Key to Pheidole majors and minors of Borneo

This worker key is based on: [[Media:Eguchi 2001a.pdf| Eguchi, K. 2001a. A revision of the Bornean species of the ant genus Pheidole (Insecta: Hymenoptera: Formicidae: Myrmicinae). Tropics Monograph Series. 2:1-154. PDF]]

This key is designed to be used with samples that include both the major and minor workers from the same colony.

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 * Pheidole
 * Key to Pheidole majors of Borneo
 * Key to Pheidole minors of Borneo

1

 * Antenna with 3-segmented club . . . . . 6


 * Antenna with 5-segmented club, or without conspicuous club . . . . . 2

2
return to couplet #1
 * Apical five antennal segments distinctly elongate and forming conspicuous club in both the subcastes; posterior part of head never forming elongate neck in the minor; hypostoma of the major bearing three low median processes; low subpetiolar process present in the major . . . . . 3


 * Antenna lacking conspicuous club in both the subcastes; posterior part of head of the minor forming elongate neck; hypostoma of the major lacking distinct median processes; subpetiolar process absent in both the subcastes . . . . . 4

3
return to couplet #2
 * Head of the major in profile distinctly impressed on vertex; promesonotal dome of the minor relatively high; metanotal groove of the minor in profile indistinct . . . . . Pheidole quinata


 * Head of the major in profile not, or slightly, impressed on vertex; promesonotal dome of the minor relatively low; metanotal groove of the minor in profile distinct . . . . . Pheidole sabahna

4
return to couplet #2
 * Propodeal spine more than 4 times as long as diameter of propodeal spiracle in the minor; body light brown to brown in both the subcastes . . . . . Pheidole montana


 * Propodeal spine 2-2.5 times as long as diameter of propodeal spiracle in the minor; body reddish brown to dark brown in both the subcastes . . . . . 5

5
return to couplet #4
 * Head of the major densely bearing standing hairs over the surface; lateral face of occipital lobe distinctly rugose in the major; in profile dorsum of promesonotal dome in front of the prominence on its posterior declivity bearing ca. 20 standing hairs in the major . . . . . Pheidole comata


 * Head of the major with sparse standing hairs only on frons and vertex; lateral face of occipital lobe weakly and finely rugose, or almost smooth and shining in the major; in profile dorsum of promesonotal dome in front of the prominence on its posterior declivity bearing at most 10 standing hairs in the major . . . . . Pheidole longipes

6
return to couplet #1
 * Promesonotum armed with a pair of long and pointed spines in both the subcastes; hypostoma of the major always bearing a pair of stout median processes . . . . . 7


 * Promesonotum unarmed in both the subcastes, or armed with a pair of processes, but the processes never developing into long and pointed spines (the processes of the minor of P. aristotelis well developed, but truncate or blunt apically in the minor); hypostoma of the major bearing 0-3 median processes . . . . . 11

7
return to couplet #6
 * Propodeal spine digitiform and blunt apically in the major, and elongate-triangular, ca. 1.5 times as long as diameter of propodeal spiracle in the minor; head of the minor smooth and shining . . . . . Pheidole quadricuspis


 * Propodeal spine usually pointed apically in the major, and horn-like, more than 4 times as long as diameter of propodeal spiracle in the minor; head of the minor usually sculptured at least partly (in P. acantha head of the minor sometimes almost completely smooth and shining) . . . . . 8

8
return to couplet #7
 * Gaster of the major smooth and shining over the surface, or only anterior part of first gastral tergite around its articulation with postpetiole weakly punctured; petiolar node of both the subcastes in profile acute at apex; dorsum of alitrunk in profile bearing only less than 10 standing hairs in the minor  . . . . . Pheidole acantha


 * At least first gastral tergite of the major punctured and dull; petiolar node of both the subcastes in profile blunt at apex; dorsum of alitrunk in profile usually bearing more than 20 standing hairs in the minor . . . . . 9

9
return to couplet #8
 * Head punctured, or largely smooth and shining but partly punctured in the minor . . . . . Pheidole spinicornis


 * Head strongly reticulate in the minor . . . . . 10

10
return to couplet #9
 * Propodeal spine elongate-triangular, with broad base in the major, and horn-like, usually directed upward in the minor; petiole of the major with low subpetiolar process; body smaller (e.g., HW: 1.90-2.28 mm in the major, 0.67-0.78 mm in the minor) . . . . . Pheidole quadrensis


 * Propodeal spine horn-like, with narrow base in the major, and horn-like, directed posterodorsally in the minor; petiole of the major without any subpetiolar process; body larger (e.g., HW: 2.79-2.91 mm in the major, 1.04-1.11 mm in the minor) . . . . . Pheidole lokitae

