The Ants of Africa
groups according to Fischer, Hita Garcia & Peters (2012)
Contents - Myrmicinae - MYRMICINAE Introduction

Genus Pheidole Westwood (1839: 219)

Fischer, Hita Garcia & Peters (2012) recently gave unsubstantiated notes on the genus in the Afrotropical zoogeographical region, with a detailed study of what they termed the Pheidole pulchella group. They made no reference whatever to my work over the previous decade.

Taxonomy of Afrotropical Pheidole species groups

The Afrotropical Pheidole fauna is unlikely to be as species rich as the New World or Oriental faunas. Currently, 136 valid taxa are listed for the Afrotropical region (Bolton & Alpert, 2009), with the actual number of species being undoubtedly higher. Most of the tropical forests and other species rich habitats remain unsampled, and museum collections already store many undescribed species.
We provide diagnostic definitions for six species groups based on morphology. Species within these groups share important characteristics in shape and proportions of head and alitrunk [mesosoma], relative length of appendages in general, and scape and metafemur length in particular. These are related to life history traits and ecology of the species (Weiser & Kaspari, 2006).

Furthermore, important diagnostic characters include postpetiole proportions and modifications (i.e. ventral and lateral processes), and the overall pattern of body sculpture. The latter is generally variable within species groups and between species, ranging from densely punctate to almost completely smooth and shiny. Nevertheless, intraspecifically the sculpture-patterns are consistent, except for some minor and sporadic differences in the expression among different populations. Pilosity is another good diagnostic character, and is suitable for the division of species into groups with major differences in length, thickness, and overall abundance of hairs.

Our species group definitions are provisional and are likely to change when more material is available. The proposed species groups are:

Note: the links are to those species I feel able to recognise. In my list I compare my thoughts with theirs - BT list

P. aurivillii group:
Larger species (minor worker HW: 0.52–0.79 mm, n=52) with relatively long appendages (SI 107–145, FI 142– 247). Minor workers: characterized by oval head that is longer than wide, long promesonotum, declining slowly to metanotal groove, absent or inconspicuous mesonotal process. Sculpture on mesonotum, mesopleuron and propodeum uniform, pilosity relatively long, erect and flexous. Postpetiole with shallow ventral process. Major workers: head with mostly irregular rugose-punctate sculpture. Frontal carinae and antennal scrobe absent or inconspicuous, inner hypostomal teeth developed to large, mesonotal process and postpetiole ventral process present. Pilosity as in minor and very abundant. Four described subspecies (Pheidole aurivillii Mayr, P. aurivillii attenuata Santschi, P. aurivillii kasaiensis Forel, P. aurivillii rubricalva Forel), plus other potentially related species and several undescribed morphospecies probably belong to this group.

P. excellens group:
Species with square-like heads in both, minor and major workers, shorter appendages (minor worker SI 86–115, n=32), often extensive and coarse body sculpture (sometimes only on pronotum), abundant and fine pilosity and small postpetioles, in major workers with a lateral process.
Minor workers: characterized by wide, square head with straight posterior margin and subangulate to angulate corners, relatively short scape, barely to moderately exceeding occipital margin. Postpetiole very short, lower than petiole, about as wide as long. Body often deeply punctate-rugulose/rugose [e.g. excellens Mayr, liengmei Forel], with coarse ridges along dorsopropodeum, but some species mostly smooth [sculpturata rhodesiana Forel], to superficially sculptured [sculpturata]. Usually with high amount of very thin and moderately short body pilosity, often pelt-like, at least on the head. Spines short to long, linearly spinose.
Major workers: head usually elongate, much longer than wide, or at least square-like with parallel to subparallel sides, sometimes wider anteriorly than posteriorly. Submedian and outer hypostomal teeth well-developed to large, median tooth absent. Promesonotal dome high, spines quasi-vertical, often thick, blunt or truncated. Postpetiole laterally with an (often strongly) extended, wing-like, posteriorly curved process. Pilosity and sculpture similar to minor workers.
The group can be subdivided into two different complexes, one with small species (katonae complex; minor worker HW: 0.57–0.63, n=8), possessing short legs and spines, and relatively larger eyes [katonae Forel, sculpturata zambeziana Forel]. The other complex consists of larger species (excellens complex; minor worker HW: 0.69–0.93, n=24), which possess longer legs and spines, and relatively smaller eyes [excellens Mayr, liengmei Forel, njassae Viehmeyer, sculpturata Mayr, sculpturata welgelengensis Forel].
The described species belonging to this group are: Pheidole arnoldi Forel, P. excellens Mayr, P. excellens weissi Santschi, P. katonae Forel, P. liengmei Forel, P. liengmei micrartifex Forel, P. liengmei shinsendensis Forel, P. njassae Viehmeyer, P. sculpturata Mayr, P. sculpturata areolata Forel, P. sculpturata berthoudi Forel, P. sculpturata dignata Santschi, P. sculpturata rhodesiana Forel, P. sculpturata welgelegenensis Forel, P. sculpturata zambeziana Forel. Several probably undescribed morphospecies are located in the collections of BMNH, CASC and ZFMK.

