# Key to Pheidole majors of Borneo

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

Because the major of *P. gombakensis* sp. nov. has not been collected from Borneo, the major from Ulu Gombak, southern Malay Peninsula are used for making the keys “A” and “C.”

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## 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 forming conspicuous club; hypostoma bearing three low median processes; subpetiolar process low, with ventral margin carinate
**. . . . . 3**

- Antenna lacking conspicuous club; hypostoma lacking distinct median processes; subpetiolar process absent
**. . . . . 4**

## 3

return to couplet #2

- Head in profile distinctly impressed on vertex . . . . .
*Pheidole quinata*

- Head in profile not, or only slightly, impressed on vertex . . . . .
*Pheidole sabahna*

## 4

return to couplet #2

- Dorsum of promesonotal dome in front of the prominence on its posterior declivity bearing 10-20 standing hairs; propodeal spine at least 3.5 times as long as diameter of propodeal spiracle; body light brown to reddish brown . . . . .
*Pheidole montana*

- Dorsum of promesonotal dome in front of the prominence on posterior declivity bearing less than 10 standing hairs in
*Pheidole longipes*, or ca. 20 standing hairs in*Pheidole comata*; propodeal spine usually at most 2.5 times as long as diameter of propodeal spiracle; body reddish brown to dark brown**. . . . . 5**

## 5

return to couplet #4

- Head densely bearing standing hairs over the surface; lateral face of occipital lobe distinctly rugose; dorsum of promesonotal dome in front of the prominence on its posterior declivity bearing ca. 20 standing hairs . . . . .
*Pheidole comata*

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

## 6

return to couplet #1

- Promesonotum armed with a pair of long and pointed spines; hypostoma always bearing a pair of stout median processes
**. . . . . 7**

- Promesonotum unarmed, or each dorsolateral portion of promesonotum produced outward (e.g.,
*Pheidole aristotelis*), but never armed with long and pointed spines; hypostoma bearing 0-3 median processes**. . . . . 11**

## 7

return to couplet #6

- Gaster smooth and shining over the surface, or only anterior part of first gastral tergite near its articulation with postpetiole weakly punctured; petiolar node in profile acute at apex . . . . .
*Pheidole acantha*

- At least first gastral tergite punctured or rugoso-punctured and dull over the surface; petiolar node in profile blunt at apex
**. . . . . 8**

## 8

return to couplet #7

- Propodeal spine digitiform and blunt apically; alitrunk sparsely covered with relatively short standing hairs . . . . .
*Pheidole quadricuspis*

- Propodeal spine horn-like or elongate-triangular, pointed apically; alitrunk covered with relatively long standing hairs
**. . . . . 9**

## 9

return to couplet #8

- Propodeal spine elongate-triangular with broad base . . . . .
*Pheidole quadrensis*

- Propodeal spine horn-like with narrow base
**. . . . . 10**

## 10

return to couplet #9

- Body larger (e.g., HW 2.79-2.91 mm); subpetiolar process completely absent . . . . .
*Pheidole lokitae*

- Body smaller (e.g., HW 1.73-2.12 mm); petiole with very low subpetiolar process . . . . .
*Pheidole spinicornis*

## 11

return to couplet #6

- Legs from apex of femur to apex of tarsus 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 clypeus . . . . .
*Pheidole upeneci*

- Frontal lobe sometimes developed, but never extending beyond anterior margin of clypeus
**. . . . . 13**

## 13

return to couplet #12

- Eye consisting of 5-7 ommatidia; terminal segment of antenna more than 1.6 times as long as preceding two segments together . . . . .
*Pheidole parvicorpus*

- Eye consisting of at least 10 ommatidia; terminal segment of antenna at most 1.3 times as long as preceding two segments together
**. . . . . 14**

## 14

return to couplet #13

- Frons irregularly reticulate; hypostoma bearing a stout median process; frontal carina horizontal, extensively overhanging antennal scrobe; each dorsolateral portion of promesonotal dome produced outward . . . . .
*Pheidole aristotelis*

- Frons longitudinally rugose; hypostoma bearing 0-3 median processes; the condition of frontal carina and antennal scrobe variable; each dorsolateral portion of promesonotal dome sometimes produced outward
**. . . . . 15**

## 15

return to couplet #14

- Masticatory margin of mandible having two denticles before basal angle; ventral faces of midcoxa and hindcoxa distinctly reticulate (this condition exclusively shared with
*Pheidole aristotelis*among others)**. . . . . 16**

- Masticatory margin of mandible having at most one denticle before basal angle; ventral faces of midcoxa and hindcoxa completely smooth and shining
**. . . . . 20**

## 16

return to couplet #15

- Lateral portion of clypeus developed into a horn . . . . .
*Pheidole clypeocornis*

