Key to Proceratium workers of the world

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The following key is based on Baroni Urbani, C., de Andrade, M.L. (2003) The ant genus Proceratium in the extant and fossil record (Hymenoptera: Formicidae). Museo Regionale di Scienze Naturali, Monografie, 36, 1–492.


1

2

return to couplet #1

  • Propodeal dorsum with a swelling covered by short hairs only (Figs. 59, 63, 65) . . . . . 3
  • Propodeal dorsum without swelling and covered by short and long hairs . . . . . 6

3

return to couplet #2

  • Gaster sculptured only in the posterior half or less (Figs. 62, 65) . . . . . 5

4

return to couplet #3

  • Head and mesosoma reticulate-foveolate with superimposed granulation. Propodeal swelling broad and low. Ecuador . . . . . Proceratium ecuadoriense
  • Head and mesosoma granulate only. Propodeal swelling narrow and high. Colombia . . . . . Proceratium colombicum

5

return to couplet #3

  • Petiole 1/5 longer than broad. Postpetiole shorter than 1/2 of the gastral tergite I (LT4). Postpetiole and gaster more convex. Colombia . . . . . Proceratium catio
Head of Proceratium catio worker
Lateral view of Proceratium catio worker
  • Petiole at most 1/8 longer than broad. Postpetiole slightly longer than ½ of the gastral tergite I (LT4). Postpetiole and gaster less convex. Brazil . . . . . Proceratium brasiliense

6

return to couplet #2

  • Mid basitarsi with no hairs long 1/2 of the mid basitarsal length . . . . . 7
  • Mid basitarsi with at least one hair about 1/2 of the mid basitarsal length . . . . . 8

7

return to couplet #6

  • Postpetiole shorter than 1/2 of LT4. TL ≥ 3.70 mm. Dark ferruginous-brown. Dominican Republic . . . . . Proceratium taino

8

return to couplet #6

  • Area between the basal and declivous faces of the propodeum with a transversal carina angulate or denticulate laterally . . . . . 9
  • Area between the basal and declivous faces of the propodeum with at most very superficial traces of transversal carina . . . . . 10

9

return to couplet #8

Head of Proceratium mexicanum worker
Lateral view of Proceratium mexicanum worker
  • Postpetiole anterolaterally angulate. IGR > 0.23. TL < 2.5 mm. Dominican amber . . . . . Proceratium poinari

10

return to couplet #8

  • Mesosoma in profile gently convex. Postpetiole in dorsal view more convex and slightly angulate anterolaterally. Body sculpture more marked. (Fig. 67) Costa Rica, Mexico . . . . . Proceratium convexiceps
  • Mesosoma in side view more elongate. Postpetiole in dorsal view more rectangular and angulate anterolaterally. Body sculpture more superficial (Figs. 74, 78) . . . . . 11

11

return to couplet #10

  • TL< 3.60 mm. WL ≤ 0.95 mm. Honduras, Costa Rica, Panama, Colombia, Venezuela. Texas?, Edcuador? . . . . . Proceratium micrommatum
Lateral view of Proceratium micrommatum worker

12

return to couplet #1

  • Eyes composed by a single, large, convex facet (Fig. 43) . . . . . 13
  • Eyes absent or at most composed by an agglomeration of minute ommatidia (Fig. 98) . . . . . 24

13

return to couplet #12

  • Fore tibiae without thick basal spine (Fig. 155). Palp formula 3,2 . . . . . 14
  • Fore tibiae with a basal spine (Fig. 38). Palp formula 4,3 . . . . . 15

14

return to couplet #13

  • Clypeus surrounding the antennal socket, subrectangular and protruding anteriorly. Propodeal dorsum with a median swelling. Colombia . . . . . Proceratium transitionis
  • Clypeus not surrounding the antennal socket, reduced medially and triangular. Propodeal dorsum without swelling. Venezuela . . . . . Proceratium lattkei

15

return to couplet #13

  • Propodeal sides unarmed, convex in profile. Head, mesosoma, petiole and postpetiole foveolate . . . . . 16
  • Propodeal sides at least with a well marked angle, or a small tooth or spine . . . . . 17