11
return to couplet #6
 * Legs from apex of femur to apex of tersus ivory-white contrasted with remainder of femur which is dark brown . . . . . Pheidole fantasia


 * Legs almost unicolored . . . . . 12

12
return to couplet #11
 * Frontal lobe extremely developed, extending beyond anterior margin of c1ypeus in the major . . . . . Pheidole upeneci


 * Frontal lobe sometimes developed, but never extending beyond anterior margin of c1ypeus in the major . . . . . 13

13
return to couplet #12
 * Eye consisting of 5-7 ommatidia in both the subcastes; terminal antennal segment more than 1.6 times as long as preceding two segments together in both the subcastes . . . . . Pheidole parvicorpus


 * Eye consisting of at least ten, usually more than 15, ommatidia in both the subcastes; terminal antennal segment at most 1.3 times as long as preceding two segments together in both the subcastes . . . . . 14

14
return to couplet #13
 * Frons irregularly reticulate; hypostoma bearing a stout median process in the major rarely the process is poorly developed); frontal carina horizontal, extensively overhanging antennal scrobe in the major; each dorsolateral portion of promesonotal dome angulate outward in the major, and armed with a pair of blunt spines in the minor . . . . . Pheidole aristotelis


 * Frons of the major longitudinally rugose; hypostoma bearing 0-3 median processes in the minor condition of frontal carina and antennal scrobe variable in the major; each dorsolateral portion of promesonotal dome sometimes produced outward in the major, and sometimes armed with a pair of low tubercles in the minor (but the tubercles never developed into distinct spines as seen in P. aristotelis) . . . . . 15

15
return to couplet #14
 * Masticatory margin of mandible of the major having two denticles in front of basal angle; ventral faces of midcoxa and hindcoxa of the major distinctly reticulate (this condition exclusively shared with P. aristotelis among others) . . . . . 16


 * Masticatory margin of mandible of the major having at most a denticle in front of basal angle; ventral faces of midcoxa and hindcoxa of the major completely smooth and shining . . . . . 20

16
return to couplet #15
 * Head above subocular level and alitrunk punctured and dull in the minor . . . . . 17


 * Head and alitrunk smooth and shining in the minor . . . . . 18

17
return to couplet #16
 * Outer face of mandible of the major sculptured with rugulae running from its base toward its masticatory margin  . . . . . Pheidole rugifera


 * Outer face of mandible of the major rugose laterally only around at most its base . . . . . Pheidole tenebricosa

18
return to couplet #16
 * Occipital carina of the minor complete . . . . . Pheidole kikutai


 * Occipital carina of the minor absent dorsally on head . . . . . 19

19
return to couplet #18
 * Lateral portion of clypeus produced into a horn in the major . . . . . Pheidole clypeocornis


 * Lateral portion of clypeus never produced into a horn in the major . . . . . Pheidole hortensis

20
return to couplet #15
 * In the major frontal carina horizontal, overhanging antennal scrobe; hypostoma of the major always bearing a large median process; head of the minor always rugoso-reticulate or punctured . . . . . 21


 * In the major frontal carina sometimes well developed, but not overhanging antennal scrobe extensively; hypostoma of the major bearing 0-3 median processes; head of the minor smooth and shining, or sculptured . . . . . 23

21
return to couplet #20
 * Head weakly rugoso-reticulate and lateral face of alitrunk weakly punctured in the minor; c1ypeus of the major having a distinct median longitudinal carina . . . . . Pheidole retivertex


 * Head and alitrunk distinctly punctured or reticulate in the minor; c1ypeus of the major lacking a median longitudinal carina . . . . . 22

22
return to couplet #21
 * Head and alitrunk of the minor punctured; frontal lobe of the major well developed and suberect  . . . . . Pheidole tjibodana


 * Head and alitrunk of the minor reticulate; frontal lobe of the major poorly developed . . . . . Pheidole sayapensis

23
return to couplet #20
 * Each dorsolateral portion of promesonotum produced as a blunt horn directed dorsolaterally in the major; eye of the major small (distance between mandibular insertion and anterior margin of eye 2.1-2.6 times as long as maximal diameter of eye; postpetiole broad in the major (2.3-2.8 times as broad as petiolar node) . . . . . Pheidole angulicollis


 * Each dorsolateral portion of promesonotum sometimes produced laterally but not forming a blunt horn directed dorsolaterally in the major; eye of the major variable in size (distance between mandibular insertion and anterior margin of eye usually less than twice as long as maximal diameter of eye); postpetiole variable in width in the major (usually less than 2.3 times as broad as petiolar node) . . . . . 24

