Key to Pheidole species groups of Madagascar

This key to minor and major workers is based on: [[Media:Salata, S., Fisher, B.L. 2020. Pheidole of Madagascar (10.3897@zookeys.905.39592).pdf|Salata, S. and B.L. Fisher. 2020a. Pheidole Westwood, 1839 (Hymenoptera, Formicidae) of Madagascar – an introduction and a taxonomic revision of eleven species groups. ZooKeys. 905:1–235.]]

Note: This key is preliminary and ongoing revisions of all species species groups may lead to further changes. Additionally, because of high infraspecific variability of minor workers we strongly encourage the use of nest samples consisting of both major and minor workers with this key.

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 * Pheidole species group of Madagascar
 * Madagascar
 * Pheidole

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 * Social parasite of Pheidole sp. Major workers. Absent. Minor workers. Yellow, with smooth body sculpture, promesonotal and metanotal grooves absent, promesonotum evenly arched and big eyes (Fig. 2A)........Pheidole lucida  species group


 * Nonparasitic species. Both major and minor workers present. If body colouration of minor workers is yellow and body sculpture smooth them eyes never big (Fig. 2B, C) . . . . . 2

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return to couplet #1
 * Minor & major workers. Postpetiole in profile with conspicuous ventral convexity (sometimes subtriangular in major workers) (Fig. 3A, B). Minor workers. Head smooth, scape relatively short, surpassing the posterior head margin by two-fifths of its length, promesonotum in lateral view convex (Fig. 3A). Major workers. Head oval to cordate; occipital lobes shiny and smooth or with indistinct rugulae; frons with sparse and thick longitudinal rugulae and smooth to finely rugulose interspaces; inner hypostomal teeth indistinct or absent (Figs 3B, 4D) . . . . . Pheidole megacephala species group


 * Minor & major workers. Postpetiole in profile without conspicuous convexity, ventral process indistinct or, if present, acute and present only in major workers (Fig. 2A–C). Minor workers. Head at least partially foveolate or rugulose. If head entirely smooth then scape short and not surpassing the posterior head margin and promesonotum not evenly convex or scape long, surpassing the posterior head margin by at least one-third of its length and promesonotum of different shape (Fig. 2A–C). Major workers. Head shape different; if head oval or cordate then at least one of the following characters present: occipital lobes never smooth, inner hypostomal teeth well developed, antennal scrobes present, frons with sculpture other than sparse thick longitudinal rugae (Figs 3E, F, 4C, E, F) . . . . . 3

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return to couplet #2
 * Minor & major workers. Antennal sockets deep; frontal lobes distinct and lobe-like (Fig. 4A, B). Major workers. Outer hypostomal teeth absent (Fig. 4C) . . . . . Pheidole diakritos species group
 * Minor & major workers. Antennal sockets shallow; frontal lobes absent or indistinct (Fig. 3D–F). Major workers. Outer hypostomal teeth present (Fig. 4D–F) . . . . . 4

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return to couplet #3
 * Major & minor workers. Relatively large species, propodeal spines moderately to very long, thin and acute. Major workers. Inner and outer hypostomal teeth closely spaced and often connected by concavity (Fig. 4E). Minor workers. At least genae and frons with smooth notches (except P. maizina) (Fig. 5C, D, G, H) . . . . . 5


 * Major & minor workers. Smaller species, propodeal spines short to moderately long, with wide or narrow base (Figs 7H, J, 9A–F, 10A–F). Major workers. Inner and outer teeth not closely spaced and if closely spaced, then propodeal spines shorter. Minor workers. Head foveolate, if genae and frons with smooth notches then propodeal spines short (Fig. 9A–F) . . . . . 6

5
return to couplet #4
 * Major workers. Head, in full-face view, trapezoid, widening posteriorly; head sculpture fine, occipital lobes smooth or with indistinct microsculpture; promesonotum short, low, and evenly convex (Fig. 5A, B). Minor workers. Scape, when arranged along the anteroposterior axis of the head, surpassing posterior head margin by one third or more than half of its length; promesonotum low, long, and slightly convex; petiole with long and thin peduncle (Fig. 5C, D) . . . . . Pheidole longispinosa species group
 * Major workers. Head, in full-face view, rectangular; head sculpture strong rugoreticulate, sometimes weakens posteriorly; promesonotum short, angular, and relatively low to high (Fig. 5E, F). Minor workers. Scape, when arranged along the anteroposterior axis of the head, surpassing posterior head margin by one- to two-fifths of its length; promesonotum high, short and convex; petiole with shorter and thicker peduncle (Fig. 5G, H) . . . . . Pheidole ensifera species group