16

return to couplet #15

  • Integumental foveae smaller (Fig. 36). Pilosity denser and shorter. Gaster convex in side view. IGR 0.27-0.29. Mauritius . . . . . Proceratium avium
Head of Proceratium avium worker
Lateral view of Proceratium avium worker
  • Integumental foveae larger (Fig. 37). Pilosity sparser and longer. Gaster in side view less convex. IGR 0.31-0.34. Mauritius . . . . . Proceratium avioide

17

return to couplet #15

  • Gastral tergite I greatly hypertrophied and projecting posteriorly (Fig. 34). Funicular joints slightly longer than broad. Madagascar . . . . . Proceratium diplopyx
Head of Proceratium diplopyx worker
Lateral view of Proceratium avium worker
  • Gastral tergite I round or angulate posteriorly; never projecting. Funicular joints broader than long . . . . . 18

18

return to couplet #17

  • Gastral tergite I angulate on the curvature (Fig. 48). Integument from head to gastral tergite I entirely foveolate. Sarawak . . . . . Proceratium foveolatum
Head of Proceratium foveolatum worker
Lateral view of Proceratium foveolatum worker
  • Gastral tergite I round on the curvature. IGastral tergite I at most punctate/reticulate . . . . . 19

19

return to couplet #18

20

return to couplet #19

  • Propodeal sides with an obtuse angle only. Ventral process of the petiole reduced or in shape of a very short triangle. Postpetiole about 1/4 shorter than first gastral tergite. Costa Rica . . . . . Proceratium goliath
  • Propodeal sides with a tooth. Ventral process of the petiole distinct and spiniform. Postpetiole about 1/7 shorter than the first gastral tergite. Mexico . . . . . Proceratium tio
Head of Proceratium tio worker
Lateral view of Proceratium tio worker

21

return to couplet #19

  • Standing hairs short (Figs. 32, 33). Propodeal sides at most toothed (Figs. 32, 33). Propodeal lobes without or at most with a narrow lamellaceous expansion . . . . . 22
  • Standing hairs longer (Figs. 39, 42). Propodeal sides spinose (Figs. 39, 42), only toothed in the smallest specimens of stictum. Propodeal lobes with broad lamellaceous expansions . . . . . 23

22

return to couplet #21

  • Postpetiole medially concave and laterally weakly lobate. Sculpture shallower. CI < 87. Australia (Northern Territory) . . . . . Proceratium cavinodus
Head of Proceratium cavinodus worker
Lateral view of Proceratium cavinodus worker
  • Postpetiole medially straight and laterally convex. Sculpture deeper. CI > 91. Proceratium boltoni
Head of Proceratium boltoni worker
Lateral view of Proceratium boltoni worker

23

return to couplet #21

  • Hind basitarsi longer, HTiL/HBaL ≥ 1.32. Cephalic sculpture superficial. Frontal carinae less divergent posteriorly. Australia (Queensland) . . . . . Proceratium stictum
Head of Proceratium stictum worker
Lateral view of Proceratium stictum worker
  • Hind basitarsi shorter, HTiL/HBaL ≤ 1.17. Cephalic sculpture deeper. Frontal carinae more divergent posteriorly. Borneo, Brunei, Malaysia (Sabah and Sarawak), Thailand and Singapore . . . . . Proceratium deelemani
Head of Proceratium deelemani worker
Lateral view of Proceratium deeelemani worker

24

return to couplet #12

25

return to couplet #24

26

return to couplet #25

  • Antennal socket surpassing the anterior border of the clypeus. Standing hairs suberect and present on the whole body including the antennae and the legs. Pakistan . . . . . Proceratium confinium
  • Antennal socket not surpassing the anterior border of the clypeus. Standing hairs subdecumbent or decumbent, rare on the antennae and absent from the legs. United States (California) . . . . . Proceratium californicum
Lateral view of Proceratium californicum worker

27

return to couplet #25

28

return to couplet #27

  • Head granulopunctate. Petiole slightly longer than broad. Second tarsomere of hind legs about as long as the pretarsus. Japan . . . . . Proceratium morisitai
Head of Proceratium morisitai worker
Lateral view of Proceratium morisitai worker
  • Head reticulopunctate. Petiole about as broad as long. Second tarsomere of hind legs about 1/5 longer than the pretarsus. Central and Southern Europe, Turkey . . . . . Proceratium melinum
Head of Proceratium melinum worker
Lateral view of Proceratium melinum worker