24
return to couplet #23
 * Petiolar node in profile highly elevated in both the subcastes; hypostoma of the major always bearing a pair of median processes (occasionally the processes poorly developed in P. elisae Emery); mesopleuron of both the subcastes divided into two parts, of which lower part is usually margined dorsally; head and promesonotum always smooth and shining in the minor . . . . . 25


 * Petiolar node in profile usually relatively low in both the subcastes (with exceptions as seen in the minor of P. gombakensis sp. nov.; hypostoma bearing 0-3 median processes (the major of P. gombakensis having a pair of median processes on hypostoma where the processes, however, extremely developed; if mesopleuron is divided into two parts, the lower part is usually not margined dorsally; head and promesonotum smooth and shining, or sculptured in the minor . . . . . 27

25
return to couplet #24
 * Dorsum of head entirely longitudinally rugose up to posterior extremity of occipital lobe in the major  . . . . . Pheidole sauberi


 * Dorsum of occipital lobe smooth and shining in the major . . . . . 26

26
return to couplet #25
 * Longest axis of eye having 8 ommatidia in the major, and 6-7 ommatidia in the minor . . . . . Pheidole elisae


 * Longest axis of eye having 4-5 ommatidia in the major, and 4 ommatidia in the minor . . . . . Pheidole sarawakana

27
return to couplet #24
 * Alitrunk of both the subcastes completely lacking standing hairs . . . . . Pheidole huberi


 * Alitrunk of both the subcastes bearing standing hairs . . . . . 28

28
return to couplet #27
 * Propodeal spine extremely long, extending over petiolar node in both the subcastes  . . . . . Pheidole modiglianii


 * Propodeal spine extending at most slightly beyond posterior end of propodeal lobe in both the subcastes . . . . . 29

29
return to couplet #28
 * Dorsum of occipital lobe of the major smooth and shining (or only weakly and very sparsely rugose in P. manukana where postpetiole of the major 2.4-2.6 times as broad as petiolar node) . . . . . 30


 * Dorsum of head of the major sculptured (or rugulae on occipital lobe weak in P. jacobsoni where, however, postpetiole of the major 1.6-1.7 times as broad as petiolar node) . . . . . 36

30
return to couplet #29
 * Hypostoma of the major always lacking median processes; petiole of both the subcastes less than 1.2 times as long as postpetiole . . . . . 31


 * Hypostoma of the major bearing 1-3 median processes (in some specimens of P. lucioccipitalis median processes sometimes almost absent where petiole is more than 1.5 times as long as post petiole in both the subcastes) . . . . . 33

31
return to couplet #30
 * Distance between mandibular insertion and anterior margin of eye 2.3-2.4 times as long as maximal diameter of eye in the major, and ca. 1.5 times in the minor . . . . . Pheidole havilandi


 * Distance between mandibular insertion and anterior margin of eye 1.4-1.5 times as long as maximal diameter of eye in the major, and 1.0-1.1 times in the minor . . . . . 32

32
return to couplet #31
 * Postpetiole 2.4-2.6 times as broad as petiolar node in the major; frontal carina of the major conspicuous . . . . . Pheidole manukana


 * Postpetiole 1.8-1.9 times as broad as petiolar node in the major; frontal carina of the major inconspicuous . . . . . Pheidole megacephala

33
return to couplet #30
 * Posterior declivity of promesonotal dome having a distinct prominence in both the subcastes; promesonotal dome of the minor having a pair of low tubercles . . . . . Pheidole plinii


 * Posterior declivity of promesonotal dome lacking a distinct prominence in both the subcastes; promesonotal dome of the minor unarmed . . . . . 34

34
return to couplet #33
 * Hypostoma of the major bearing an indistinct median process, or lacking median processes; clypeus of the major having a median longitudinal carina  . . . . . Pheidole lucioccipitalis


 * Hypostoma of the major bearing 2-3 median processes; clypeus of the major lacking a median longitudinal carina . . . . . 35

35
return to couplet #34
 * Promesonotum of the major narrower dorsally than ventrally; propodeal spine of the minor 3.5-4 times as long as diameter of propodeal spiracle  . . . . . Pheidole deltea


 * Promesonotum of the major broader dorsally than ventrally; propodeal spine of the minor twice as long as diameter of propodeal spiracle  . . . . . Pheidole merimbun

36
return to couplet #29
 * Posterior declivity of promesonotal dome of the major lacking a distinct prominence; if the declivity has an inconspicuous prominence (e.g., P. poringensis), hypostoma of the major bears 2-3 distinct median processes . . . . . 37