6


return to couplet #4
 * Major workers. Head in full-face view rectangular and longer than wide; in lateral view sub-oval to sub-rectangular; occipital lobes always with arcuate and/or transverse rugae; genae at least with a smooth notch (Fig. 6A, B). Minor workers. Head foveolate with at least smooth notches on genae; scape short, reaching the posterior margin of head or surpassing it by one- to two-fifths of its length; promesonotum low, convex, short; propodeal spines small and triangular; mesosoma predominately foveolate but always with smooth notches (Fig. 6E) . . . . . Pheidole makaensis species group
 * Major workers. Head in full-face view not elongated; if elongated then occipital lobes lacking arcuate or transverse rugae (Figs 6C, D, 7A–D). Minor workers. Head smooth or entirely foveolate; if head foveolate with smooth notches on genae then at least one of the following characters present: scape longer, surpassing the posterior margin of head by at least one-third of its length, promesonotum flat and long, posterior mesonotum steep, propodeal spines minute or relatively long, mesosoma predominately smooth (Fig. 8G–I) . . . . . 7

7
return to couplet #6
 * Major workers. Head, in full-face view, elongate without arcuate or transverse rugae on occipital lobes or head oval; frons and lateral sides of head with thick longitudinal rugae; occipital lobes with irregular rugulae and sculpture weakening posteriorly; promesonotum high and arched; propodeal spines short with wide base (Fig. 6C, D, G). Minor workers. Head never foveolate, at least frons, genae, and malar area smooth and shiny smooth, sometimes lateral sides of frons with short, indistinct, longitudinal rugulae; scape short, when laid back, reaching posterior head margin or surpassing the posterior head margin by one-fifth of its length; mesosoma almost entirely smooth; body yellow (Fig. 6F) . . . . . Pheidole lutea species group


 * Major workers. Head not oval or elongate, if oval at least one of the following characters present: frons or lateral sides of head with thick irregular rugae, occipital lobes smooth, promesonotum low, propodeal spines relatively long (Fig. 7A–D). Minor workers. Head at least partly foveolate, if foveolae absent then at least one of the following characters present: scape longer, when laid back, surpassing the posterior head margin by at least two-fifths of its length, mesosoma at least partially foveolate, promesonotal groove present and deep, body not yellow (Fig. 8A, B, D–F) . . . . . 8

8
return to couplet #7
 * Major workers. Head, in full-face view, sub-oval to cordate; frons and lateral sides of head predominately with irregular, thick rugae, if frons with longitudinal rugae then antennal scrobes present and well delimited or head in full face view square and in lateral view oval to sub-oval, with thick and sparse longitudinal rugae present on frons and lateral sides of head, promesonotum short, steep and high without promesonotal groove (Fig. 7A–F). Minor workers. Promesonotal groove absent or indistinct. Head and mesosoma predominately foveolate; promesonotum, in lateral view, low, long and convex with indistinct to moderately long propodeal spines (Fig. 8C), if posterior mesonotum steep then propodeal spines long (Fig. 8G); if head and mesosoma predominately smooth, promesonotum short and arched and propodeal spines minute to small (Fig. 8D) . . . . . 9


 * Major workers. Head, in full-face view square to sub-rectangular, sometimes with lateral sides slightly convex; frons and lateral sides of had predominately with longitudinal rugae, promesonotum never steep or high, predominately low and arched (Fig. 7G–L). Minor workers. Promesonotal groove present and distinct (Fig. 8A, B, E, F), if absent or indistinct then head and mesosoma predominately foveolate; promesonotum, in lateral view, low, short to long with posterior mesonotum steep and propodeal spines minute to small (Fig. 8H, I) . . . . . 10

9
return to couplet #8
 * Major workers. Head, in full-face view, sub-oval to cordate; frons with longitudinal rugae and antennal scrobes present and well delimited (Fig. 7A, B). Minor workers. Promesonotal groove absent; head and mesosoma predominately foveolate; promesonotum, in lateral view, box-like or convex with posterior mesonotum steep; propodeal spines short to long (Fig. 8G, J) . . . . . Pheidole ferruginea species group


 * Major workers. Head, in full-face view, sub-oval; frons and lateral sides of had predominately with irregular, thick rugae; antennal scrobes absent or poorly delimited or head in full face view square and in lateral view oval to sub-oval, with thick and sparse longitudinal rugae present on frons and lateral sides of head (Fig. 7C–F). Minor workers. Promesonotal groove absent or indistinct. Head and mesosoma predominately foveolate; promesonotum, in lateral view, low, long and convex with indistinct to short propodeal spines or head and mesosoma predominately smooth, promesonotum short and arched and propodeal spines minute to small (Fig. 8C, D) . . . . . Pheidole sikorae species group

10


return to couplet #8
 * Major workers. Head predominately with fine, sparse longitudinal rugae, sometimes fading posteriorly or head in lateral view oval to sub-oval with thick rugae, distinctly irregular on lateral sides of head with smooth to indistinctly foveolate interspaces; antennal scrobes absent or indistinct; promesonotum low; promesonotal groove present deep or indistinct (Fig. 7G–J). Minor workers. Head elongate, the posterior region of the head elongated into short to long neck, if neck absent then promesonotum, in lateral view, relatively long to long, low and convex and promesonotal groove present (Fig. 8A, E, F, K, L) . . . . . Pheidole bessonii species group