29

return to couplet #27

  • Mid basitarsi shorter than fore basitarsi. First gastral tergite strongly angulate on the curvature . . . . . 30
  • Mid basitarsi as long as or longer than the fore basitarsi. First gastral tergite convex or, at most weakly angulate . . . . . 31

30

return to couplet #29

  • Gaster short, opaque, with dense and short hairs (Fig. 92). United States . . . . . Proceratium pergandei
Head of Proceratium pergandei worker
Lateral view of Proceratium pergandei worker
  • Gaster long, shining, with sparse and long hairs (Fig. 99). United States . . . . . Proceratium chickasaw
Head of Proceratium chickasaw worker
Lateral view of Proceratium chickasaw worker

31

return to couplet #29

  • First funicular joint 1/2 longer than broad. Funicular joints 2-10 longer than broad. Gaster weakly angulate on the curvature . . . . . 32
  • First funicular joint at most 1/3 longer than broad. Funicular joints 2-10 about as broad as long. Gaster strongly convex but without angle on the curvature . . . . . 33

32

return to couplet #31

  • Scapes surpassing the vertexal margin. TL ≥ 5.5 mm. United States . . . . . Proceratium creek
Head of Proceratium creek worker
Lateral view of Proceratium creek worker
  • Scapes reaching the vertexal margin. TL < 5.0 mm. United States (Texas) and North Mexico . . . . . Proceratium compitale
Head of Proceratium compitale worker
Lateral view of Proceratium compitale worker

33

return to couplet #31

  • Propodeal lamellae absent. Head with sub-parallel sides. Body sculpture superficial. Malta and Sicily . . . . . Proceratium melitense
  • Propodeal lamellae well developed. Head strongly narrowing posteriorly. Body sculpture deeper . . . . . 34

34

return to couplet #33

  • Mesosoma, petiole and postpetiole deeply granulopunctate. Body dark ferrugineous. Japan, Korea (and China?) . . . . . Proceratium watasei
  • Mesosoma, petiole and postpetiole punctate. Colour light brown. Italy, Croatia, Greece, Algeria, Morocco and Tunisia . . . . . Proceratium algiricum

35

return to couplet #24

  • Frontal carinae very close to each other and posteriorly attached . . . . . 36
  • Frontal carinae far from each other and posteriorly diverging . . . . . 38

36

return to couplet #35

  • Head and mesosoma strongly and irregularly foveolate. Genal carinae strongly impressed. Propodeal lamellae developed. First gastral sternite flat. Postpetiole and first gastral tergite covered by foveae. Sabah . . . . . Proceratium microsculptum
Lateral view of Proceratium microsculptum worker
  • Head and mesosoma granulate. Genal carinae absent. Propodeal lamellae dabsent. First gastral sternite tooth-shaped and projecting anteriorly. Postpetiole and first gastral tergite without foveae . . . . . 37

37

return to couplet #36

38

return to couplet #35

  • Head, mesosoma, petiole and postpetiole covered by granulation only. Clypeus anteromedially with a triangular tooth. Posterior border of the first gastral tergite without macula visible in transparency . . . . . 39
  • Head, mesosoma, petiole and postpetiole never covered by granulation only. Clypeus anteromedially at most with a subround small tooth. Posterior border of the first gastral tergite with a clear macula visible in transparency . . . . . 41

39

return to couplet #38

Head of Proceratium bhutanense worker
Lateral view of Proceratium bhutanense worker

40

return to couplet #39

  • Propodeal sides at most with a narrow lamella surrounding the propodeal lobe only. Mid basitarsi with hairs shorter than 1/2 of the mid basitarsus length. Palp formula 4,3. Japan, Korea?, China? . . . . . Proceratium itoi
Head of Proceratium itoi worker
Lateral view of Proceratium itoi worker
  • Propodeal sides with a broad lamella on their whole length. Mid basitarsi with hairs 1/2 of the mid basitarsus length. Palp formula 3,2. Malaysia . . . . . Proceratium malesianum
Head of Proceratium malesianum worker
Lateral view of Proceratium malesianum worker

