Pheidole megacephala (Fabricius)

Iran list Type location not known (Formica megacephala, Fabricius, 1793: 361, major) [note Wheeler, 1922, has the type locality as Mauritius = "Isle de France", as per the specimen label, see photomontage on the linked majors page (see below); but Forel, 1891: 176, reckoned the location was Madagascar]
Subspecies (Bolton,1995)
duplex (Pheidole megacephala F. v. duplex n. var., Santschi, 1937d: 218, major, minor & queen) from Angola - see http://www.antweb.org/specimenImages.do?code=casent0906513 appear identical to the fresh specimens I have (linked pages)
junior synonyms
perniciosa (Oecophthora perniciosa, n. sp., Gerstäcker, 1859: 263, minor; junior synonym of megacephala, Emery, 1915j: 235) from Mozambique - see (headless) http://www.antweb.org/specimenImages.do?code=casent0906517
laevigata (Myrmica (?) laevigata sp. nov., F Smith, 1855b: 130, illustrated, minor; junior synonym of pusilla, Roger, 1859: 259, of pallidula, F Smith, 1858a: 282; of megacephala, Roger, 1863b: 30; of pusilla, Emery, 1915j: 235) from Great Britain, collected at Battersea [also name used by Mayr, 1862: 747, minor, for specimen from Brazil]
scabrior (Pheidole megacephala var. scabrior nov. var., Forel, 1891b: 178, major, minor, queen and male) from Madagascar; see linked page; the major matches the light coloured major I have from Kenya 2010-02; the minor matches the Kenya 2010-10.
speculifrons (Pheidole megacephala F. v. speculifrons n. v., Stitz, 1911b: 386, major & minor) from Tanzania, Bukoba - on linked pages (see below)
suspiciosa (Myrmica suspiciosa, F. Smith, 1859a: 148, minor; junior synonym of megacephala, Donisthorpe, 1932c: 455) from Indonesia, Aru - see http://www.antweb.org/specimenImages.do?code=casent0901409.
testacea (Atta testacea, F Smith, 1858b: 168, major & minor; junior synonym of megacephala, Brown, 1981: 530) from Brazil .

Note Fischer & Fischer (2013) designated a "neotype"; I feel that was unnecessary given that good specimens of the junior synonyms exist, e.g. duplex.   
[Fischer, G.; Fisher, B. L. 2013. A revision of Pheidole Westwood (Hymenoptera: Formicidae) in the islands of the Southwest Indian Ocean and designation of a neotype for the invasive Pheidole megacephala. Zootaxa 3683:301-356.] It, perhaps, is worth noting that although they examined many specimens, from Africa they listed only a few samples from East Africa and very few of the listed types of their junior synonyms.

Fabricius's (1793) description is at . F Smith's (1855b) description of laevigata (worker) is at . F Smith's (1859a) description of Myrmica suspiciosa (worker) is at . Gerstäcker's (1859) description of perniciosa (worker) is at . Forel's (1891b) description of megacephala and varieties from Madagascar is at and . Forel's (1907g) description of ilgi is at . Stitz's (1911b) description of speculifrons is at . Emery (1915j) sought to clarify the megacephala-group of species, with notes and illustrations - see . Emery (1919a) gave notes and illustrations - see . Arnold's (1920a) translation of ilgi (as ilgii) is at . Santschi's (1937d) description of duplex is at .

It seems clear that the form described as megacephala by Latreille (1802; with illustration from Coquebert, 1798 http://gallica.bnf.fr/ark:/12148/btv1b23002416/f6.item), Losana (1834) and then Mayr was actually the circum-Mediterranean species Pheidole pallidula (Nylander). The Coquebert drawing, however, is labelled Formica megacephala F. and the title of the overall work states the insects are from the Museum in Paris and described by Fabricius

Illustratio iconographica insectorum quae in Musaeis parisinis observavit et in lucem edidit Joh. Christ. Fabricius, praemissis ejusdem descriptionibus. Accedunt species plurimae, vel minus aut nondum cognitae, auctore Antonio Joanne Coquebert, 1798-1801. - [Illustrations de Illustrato iconographica insectorum...] [Image fixe numérisée] / A. J. Coquebert, dess. ; Maleuvre, grav., 1798-1804

Emery (1915j: 236) related how the type of Formica megacephala was described by Latreille in 1802 from specimens living in Paris, that is to suppose the "l'île de France", was in the Bosc collection kept in the Paris Museum. He, Emery, had asked Mr L Berlaud to look for the type but it could not be found. Emery noted that in view of the confusion and lack of the type or "topotypes" he maintained the name Ph. megacephala (F.) but without formally designating a type. He made no reference to the Coquebert drawings of a major, an alate queen and a dealate queen.

Latreille's (1802c: 232) illustrated description is at . Losana's (1861) description is at . Mayr's (1861) description is at .

