . . 22


 * Area behind eyes smooth (Fig. 15C); middle part of fronts striate or smooth; head either smaller (and usually narrower) or larger and more square . . . . . 23

22
return to couplet #22
 * Mesosoma completely punctate (Fig. 15D); body dark brown . . . . . Vollenhovia kaselela


 * Central propodeal dorsum and anterior pronotum with smooth patches; body orangish brown . . . . . Vollenhovia sp. 6041940

23
return to couplet #21
 * Antennae 11-segmented; HW 0.37–0.41 mm (Fig. 15B); mesosoma mostly punctate, except for smooth patch on central anterior pronotum . . . . . Vollenhovia pwidikidika


 * Antennae 12-segmented; HW 0.55 mm (Fig. 14B); Mesosoma with smooth areas on dorsal and lateral propodeum and promesonotum . . . . . Vollenhovia sp. 23031948

24
return to couplet #18
 * Head with a prominent carina on each side that runs below eye from base of the mandibles to posterior corner of the head (Fig. 5C–D) . . . . . Myrmecina sp. 7121952


 * Head without such a carina . . . . . 25

25
return to couplet #24
 * Antennae with 10 segments, with the last 2 forming a conspicuous club . . . . . 26


 * Antennae with 9, 11 or 12 segments . . . . . 27

26
return to couplet #25
 * Eyes tiny; area around propodeal spiracle shining; workers monomorphic . . . . . Solenopsis papuana


 * Maximum eye diameter about equal to antennal club width; area around propodeal spiracle dull in larger workers; workers polymorphic . . . . . Solenopsis geminata

27
return to couplet #25
 * Clypeus forming a flange or shelf above the mandibles . . . . . 28


 * Clypeus completing the overall curve of the head to the mouth . . . . . 33

28
return to couplet #27
 * Mesosoma sculptured but lacking teeth, corners, or spines; anterior clypeal border extended forward as a distinctive, narrow, rectangular lobe; antennal scrobes large and deep, partly concealed by broad, downwardly-curving frontal carinae . . . . . Metapone truki


 * Mesosoma glossy and with teeth, corners, or spines; clypeus projecting outward to form an acutely cornered shelf above the mandibles; antennal scrobes shallow, not concealed by carinae (Fig. 10A–C) . . . . . 29

29
return to couplet #28
 * Head and mesosoma with strong, coarse, reticulate sculpture; propodeal spines as long as the petiole . . . . . Pristomyrmex punctatus


 * Reticulate sculpture absent and propodeal spines shorter than the petiole . . . . . 30

30
return to couplet #29
 * Sharp teeth on the pronotum . . . . . 31


 * Sharp pronotal teeth absent . . . . . 32

31
return to couplet #30
 * Pronotal spines nearly as large as the propodeal spines and clearly projecting upwards above the dorsal surface in side view (Fig. 10C) . . . . . Pristomyrmex quadridens


 * Pronotal spines notably shorter than the propodeal spines and projecting laterally, often not altering the outline of dorsal pronotum in side view . . . . . Pristomyrmex minusculus

32
return to couplet #30
 * Propodeal spines only about half length of postpetiole; deep, well-defined pits on head, especially laterally between eyes and mandibles; dark brown species (Fig. 10B) . . . . . Pristomyrmex levigatus


 * Propodeal spines about as long as length of postpetiole; head with shallow pits only; orange species (Fig. 10A) . . . . . Pristomyrmex largus

33
return to couplet #27
 * Antennal insertions in deep pit, the walls of which are formed by the fused rear clypeus and frontal lobes (Figs. 12B, 12D, 13B, 14A) . . . . . 34


 * Antennal insertions not in deep pit . . . . . 41

34
return to couplet #33
 * Antennae 11-segmented . . . . . 35


 * Antennae 12-segmented . . . . . 36

35
return to couplet #34 (Fig. 12B). . . . . Tetramorium sp. 14121952
 * Head and mesosoma with distinct, widely spaced, longitudinal and loosely reticulate sculpturing; frons and most of head with longitudinal sculpturing only; petiolar node smooth, shiny, and nearly square in profile


 * Mesosoma with deep reticulate sculpturing, head with reticulate sculpturing at vertex; petiolar node sculptured and rounded in profile (Fig. 13E, 14A) . . . . . Tetramorium smithi

36
return to couplet #34
 * Anterior edge or the dorsal pronotum with four evenly-spaced, stout hairs that are shorter than the spaces between them (Fig. 13C) . . . . . Tetramorium simillimum


 * Anterior dorsal pronotal hairs numbering more than four and longer than the spaces between them . . . . . 37

37
return to couplet #36
 * Hairs plumose, giving mesosoma fuzzy appearance (Fig. 13A, B) . . . . . Tetramorium lanuginosum