- Lateral portion of clypeus never developed into a horn
**. . . . . 17**

## 17

return to couplet #16

- Outer face of mandible sculptured with rugulae running from its base toward its masticatory margin . . . . .
*Pheidole rugifera*

- Outer face of mandible smooth and shining, or rugose laterally only around its base
**. . . . . 18**

## 18

return to couplet #17

- Frons (the area between frontal carinae) reticulate in its posterior part where spaces enclosed by rugulae punctured and dull . . . . .
*Pheidole tenebricosa*

- Frons longitudinally rugose or rugoso-reticulate in its posterior part where spaces enclosed by rugulae almost smooth and shining
**. . . . . 19**

## 19

return to couplet #18

- Frons in profile relatively flat . . . . .
*Pheidole hortensis*

- Frons in profile relatively convex . . . . .
*Pheidole kikutai*

## 20

return to couplet #15

- Frontal carina horizontal, extensively overhanging antennal scrobe; hypostoma always bearing one large median process
**. . . . . 21**

- Frontal carina sometimes well developed, but not overhanging antennal scrobe extensively; hypostoma bearing 0-3 median processes
**. . . . . 23**

## 21

return to couplet #20

- Clypeus having a distinct median longitudinal carina . . . . .
*Pheidole retivertex*

- Clypeus lacking a median longitudinal carina
**. . . . . 22**

## 22

return to couplet #21

- Frontal lobe well developed and suberect; frons sparsely covered with longitudinal rugulae . . . . .
*Pheidole tjibodana*

- Frontal lobe poorly developed; frons densely covered with longitudinal rugulae ...... . . . . .
*Pheidole sayapensis*

## 23

return to couplet #20

- Each dorsolateral portion of promesonotum produced as a stout horn; eye small (distance between mandibular insertion and anterior margin of eye 2.1-2.6 times as long as maximal diameter of eye); postpetiole broad (2.3-2.8 times as broad as petiolar node) . . . . .
*Pheidole angulicollis*

- Each dorsolateral portion of promesonotum sometimes produced but not forming a stout horn; eye 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 (usually less than 2.3 times as broad as petiolar node)
**. . . . . 24**

## 24

return to couplet #23

- Petiolar node in profile highly prominent; hypostoma always bearing a pair of median processes; occasionally the processes poorly developed in
*P. elisae*Emery); mesopleuron divided by a transverse impression into two parts, of which lower part is always margined dorsally; alitrunk, or at least its large part, smooth and shining**. . . . . 25**

- Petiolar node in profile usually poorly prominent (with exceptions as seen in
*Pheidole bugi*, in which, however, hypostoma bears three similar-sized median processes); when mesopleuron divided by a transverse impression into two parts, lower part is usually not margined dorsally (with exceptions as seen in*Pheidole poringensis*, in which alitrunk is reticulate)**. . . . . 27**

## 25

return to couplet #24

- Dorsum of head completely covered with longitudinal rugulae . . . . .
*Pheidole sauberi*

- Dorsum of occipital lobe smooth and shining
**. . . . . 26**

## 26

return to couplet #25

- Eight ommatidia present on longest axis of eye . . . . .
*Pheidole elisae*

- Four to five ommatidia present on longest axis of eye . . . . .
*Pheidole sarawakana*

## 27

return to couplet #24

- Alitrunk completely lacking standing hairs . . . . .
*Pheidole huberi*

- Alitrunk bearing standing hairs
**. . . . . 28**

## 28

return to couplet #27

- Propodeal spine extremely long, extending over petiolar node . . . . .
*Pheidole modiglianii*

- Propodeal spine at most slightly passing posterior end of propodeal lobe
**. . . . . 29**

## 29

return to couplet #28

- Dorsum of occipital lobe smooth and shining (or only weakly and sparsely rugose in
*Pheidole manukana*where postpetiole 2.4-2.6 times as broad as petiolar node)**. . . . . 30**

- Dorsum of head including that of occipital lobe completely sculptured (or rugulae on occipital lobe weak in
*Pheidole orophila*sp. nov. where, however, postpetiole 1.6-1.7 times as broad as petiolar node)**. . . . . 36**

## 30

return to couplet #29

- Hypostoma always lacking median processes; petiole less than 1.2 times as long as postpetiole
**. . . . . 31**

- Hypostoma bearing 1-3 median processes; (in part of
*Pheidole lucioccipitalis*hypostoma lacks all the median processes where petiole is more than 1.5 times as long as postpetiole)**. . . . . 33**

## 31

return to couplet #30

- Distance between mandibular insertion and anterior margin of eye ca. 2.3-2.4 times as long as maximal diameter of eye . . . . .
*Pheidole havilandi*

- Distance between mandibular insertion and anterior margin of eye 1.4-1.6 times as long as maximal diameter of eye
**. . . . . 32**