P. megacephala group:
Relatively small species (minor worker HW: 0.51–0.66 mm, n=18), with relatively short appendages (SI 117–122, FI 106–129) and spines.
Minor workers: posterior head margin weakly rounded and eyes with eight or more ommatidia in the longest row. Promesonotum without mesonotal process and often smoothly declining towards metanotal groove, spines very short or minute. Petiole relatively short, postpetiole comparatively large with ventral process.
Major workers: head in full-face view often broadest at mid-point or posterior, anteriorly often narrower, head sometimes slightly heart shaped. Longitudinal rugulae mostly ending on frons, upper half of head usually smooth and shiny, antennal scrobe weak to inconspicuous, inner hypostomal teeth mostly very small or inconspicuous and medium tooth absent. Alitrunk, petiole and postpetiole similar to minor workers.
A number of described species and infraspecific taxa exist for this group [P. megacephala s.s.] (Pheidole megacephala costauriensis Santschi, P. megacephala duplex Santschi, P. megacephala ilgi Forel, P. megacephala impressifrons Wasmann, P. megacephala melancholica Santschi, P. megacephala nkomoana Forel, P. megacephala rotundata Forel, P. megacephala scabrior Forel, P. megacephala speculifrons Stitz, P. megacephala talpa Gerstäcker, P. picata Forel, P. picata bernhardae Emery, P. picata gietleni Forel, P. punctulata Mayr, P. punctulata atrox Forel, P. punctulata spinosa Forel), which is in high need of revision.

P. nigeriensis group:
Very small species (minor worker HW 0.41–0.56 mm, n=60), with short scapes and legs (SI 90–114, FI 95–122).
Minor workers: posterior head margin straight to weakly concave and eyes small with a maximum of six ommatidia in the longest row. Promesonotal dome well-rounded to slightly angulate in profile view, propodeum, spines and postpetiole relatively short. Postpetiole not higher than petiolar node and without ventral process.
Major worker: head longer than wide, very large compared to the rest of the body, anteriorly weakly longitudinally rugulose. Upper half of head mostly smooth (similar to megacephala group), inner hypostomal teeth well-developed to relatively large. Alitrunk, petiole and postpetiole similar to minor workers.
The group contains Pheidole nigeriensis Santschi and several morphospecies collected from different localities.

P. pulchella group:
Relatively large species (minor worker HW 0.66–0.97 mm (n=154), major worker HW 1.63–2.35 (n=53)), with relatively long spines in both, minor (PSLI 21–40) and major workers (PSLI 11–19), which are usually curved backwards, except in P. diomandei.
Minors always with a distinct promesonotal process, followed by a well-developed or conspicuous smaller process (Fig. 1B–4) and a distinctly impressed metanotal groove.
Majors always with a distinct promesonotal process and hypostomal margin of the head always with two conspicuous inner and two outer submedian teeth, but lacking the median process.
Both worker subcastes with a well-developed postpetiolar ventral process, similar to the species of the megacephala complex, but distinctly separated from them by the previous character combination.
Minor workers: head shape in full-face view variable among species, but never square with angulate postero- lateral corners, from short and rounded (CI: 85–98) with sides of head strongly convex, posterior margin convex [dea], or almost straight [rebeccae], to long-elliptical (CI 73–84), sub-angular at eye-level and posteriorly elongate towards occipital carina [christinae, heliosa]. Mandibles smooth and shiny, sometimes with very superficial rugulae, laterally with weak longitudinal rugulae. Eyes situated near midlength of the head, of medium size (EI 19–29). Scapes moderately to very long (SI 102–174) and surpassing posterior head margin by one quarter to approximately one third of their length. Occipital carina always conspicuous in full-face view. Mesonotal declivity interrupted by promesonotal process, followed by a smaller process between promesonotal process and metanotal groove. The second, smaller, process is reduced and less conspicuous in some species. Propodeal spines long and spinose, much longer than distance between their bases (PSLI 21–40), curved posteriorly towards petiole, rarely straight. Promesonotum, in lateral view, with angulate to subangulate edges, pronotal dorsum flat to weakly rounded, never strongly convex. Petiole longer than postpetiole (PpLI 117–223), and in dorsal view usually about half as wide (PpWI 152–232). Postpetiole also with well-developed convex ventral process and about as high as long, with subglobular to globular shape in profile. In dorsal view postpetiole about as long as wide, with a roughly trapezoidal shape. Pilosity with few to many long acute standing hairs, some species with hair apices truncate (or bifurcate), but in some species almost completely absent from dorsum of head, alitrunk and ? metasoma. Mesonotum and propodeum often with shorter, suberect to subdecumbent hairs. Standing hairs never very short and stiff. Between long erect hairs on head often shorter suberect to subdecumbent hairs present. Sculpture variable between species, with relatively little intraspecific variation, from completely and strongly punctate [nimba] to mostly smooth and shiny [rebeccae], but mesonotum and propodeum never completely smooth and shiny, at least partly punctate.
Major workers: head about as wide as long (CI 96–105), broadest always between eye level and occipital margin, frons and sides of head rugose-punctate to varying degrees. Posterolateral lobes often differently sculptured. Dorsal surface of mandible smooth, laterally longitudinally rugulose. Clypeus with median longitudinal carina present. Scapes moderately long (SI: 49–58). Hypostomal margin always with two inner and two outer submedian teeth present, median process absent to inconspicuous. In full-face view, and for all species but P. heliosa, head margin without projecting hairs of any kind, only with relatively short appressed pilosity and long erect hairs, that are visible in lateral view. Pilosity on scape appressed to subdecumbent. Humeral area laterally not or weakly produced, mesonotal process always developed and with posterior steep declivity towards metanotal groove, which, in lateral view, is barely to broadly impressed. Propodeal spines relatively long and spinose, longer than distance between their bases. Petiole longer than postpetiole (PpLI 131–176). Postpetiole considerably wider than petiole (PpWI 177–252), wider and higher than long, in lateral view with anteriorly produced ventral process. Pilosity and sculpture similar to minor workers.
Contents MYRMICINAE Introduction
© 2012 - Brian Taylor CBiol FSB FRES
11, Grazingfield, Wilford, Nottingham, NG11 7FN, U.K.