 * Posterior declivity of promesonotal dome of the major having a distinct prominence; if the declivity has just a small prominence as seen in P. submonticola, hypostoma of the major completely lacks median processes . . . . . 43

37
return to couplet #36
 * Promesonotum of the minor smooth and shining . . . . . 38


 * Promesonotum of the minor sculptured . . . . . 41

38
return to couplet #37
 * Promesonotal dome of the minor in profile very low and almost flat dorsally; in full-face view posterior margin of head of the major weakly concave . . . . . Pheidole planidorsum


 * Promesonotal dome of the minor in profile relatively convex dorsally; in full-face view posterior margin of head of the major usually distinctly concave . . . . . 39

39
return to couplet #38
 * Hypostoma of the major with a pair of very large median processes; dorsum of head of the minor rugoso-reticulate . . . . . Pheidole gombakensis


 * Hypostoma of the major with 2-3 median processes; if two processes are present, they are much smaller than those of P. gombakensis; head of the minor largely smooth and shining . . . . . 40

40
return to couplet #39
 * Frontal lobe of the major relatively large and erect . . . . . Pheidole tawauensis


 * Frontal lobe of the major relatively small . . . . . Pheidole butteli

41
return to couplet #37
 * Outer face of mandible of the major bearing long decumbent hairs; head of the minor reticulate . . . . . Pheidole poringensis


 * Outer face of mandible of the major sparsely bearing short appressed hairs; head of the minor punctured . . . . . 42

42
return to couplet #41
 * Distance between mandibular insertion and anterior margin of eye twice as long as maximal diameter of eye in the major; hypostoma of the major bearing three median processes, of which medianmost one is poorly developed . . . . . Pheidole rabo


 * Distance between mandibular insertion and anterior margin of eye ca. 1.4 times as long as maximal diameter of eye in the major; hypostoma of the major bearing three similar-sized median processes . . . . . Pheidole parva

43
return to couplet #36
 * Hypostoma of the major bearing three low median processes, of which each lateral one is partly connected to the process just mesal to mandibular insertion . . . . . Pheidole annexa


 * If hypostoma of the major bears 2-3 median processes, each lateral one is never connected to the process just mesal to mandibular insertion . . . . . 44

44
return to couplet #43
 * Hypostoma of the major bearing a pair of stout median processes; petiole of the major almost as long as postpetiole; promesonotum with a pair of low tubercles in the minor. . . . . Pheidole ghigii


 * If hypostoma of the major bears a pair of small or indistinct median processes, petiole of the major is at least 1.2 times as long as postpetiole; promesonotum without a pair of low tubercles in the minor . . . . . 45

45
return to couplet #44
 * Propodeal spine of the major elongate-triangular, with broad base . . . . . 46


 * Propodeal spine of the major horn-like, with narrow base . . . . . 47

46
return to couplet #45
 * Antennal scrobe margined below with a conspicuous carina in the major anteriorly; mesopleuron of the major without a distinct transverse impression; posterior declivity of promesonotal dome of the minor with a low prominence . . . . . Pheidole cariniceps


 * Antennal scrobe present only around antennal insertion, and never margined below with a conspicuous carina in the major; mesopleuron of the major divided by a transverse impression into two parts, of which the lower part is margined dorsally; posterior declivity of promesonotal dome of the minor without any prominence . . . . . Pheidole submonticola

47
return to couplet #45
 * Posteriormost part of dorsum of occipital lobe of the major almost transversely rugose in the major . . . . . Pheidole plagiaria


 * Posteriormost part of dorsum of occipital lobe reticulate, rugoso-reticulate or longitudinally rugose, but never transversely rugose in the major . . . . . 48

48
return to couplet #47
 * Frontal carina of the major slight; lateral face of occipital lobe of the major smooth or very weakly rugoso-punctured . . . . . Pheidole jacobsoni


 * Frontal carina of the major distinct; lateral face of occipital lobe of the major rugoso-reticulate . . . . . 49

49
return to couplet #48
 * Posterior margin of head of the major strongly concave; occipital carina of the minor forming a flange, which is narrowed at its base in full-face view . . . . . Pheidole aglae


 * Posterior margin of head of the major weakly concave; occipital carina of the minor well developed, but never narrowed at its base in full-face view . . . . . 50

50
return to couplet #49
 * Distance between mandibular insertion and anterior margin of eye 1.3-1.4 times as long as maximal diameter of eye in the major . . . . . Pheidole fervens


 * Distance between mandibular insertion and anterior margin of eye 1.7-2.0 times as long as maximal diameter of eye in the major . . . . . Pheidole inornata