## 32

return to couplet #31

- Postpetiole 2.4-2.6 times as broad as petiolar node; frontal carina conspicuous . . . . .
*Pheidole manukana*

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

## 33

return to couplet #30

- Posterior declivity of promesonotal dome having a distinct prominence . . . . .
*Pheidole plinii*

- Posterior declivity of promesonotal dome lacking a distinct prominence
**. . . . . 34**

## 34

return to couplet #33

- Hypostoma bearing an indistinct median process, or lacking median process; clypeus having a median longitudinal carina . . . . .
*Pheidole lucioccipitalis*

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

## 35

return to couplet #34

- Promesonotum narrower dorsally than ventrally . . . . .
*Pheidole deltea*

- Promesonotum broader dorsally than ventrally . . . . .
*Pheidole merimbun*

## 36

return to couplet #29

- Posterior declivity of promesonotal dome lacking a distinct prominence; if the declivity has an inconspicuous prominence (as seen in
*Pheidole poringensis*), hypostoma bearing 2-3 distinct median processes**. . . . . 37**

- Posterior declivity of promesonotal dome having a distinct prominence; if the declivity has just an inconspicuous prominence (as seen in
*Pheidole submonticola*), hypostoma completely lacking median processes**. . . . . 43**

## 37

return to couplet #36

- Frontal lobe relatively large and erect . . . . .
*Pheidole tawauensis*

- Frontal lobe relatively small
**. . . . . 38**

## 38

return to couplet #37

- Posterior margin of head weakly concave in full-face view; dorsum of promesonotum smooth and shining (with several rugulae) . . . . .
*Pheidole planidorsum*

- Posterior margin of head strongly concave in full-face view; dorsum of promesonotum sculptured or smooth
**. . . . . 39**

## 39

return to couplet #38

- Hypostoma bearing three median processes
**. . . . . 40**

- Hypostoma bearing a pair of stout median processes; if hypostoma bears three median processes, then the medianmost one is much reduced (as seen in
*Pheidole rabo*and*Pheidole poringensis*)**. . . . . 41**

## 40

return to couplet #39

- Petiolar node relatively high . . . . .
*Pheidole parva*

- Petiolar node relatively low . . . . .
*Pheidole butteli*

## 41

return to couplet #39

- Petiole almost twice as long as postpetiole (excluding helcium); lateral face of promesonotum almost smooth and shining . . . . .
*Pheidole gombakensis*

- Petiole at most 1.7 times as long as postpetiole (excluding helcium); lateral face of promesonotum sculptured
**. . . . . 42**

## 42

return to couplet #41

- Petiole ca. 1.7 times as long as postpetiole (excluding heIcium); outer face of mandible sparsely covered with very short appressed hairs . . . . .
*Pheidole rabo*

- Petiole 1.3-1.4 times as long as postpetiole (excluding heIcium); outer face of mandible sparsely covered with relatively long decumbent hairs . . . . .
*Pheidole poringensis*

## 43

return to couplet #36

- Hypostoma bearing three low median processes, of which each lateral one is partly combined with the process just mesal to mandibular insertion . . . . .
*Pheidole annexa*

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

## 44

return to couplet #43

- Hypostoma bearing a pair of stout median processes ; petiole almost as long as postpetiole which is relatively massive . . . . .
*Pheidole ghigii*

- If hypostoma bears a pair of small or indistinct median processes, then petiole is at least 1.2 times as long as postpetiole
**. . . . . 45**

## 45

return to couplet #44

- Propodeal spine elongate-triangular, with broad base; outer face of mandible bearing short or very short, appressed hairs
**. . . . . 46**

- Propodeal spine horn-like, with narrow base; outer face of mandible usually bearing relatively long, appressed or decumbent hairs
**. . . . . 47**

## 46

return to couplet #45

- Antennal scrobe margined below with a conspicuous carina anteriorly; mesopleuron without a distinct transverse impression . . . . .
*Pheidole cariniceps*

- Antennal scrobe present only around antennal insertion, and never margined below with a conspicuous carina; mesopleuron divided by a transverse impression into two parts, of which lower part margined dorsally . . . . .
*Pheidole submonticola*

## 47

return to couplet #45

- Posteriormost part of dorsum of occipital lobe almost transversely rugose . . . . .
*Pheidole plagiaria*

- Dorsum of occipital lobe sculptured, but never transversely rugose
**. . . . . 48**

## 48

return to couplet #46

- Frontal carina weak; lateral face of occipital lobe smooth or very weakly rugoso-punctured . . . . .
*Pheidole jacobsoni*

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

## 49

return to couplet #48

- Posterior margin of head strongly concave in full-face view . . . . .
*Pheidole aglae*

- Posterior margin of head weakly concave 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 . . . . .
*Pheidole fervens*

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