 * Mesosoma not fuzzy . . . . . 38

38
return to couplet #37
 * Mandibles with longitudinal striations . . . . . 39


 * Mandibles smooth or only weakly pitted . . . . . 40

39
return to couplet #38
 * Petiolar node quadrate; sculptured middle ridge of the frons distinct and cleanly split into two ridges that run parallel to each other at a point even with eyes, then rejoining before clypeus (Fig. 12C); dorsal propodeal spines longer than the height of the median peduncle by about half this height, about twice as long as ventral propodeal spines . . . . . Tetramorium bicarinatum


 * Petiolar node rounded in profile; middle ridge of frons indistinct, mixed with dense reticulate sculpturing, not temporarily split at level of eyes; dorsal propodeal spines equal to height of median peduncle and only slightly longer than ventral propodeal spines (Fig. 13F) . . . . . Tetramorium tonganum

40
return to couplet #38
 * First gastral tergite with basal costulae (rounded ridges) . . . . . Tetramorium pacificum


 * First gastral tergite without basal costulae . . . . . Tetramorium insolens

41
return to couplet #33
 * Combining the following: Clypeus with two longitudinal carinae; propodeum smoothly rounded lacking teeth or spines; last 3 segments of the antennae forming a distinct club . . . . . 42


 * Not with the above combination of characters . . . . . 47

42
return to couplet #41
 * Maximum diameter of the eyes more than half the width of the antennal club . . . . . 43


 * Maximum diameter of the eyes less than half the width of the antennal club . . . . . 46

43
return to couplet #42
 * Dorsal surface of head finely and evenly sculptured, dull . . . . . Monomorium pharaonis


 * Head shiny . . . . . 44

44
return to couplet #43
 * Terminal antennal segment about as long as preceding two combined; gaster dark brown to black, other parts of body yellow-brown . . . . . Trichomyrmex destructor


 * Terminal antennal segment distinctly longer than the combined length of previous two; coloration variable . . . . . 45

45
return to couplet #44
 * Petiole, including peduncle, longer than tall (Fig. 4F); dorsal pronotum distinctly lighter than the vertex of head . . . . . Monomorium floricola


 * Petiole, including peduncle, only about as long as tall (Fig. 4E); concolorous dark . . . . . Monomorium chinense-group

46
return to couplet #42
 * Mesepisternum smooth and shiny; propodeal angles broad, about 140 degrees (Fig. 5A) . . . . . Syllophopsis australica


 * Mesepisternum with coarse, reticulate sculpturing that gives it a dull appearance; propodeal angles steep, about 100 degrees (Fig 5B) . . . . . Syllophopsis sechellensis

47
return to couplet #41
 * Dorsal mesosoma without standing hairs . . . . . 48


 * Dorsal mesosoma with standing hairs . . . . . 52

48
return to couplet #47
 * Mesosoma in profile with distinct dorsal furrow separating propodeum from promesonotum; propodeal spines long and thin, about as long as the height of petiolar node peduncle (Fig. 3A); head and mesosoma yellow-orange, gaster dark brown . . . . . Cardiocondyla obscurior


 * Mesosoma smooth and continuous or with only a hint of a metanotal groove; propodeal spines not as long; head and gaster dark brown . . . . . 49

49
return to couplet #48
 * Postpetiolar sternite convex; maximum height of petiole about equal to maximum height of postpetiole . . . . . Cardiocondyla nuda


 * Postpetiolar sternite nearly flat; maximum height of petiole greater than maximum height of postpetiole . . . . . 50

50
return to couplet #49
 * Propodeal spines short and blunt; head, mesosoma, and gaster overall dark brown, the gaster only slightly darker . . . . . Cardiocondyla kagutsuchi


 * Propodeal spines distinct and pointed; mesosoma clearly lighter than gaster and head . . . . . 51

51
return to couplet #50
 * Metanotal groove absent but suggested by a slight impression in the mesosomal profile; mesosoma orange to warm yellow, and gaster black to dark brown . . . . . Cardiocondyla tjibodana


 * Metanotal groove completely absent, dorsal mesosoma flat or convex in profile; mesosoma yellow to brown, but without an orange or warm hue, and gaster black to dark brown . . . . . Cardiocondyla minutior

52
return to couplet #47
 * Combining the following: Petiole lacking anterior peduncle; frontal carinae elongate; antennal scrobes present; propodeum with thick, long (0.3 mm or longer) spines . . . . . 53


 * Petiole with anterior peduncle; frontal carinae indistinct and shorter than half the length of antennal scape; antennal scrobes weak or absent; propodeum with or without spines, but if with spines, less than 0.3 mm . . . . . 56