 * Major workers. Head predominately with fine, sparse longitudinal rugae limited to frons, occipital lobes with irregular rugulae and promesonotal groove absent; if occipital lobes with fine longitudinal rugae then antennal scrobes present and distinct, promesonotum low and short with deep promesonotal groove (Fig. 7K, L). Minor workers. Head not elongated; promesonotal groove absent, if present then promesonotum, in lateral view, short, relatively high and with steep posterior mesonotum (Fig. 8B, H, I) . . . . . 11

11
return to couplet #10
 * Major workers. Promesonotal process well developed; promesonotum low and short; antennal scrobes distinct (Fig. 7K, L). Minor workers. Head and mesosoma predominately smooth and shiny; promesonotal groove present (Fig. 8B) . . . . . Pheidole fervens species group


 * Major workers. Promesonotal process absent or weakly developed; promesonotum moderately high to high; antennal scrobes absent or present but not delimited by carinulae (Figs 10A–F, 11A–D). Minor workers. Head and mesosoma predominately foveolae, sometimes with smooth notches; promesonotal groove absent (Fig. 8H, I) . . . . . 12

12
return to couplet #11
 * Major & minor workers. Mesonotal spines present (sometimes major workers with teeth-like spines), propodeal spines long (Figs 9A, 10A) . . . . . Pheidole annemariae species group


 * Major & minor workers. Mesonotal spines absent (sometimes major workers with bulge-like process), propodeal spines short to moderately long (Figs 9B–F, 10B–F) . . . . . 13

13
return to couplet #12
 * Major workers. Small body size (WL < 0.9 mm); head, in lateral view, sub-rectangular; ventral and dorsal faces relatively flat; antennal scrobes, when present, indistinctly to distinctly delimited (Figs 10B,C, 11A, B). Minor workers. Small body size (WL < 0.6mm); body yellow and foveolate with no additional sculpture (except P. lamperos and P. zavamanira); genae always smooth; propodeal spines minute to small. Minor workers are indistinguishable from those of the nemoralis species group (Fig. 9B, C) . . . . . Pheidole masoala species group


 * Major workers. Body bigger (WL > 1.0 mm), if WL < 0.9 then head in lateral view, sub-rectangular to sub-oval, with ventral and dorsal faces convex and antennal scrobes not delimited (Figs 10D–F, 11C–E). Minor workers. Body bigger (WL > 0.65mm), if WL < 0.6 then body yellow or dark brown; head and mesosoma entirely foveolate or with distinct smooth notches; sometimes head and/or mesosoma with additional rugae. Note: Minor workers of the masoala species group are indistinguishable from those of the nemoralis species group (Fig. 9D–F) . . . . . 14

14
return to couplet #13
 * Major workers. Head in full face view rectangular, slightly widening posteriorly, in lateral view sub-rectangular with ventral and dorsal faces finely convex (Figs 10F, 11E). Minor workers. Head foveolate, with thick, sparse, and longitudinal rugae on frons and sparse, irregular to arcuate, thick rugae on vertex; mesosoma foveolate or foveolate with additional thick and irregular rugae; body yellow to brown (Fig. 9F) . . . . . Pheidole curvistriata species group


 * Major workers. Head in full face view square to sub-rectangular, never widening posteriorly, in lateral view sub-oval or sob-rectangular with ventral and dorsal faces finely convex (Figs 10D, E, 11C, D). Minor workers. Head and mesosoma foveolate with no additional sculpture, if additional rugae present then body never yellow (except Pheidole ankerana) (Fig. 9D, E) . . . . . 15

15
return to couplet #14
 * Major workers. Body size small (WL < 0.9 mm); head in full-face view square or subrectangular with anterior and posterior sides of eyes slightly convex, in lateral view sub-oval or sub-rectangular; body bright brown to dark brown (Figs 10E, 11D). Minor workers. Small body size (WL < 0.6mm); head foveolate with no additional rugae; mesosoma entirely foveolate or foveolate with smooth notches on its lateral sides; body yellow (Fig. 9E) . . . . . Pheidole nemoralis species group


 * Major workers. Body size bigger (WL > 1.1 mm); if WL < 0.9 mm then head, in lateral view not sub-oval, if sub-rectangular then in full-face view, square with anterior and posterior sides of eyes relatively straight and body dark brown to black (Figs 10D, 11C). Minor workers. Body larger (WL > 0.6 mm); if WL < 0.6 mm then head foveolate with additional rugae; mesosoma foveolate with smooth notches and additional indistinct rugae; body dark brown (Fig. 9D) . . . . . Pheidole petax species group