41

return to couplet #38

  • Lower mesopleura inflated (Figs. 121, 122, 124). Clypeus either with a small median subround projection or, if straight, minutely crenulate. Palp formula 3,2 or 4,3. Mandibular base without macula. Petiole with a neck . . . . . 42
  • Mesopleura never inflated (Figs. 139, 146, 159). Clypeus weakly concave or, if straight, never crenulate. Palp formula 2,2. Mandibular base with a light macula. Petiole without neck . . . . . 45

42

return to couplet #41

  • Mesosoma and petiole with very superficial traces of foveae. Petiolar dorsum postero-medially with a large, transparent blister below the integument. Lower mesopleurae entirely inflated. Palp formula 4,3. Israel . . . . . Proceratium galilaeum
  • Head, mesosoma, petiole, postpetiole and gaster with foveae variably impressed. Petiolar dorsum postero-medially with at most an irregular point. Lower mesopleurae inflated posteriorly only. Palp formula 3,2 . . . . . 43

43

return to couplet #42

  • Integumental foveae superficial. First gastral tergite longer than 1/4 of the postpetiole. Zimbabwe . . . . . Proceratium arnoldi
Head of Proceratium arnoldi worker
Lateral view of Proceratium arnoldi worker
  • Integumental foveae deep. First gastral tergite short, 1/7 or less of the postpetiole . . . . . 44

44

return to couplet #43

Head of Proceratium burundense worker
Lateral view of Proceratium burundense worker
  • Integumental foveae large and deep. Gastral sculpture deep (Fig. 121). Cameroon . . . . . Proceratium lunatum
Head of Proceratium lunatum worker
Lateral view of Proceratium lunatum worker

45

return to couplet #41

  • Petiole in profile triangular and clearly narrowing apically (Figs. 126,

127) . . . . . 46

  • Petiole in profile rectangular (Figs. 141, 148) . . . . . 47

46

return to couplet #45

  • Lateral expansions of the frontal carinae broad and far from each other. Head with dense punctures (Fig. 126). SI > 76. TL > 4.5 mm. Fiji Islands . . . . . Proceratium relictum
Head of Proceratium relictum worker
Lateral view of Proceratium relictum worker
  • Lateral expansions of the frontal carinae narrow and close each other. Head with sparse punctures (Fig. 127). SI < 73. TL < 3.7 mm. Fiji Islands . . . . . Proceratium oceanicum
Head of Proceratium oceanicum worker
Lateral view of Proceratium oceanicum worker

47

return to couplet #45

  • Postpetiole concave and laterally lobate in dorsal view. Posterior border of first gastral tergite with a fold. Head, mesosoma, petiole, postpetiole and gaster strongly sculptured. First gastral tergite with traces of longitudinal rugostties . . . . . 48
  • Postpetiole in dorsal view neither concave nor laterally lobate. Posterior border of first gastral tergite not folded. Head, mesosoma, petiole, postpetiole and gaster less strongly sculptured. First gastral tergite without traces of longitudinal rugosities . . . . . 49

48

return to couplet #47

  • Frontal area at least 1/3 of the head width. Propodeal sides with at most a small denticle. Rugosities on the first gastral tergite irregular and thin (Fig. 146). SI < 65. Sarawak . . . . . Proceratium angulinode
  • Frontal area about 1/4 of the head width. Propodeal sides with a broad, lamelliform tooth. Rugosities on the first gastral tergite regular and thick (Fig. 147). SI > 74. Sarawak . . . . . Proceratium striativentre

49

return to couplet #47

50

return to couplet #49

  • TL ≥ 2.37 mm if the TL approaches 2.3 mm, (papuanum specimens can vary between 2.37-2.59 mm), then the frontal area about 1/3 of HW . . . . . 52

51

return to couplet #50

  • Head and mesosoma with marked reticulation. Petiole more than 1 and 1/2 broader than long. CI ≥ 100. Papua New Guinea . . . . . Proceratium snellingi
  • Head and mesosoma with superficial punctures. Petiole 1 and 1/2 broader than long. CI < 95. Papua New Guinea . . . . . Proceratium ivimka