53
return to couplet #52
 * Propodeal spines approximately 0.5 mm long; pronotum flattened and marginate anteriorly and laterally . . . . . Romblonella palauensis


 * Propodeal spines 0.3 mm long; pronotum not marginate as described above . . . . . 54

54
return to couplet #53
 * Mesosomal dorsum with fine, reticulate sculpturing . . . . . 55


 * Mesosomal dorsum sculpturing predominately shallow longitudinal rugulae and coarse reticulations . . . . . Romblonella yapensis

55
return to couplet #54
 * Propodeal spines straight or very slightly curved at most; head dark brown, remainder of body light brown . . . . . Romblonella townesi


 * Propodeal spines distinctly curved; coloration of head, mesosoma, petiole, postpetiole, and gaster black . . . . . Romblonella sp. 6051940

56
return to couplet #52
 * Antennae nine-segmented and with a two-segmented club . . . . . Carebara atoma


 * Antennae 12-segmented, clubbing variable . . . . . 57

57
return to couplet #56
 * Antennae lacking apical club or appearing to have an indistinct four-segmented club; mesosoma generally smooth and shiny except for strongly punctate mesopleuron . . . . . Aphaenogaster osimensis


 * Antennae with three-segmented apical club, indistinctly only in Rogeria sp. 25111995; mesosomal sculpturing variable . . . . . 58

58
return to couplet #57
 * Mesosomal profile smooth and more or less evenly convex, interrupted only by a small, notch-like metanotal groove . . . . . 59


 * Mesosomal profile concave in profile, dropping between pronotum and propodeum . . . . . 60

59
return to couplet #58
 * Dorsal propodeum between and anterior to propodeal spines coarsely punctate . . . . . Rogeria stigmatica


 * Dorsal propodeum between and anterior to propodeal spines smooth and shining . . . . . Rogeria sp. 25111995

60
return to couplet #58
 * Pronotal dorsum sculptured, not smooth and shining . . . . . 61


 * Pronotal dorsum smooth and shining . . . . . 63

61
return to couplet #60
 * Entire mesosoma of minors with deep, reticulate sculpturing (Fig 7A, B); (majors unknown) . . . . . Pheidole sp. 24041958


 * Entire mesosoma of minors with punctate sculpturing (Fig. 8B); majors with mostly punctate sculpturing, except for small smooth areas . . . . . 62

62
return to couplet #61
 * Majors: Frontal carinae short: punctate sculpturing near eyes blending with linear sculpturing between antennae; entire mesosoma mostly punctured, even under reticulate sculpturing, except for small patches under the pronotal protuberances; Majors and minors: entire body reddish brown to orange. Minors: dorsal propodeum fairly flat in profile . . . . . Pheidole nindi


 * Majors: Frontal carinae long, clearly separating punctate sculpturing near eyes from linear sculpturing between antennae; mesosoma mostly covered in punctate sculpturing, although reticulate sculpturing on pronotum and smooth patches on lateral pronotum and mesosoma distinct; Majors and minors: entire body blackish orange to ashy brown. Minors: dorsal propodeum convex in profile . . . . . Pheidole recondita

63
return to couplet #60
 * Pronotum and mesonotum fused to form the promesonotum; in minor workers, promesonotum shiny dorsally . . . . . 64


 * Pronotum and mesonotum separated by an impression that causes the mesonotum to look distinctly humped in side view, forming a separate section from pronotum and propodeum; mesonotum dull and sculptured dorsally . . . . . 65

64
return to couplet #63
 * Majors with a large, often blunt median hypostomal tooth, flanked closely by two teeth, one on each side (two lateral teeth, one each near the mandibular insertions, are also present but difficult to see); propodeal teeth of minors reduced to minute denticles . . . . . Pheidole umbonata


 * Major with two lateral hypostomal teeth (one each next to the mandibular insertions) only; minors with short but distinct propodeal teeth (Fig. 8A) . . . . . Pheidole megacephala

65
return to couplet #63
 * Majors: Area between eye and the antennal insertion with at least some reticulate sculpturing (Fig. 7C); dorsum of postpetiole mostly smooth and shining; majors and minors: propodeal spine horter than maximum width of propodeal spiracle (Fig. 7D) . . . . . Pheidole fervens


 * Majors: Area between eye and antennal insertion with longitudinal sculpturing only (Fig. 7E); dorsum of postpetiole mostly punctate, weakly shining; majors and minors: propodeal spine longer than maximum width of propodeal spiracle (Fig. 7F) . . . . . Pheidole oceanica

66
return to couplet #1
 * Entire body surface matte due to dense punctures . . . . . Prionopelta opaca


 * Body surface slightly shining due to weaker sculpturing . . . . . Prionopelta kraepelini