52

return to couplet #50

  • Species with the combination of the following characters: frontal area slightly narrower than 1/3 of HW; TL varying between 2.3 and 2.7 mm; petiole at least 1 and 1/2 broader than long (PeW ≤ 0.27 mm); propodeal sides at most denticulate; HbaL ≤ 0.24; mid basitarsi with a hair at least 2/3 of basitarsal length; hind basitarsi with a hair at least 1/2 of its length (Fig. 134). Papua New Guinea, Philippines, Sumatra, Malaysia, Sabah and Solomon Islands . . . . . Proceratium papuanum
Head of Proceratium papuanum worker
Lateral view of Proceratium papuanum worker
  • Species without the above mentioned combination of characters . . . . . 53

53

return to couplet #52

  • Species with the combination of the following characters: frontal area at most 1/4 of HW. TL 2.4 - 2.7 mm; petiole more than 1 and 1/2 broader than long (PeW 0.33 mm); HbaL ≤ 0.26; mid basitarsi with hairs shorter than 2/3 of their length; hind basitarsi with hairs shorter than 2/3 of their length (Fig. 138). Queensland (Australia) . . . . . Proceratium pumilio
Head of Proceratium pumilio worker
Lateral view of Proceratium pumilio worker
  • Species without the above mentioned combination of characters . . . . . 54

54

return to couplet #53

  • Species with the following combination of characters: SI > 73; body with many long, standing hairs; frontal area at least 1/3 of the maximum HW; propodeal sides at most subangulate (Fig. 135). Australia (Queensland) . . . . . Proceratium hirsutum
Head of Proceratium hirsutum worker
Lateral view of Proceratium hirsutum worker
  • Species without the above combination of characters . . . . . 55

55

return to couplet #54

  • Species with the combination of the following characters: frontal area slightly less than 1/4 of the maximum HW; petiole narrower than 1 and 1/2 of its length; integument smooth and shining (Fig. 132). New Caledonia . . . . . Proceratium caledonicum
Lateral view of Proceratium caledonicum worker
  • Species without the above mentioned combination of characters . . . . . 56

56

return to couplet #55

  • Species with the combination of the following characters: frontal area at least 1/3 of the maximum HW; petiole about 1 and ½ broader than its length; head, mesosoma, petiole, postpetiole and gaster smooth and shining (Fig. 131). New Caledonia . . . . . Proceratium politum
Head of Proceratium politum worker
Lateral view of Proceratium politum worker
  • Species without the above mentioned combination of characters . . . . . 57

57

return to couplet #56

  • Species with the following combination of characters: TL > 3.7 mm.; frontal area broader than 1/3 of the maximum HW; petiole less than 1 and 1/2 broader than long; mid basitarsi with hairs shorter than 1/2 of their length (Fig. 153). United States . . . . . Proceratium croceum
Head of Proceratium croceum worker
Lateral view of Proceratium croceum worker
  • Species without the above mentioned combination of characters . . . . . 58

58

return to couplet #57

  • Species with the following combination of characters: petiole less than 1 and 1/2 broader than long; frontal area 1/4 of HW; head, mesosoma, petiole and postpetiole densely granulopunctate; mid basitarsi with at least one hair 2/3 of their length; hind basitarsi with at least one hair 1/2 of their length. SI < 70. CI < 91 (Fig. 136). Thailand . . . . . Proceratium siamense
Head of Proceratium siamense worker
Lateral view of Proceratium siamense worker
  • Species without the above mentioned combination of characters . . . . . 59

59

return to couplet #58

  • Species with the following combination of characters: frontal area slightly narrower than 1/3 of the maximum HW; head densely punctate; mesosoma, petiole, postpetiole and gaster smooth and shining; SI > 70. CI > 94; propodeal sides clearly angulate or denticulate (Fig. 133). Malaysia (Pahang) . . . . . Proceratium terraealtae
Lateral view of Proceratium terraealtae worker
  • Species without the above mentioned combination of characters . . . . . 60

60

return to couplet #59

  • Species with the following combination of characters: hairs of mid basitarsi never longer than 1/2 of the basitarsal length; hind basitarsi with at least a hair slightly longer than 1/3 of their length . . . . . 61
  • Species with the combination of the following characters: mid basitarsi with at least a hair 2/3 of their length; hind basitarsi with at least a hair about 1/2 of their length . . . . . 67

61

return to couplet #60

  • Propodeal sides at most angulate. Postpetiole and gaster smooth and shining . . . . . 62
  • Propodeal sides with a small denticle, if subangulate, the postpetiole is always sculptured . . . . . 63

62

return to couplet #61

  • Standing hairs on the gaster very sparse and suberect. Mid basitarsi with hairs at most 1/3 of the basitarsal length. CI < 93. SI > 68. Australia (Queensland) . . . . . Proceratium gracile
Head of Proceratium gracile worker
Lateral view of Proceratium gracile worker
  • Standing hairs on the gaster denser, subdecumbent and decumbent. Mid basitarsi with hairs about 1/2 of the basitarsal length. CI > 94. SI < 65. Australia (New South Wales) . . . . . Proceratium robustum
Head of Proceratium robustum worker
Lateral view of Proceratium robustum worker

63

return to couplet #61

  • Species with the following combination of characters: frontal area 1/3 HW; PeW ≤ 0.29 mm; postpetiole very sparsely granulopunctate (Fig. 142). Tunisia, Cyprus, Algeria, Turkey and Albania . . . . . Proceratium numidicum
  • Species without the above mentioned combination of characters . . . . . 64

64

return to couplet #63

  • Mesosoma and postpetiole strongly granulopunctate (Figs. 129, 143) . . . . . 65
  • Mesosoma and postpetiole less strongly granulopunctate (Figs. 159, 165) . . . . . 66

65

return to couplet #64

  • Frontal area 1/4 of HW (Fig. 129). Colour dark ferruginous. Sarawak . . . . . Proceratium dayak
Head of Proceratium dayak worker
Lateral view of Proceratium dayak worker
  • Frontal area slightly narrower than 1/3 of HW (Fig. 143). Colour yellow to brown. Japan, Taiwan . . . . . Proceratium japonicum
Head of Proceratium japonicum worker
Lateral view of Proceratium japonicum worker

66

return to couplet #64

  • Frontal area about 1/4 of HW and frontal carinae gently diverging posteriorly (Fig. 165). Standing hairs on the postpetiole and gaster sparser and shorter. United States . . . . . Proceratium crassicorne
Lateral view of Proceratium crassicorne worker
  • Frontal area larger than 1/4 of HW and frontal carinae strongly diverging on the two anterior thirds (Fig. 159). Standing hairs on the postpetiole and gaster denser and longer. Southern Canada and United States . . . . . Proceratium silaceum
Head of Proceratium silaceum worker
Lateral view of Proceratium silaceum worker

67

return to couplet #60

  • Mesosoma, petiole and postpetiole minutely punctate only. Papua New Guinea, and Solomon Islands? . . . . . Proceratium austronesicum
Lateral view of Proceratium austronesicum worker


  • Mesosoma, petiole and postpetiole densely punctate and variably granulate . . . . . 68

68

return to couplet #67

  • Posterior half of the head dorsum and anterior half of the mesosoma smooth and minutely punctate. Petiole less than 1 and 1/2 broader than long. Mexico, Belize, Guatemala?, Honduras, Costa Rica, and Colombia . . . . . Proceratium mancum
Head of Proceratium mancum worker
Lateral view of Proceratium mancum worker
  • Species without the above mentioned combination of characters . . . . . 69

69

return to couplet #68

Head of Proceratium sulawense worker
Lateral view of Proceratium sulawense worker

70

return to couplet #69

Lateral view of Proceratium banjaranense worker
  • IGR ≥ 0.48. First gastral tergite less convex (Figs. 137, 149) . . . . . 71

71

return to couplet #70

  • Mesosoma, petiole and postpetiole densely granulopunctate. Sabah . . . . . Proceratium dusun
Head of Proceratium dusun worker
Lateral view of Proceratium dusun worker
  • Mesosoma, petiole and postpetiole punctate and sparsely granulate. Australia (Queensland, New South Wales) . . . . . Proceratium australe
Head of Proceratium australe worker
Lateral view of Proceratium australe worker