67
return to couplet #3
 * Mandibles long, falcate, and without teeth; pretarsal claws pectinate . . . . . Leptogenys falcigera


 * Mandibles and pretarsal claws not as above . . . . . 68

68
return to couplet #67
 * Mandibles long, slender, straight, bent sharply at apex (Fig. 1A) . . . . . 69


 * Mandibles short and more or less triangular . . . . . 71

69
return to couplet #68
 * Petiolar node with a single, sharp, apical spine . . . . . Odontomachus simillimus


 * Apex of petiolar node rounded or acute, but no spine present . . . . . 70

70
return to couplet #69
 * Dorsal surface of head and pronotum largely smooth and shining; petiolar apex acute in profile; head notably darker than remainder of body . . . . . Anochetus splendidulus


 * Median dorsal surface of head and usually rest of pronotal dorsum with conspicuous sculpture; petiolar apex rounded in profile; body and head concolorous, usually dark brown, although many specimens orange . . . . . Anochetus graeffei

71
return to couplet #68
 * Pretarsal claws with a single median tooth (Fig. 8C); petiolar node longer than wide when viewed from above; body nearly devoid of erect hairs; antennal insertions widely separated by broad clypeus; hind legs with 2 pectinate spurs at apex of tibia . . . . . Platythyrea parallela


 * Pretarsal claws simple; petiolar node usually broader or nearly as broad as long when viewed from above; body with erect hairs; antennal insertions closely approximated; tibial spurs not as above . . . . . 72

72
return to couplet #71
 * Apex of hind tibia with two spurs: a large pectinate spur behind a much smaller, simple spur . . . . . 73


 * Apex of hind tibia with one large pectinate spur . . . . . 75

73
return to couplet #72
 * Sides of pronotum with fine longitudinal striations . . . . . Brachyponera atrata


 * Sides of pronotum without striations . . . . . 74

74
return to couplet #73
 * In profile, mesosoma flat or weakly convex, propodeum continuous with promesonotum; mesopleuron rough and dull with various degrees of pilosity . . . . . Pseudoponera stigma


 * Mesosoma when viewed in profile with a distinct drop from mesonotum down to propodeum; mesopleuron smooth and shining, without hairs or sculpturing . . . . . Brachyponera luteipes

75
return to couplet #72
 * Compound eyes absent (Figs. 1B, 3F) . . . . . 76


 * Compound eyes present . . . . . 77

76
return to couplet #75
 * In profile, anterior face of petiole strongly concave while posterior face lightly convex (Figs. 1B, 4A); head and gaster with blackish-orange coloration . . . . . Cryptopone butteli


 * In profile, petiole with anterior and posterior faces sloping upward at nearly equal angles (Fig. 4B); body concolorous orange or head and gaster slightly darker . . . . . Cryptopone testacea

77
return to couplet #75
 * Ventral keel of petiole with a small translucent “window” and with two small teeth projecting posteriorly (Fig. 9A) . . . . . 78


 * Ventral keel of petiole simple, lobe-like, completely opaque . . . . . 82

78
return to couplet #77
 * Mesometanotal suture distinctly visible on dorsal mesonotum; antennae with a weak, five-segmented club; HW 0.36–0.40 mm . . . . . Ponera incerta


 * Mesometanotal suture absent from dorsal mesonotum; antennal club variable; HW usually larger or smaller . . . . . 79

79
return to couplet #78
 * Large species (HW 0.51–0.58); mesosoma dorsum with numerous erect hairs; antennal club indistinctly four- or five-segmented . . . . . Ponera loi


 * HW smaller; dorsal mesosoma lacking standing hairs; antennal club distinctly four-segmented . . . . . 80

80
return to couplet #79
 * Tiny species (HW 0.325 mm in single specimen); antennae with four-segmented club; anterior gaster with distinct corners when viewed from above (Fig 8E); overall color light orange-brown . . . . . Ponera sp. 10091995


 * HW 0.39–0.48 mm; gaster and antennal club not as above (Fig 8F); color orangish brown to dark brown . . . . . 81

81
return to couplet #80
 * Petiolar node wide (PNI 80–93); HW 0.43–0.48 . . . . . Ponera clavicornis


 * Petiolar node narrow (PNI 66–78), HW 0.39–0.45 . . . . . Ponera tenuis

82
return to couplet #77
 * Petiolar node tapering dorsally, and its height (not counting the ventral process) distinctly greater than length; mesepisternum usually smooth and outlined by a carina . . . . . 83


 * Anterior and posterior faces of petiolar node parallel, or if tapering slightly, then the height (not counting ventral process) nearly the same as the length; mesepisternum usually sculptured and fused with mesonotum . . . . . 84