Notes - changes from the Bolton (1975) listing:

• costauriensis - Bolton (1995: 320) had Pheidole rotundata st. costauriensis as "Subspecies of megacephala: current status". Santschi's (1914a, 1915c) descriptions of Pheidole rotundata stirps costauriensis, coupled with Emery's (1915c) drawing of melancholica and my own drawings of "P. crassinoda" have led me to elevate Pheidole costauriensis to species.
• edax - the junior synonym edax (Formica edax, Forskål, 1775: 84, worker) from Egypt (no images on Antweb, November 2014) is more likely to be a variety of Pheidole pallidula as wide surveys of Egypt have never definitely found P. megacephala.
• ilgi - this clearly is, as originally described, a subspecies, probably junior synonym, of Pheidole rotundata (Pheidole rotundata Forel, subsp. Ilgi n. subsp., Forel, 1907g: 82, major & minor; Forel, 1907c: 139, queen & male; subspecies of megacephala, Emery, 1915j: 236) from Ethiopia, Harar, collectors Ilg & Ratgeber, also from Pemba Is, Dr Voeltzkow
  
• janus - from the illustration it has to be said that janus is not a megacephala variety nor would it be P. teneriffana; it seems Wheeler (1922: 812) was responsible for the errors in synonymy. Pheidole janus may well merit revived species status but is extralimital to this website (no images on Antweb, November 2014) .
• melancholica - I also regard Pheidole melancholica (Santschi, 1912b), from Ivory Coast, as a distinct species in the crassinoda-group.
• nkomoana - Forel (1916) felt Ph. megacephala new strips nkomoana could well be a separate species. With my own description and drawings of "Pheidole species E", I have raised Pheidole nkomoana to species status.
• pusilla - on examination of the description and illustration of pusilla (Oecophthora pusilla, Heer, 1852: 15, illustrated, all forms; also illustrated by Emery, 1919a) from Madeira (with junior synonyms janus, F Smith, 1858b: 175, illustrated, soldier & worker) from Sri Lanka are clearly not megacephala; pusilla appears to be a distinct species Pheidole pusilla and I have transferred it there.
• talpa - I agree with Dalla Torre (1893: 95) and Emery (1915j: 235) that Pheidole talpa (Gerstäcker, 1871: 356, soldier; Santschi, 1930b: 67, minor & queen) is a junior synonym of Pheidole punctulata and not of megacephala as thought by Santschi (1925h: 160) and listed in Bolton (1995: 331) - note specially the rhomboid pronotum with acute angles, characteristic of punctulata.
• trinodis - from the original description by Losana (1834), it seems obvious that trinodis (Myrmica trinodis, Losana, 1834: 327, illustrated, worker; synonymy Roger, 1863: 30) from Italy, see , is not a junior synonym of megacephala and is not even a Pheidole - Losana emphasises the presence of four spines on the propodeum, i.e. possibly it was a Tetramorium. The confusion by Roger (1863b: 30, followed in Bolton, 1995) probably was caused by Losana's immediately following description of specimens of "the megacephala of Latreille" - as Losana wrote of the ant as nesting in our garden, in Piemonte (Piedmont), in northwest Italy, he almost certainly was reporting on Pheidole pallidula; note his description of a lion-coloured ant.

Note - Forel (1891: 176) reckoned the location was Madagascar but Wheeler, 1922, has the type locality as Mauritius = "Isle de France". The Antweb site specimen with the code CASENT0101411 is a major worker with the labels "TYPE" and "Mauritius (Ste Catherine). Collected by Linden" from the Paris Museum (see the major workers page). Emery(1915c), however, had a note that M. L. Berlaud had searched the collection Bosc in that Museum and could not find the Fabricius type specimen. Most of the Dom. Bosc. specimens listed by Fabricius were from "Cajennae", that is Cayenne, French Guiana, with a couple from Senegal but no other from the "Isle de France". The confusion may have a simple answer. In the 18th Century the "Isle de France" was the region centred around Paris and Louis Augustin Guillaume-Bosc was a French naturalist, primarily a botanist, who prior to 1793 appears to have studied and worked at the "Jardin des Plantes" in Paris. Emery also related how it was Roger who had specimens from Mauritius but if those specimens were in the Berlin Museum which held some of Roger's collection they no longer existed. Given that F Smith collected minor workers of P. megacephala from Battersea in England, it seems quite possible Bosc also had encountered specimens imported on plants from the tropics. A Jean Jules Linden was a 19th Century explorer (see http://en.wikipedia.org/wiki/Jean_Jules_Linden, accessed 16.iii.2011) but seems unlikely to have been the collector of the Pheidole specimen. However, there also was a Belgian Hymenopterist, Pierre Léonard Vander Linden (1797-1831) who collected insects during a journey from Paris to Bologna in 1817; whilst in Paris or on the journey there he met Latreille  (http://www.fsagx.ac.be/zg/Publications/pdf%20zoologie/1301-1350/1331.pdf).

Strickland (1951a) describes it as abundantly common in Ghana (Gold Coast) cocoa farms. He described it as essentially ground-nesting but added that no attempt was made to distinguish between its numerous varieties and subspecies. An interesting observation was how it was able to repel Crematogaster africana and carry off mealybugs attended by that ant. Curiously, the other more recent reports from Ghana make few references to the species. It was reported from the Mamfe-Mampong cocoa farm in Ghana by Room (1971), but he collected it only on herbs and on the ground; and it plays no part in his report of the ant mosaic. Seventy-seven workers were collected by pkd from the canopy of Amelonado cocoa at CRIG by Bigger (1981a), at a guess these came from a single nest. Strickland (1951a) noted findings on other plants, including plantain (Musa sapientum). Evans (1973) described its role as a vector of Phytophthora pod rot of cocoa in Ghana, but seemed to regard it as most important along the edge of farms and probably most significant early in the season.

Its role as a vector of cocoa black pod disease was confirmed by Babacauh (1982) by experiments at the national School of Agriculture, Abidjan, Ivory Coast. It was soil nesting ants which made tents of soil that acted as vectors and the homopteran involved as an attractant was Planococcoides njalensis.

In the CRIN collection, I separated out what appeared to be a melanistic variety, Pheidole species T³. This was morphologically almost identical but the head of the soldier was slightly more rugose and the minor was very dark with yellow antenna and tarsi. It seemed also to be the more common of the two varieties on unshaded vegetation. This may well be Pheidole pusilla

Hall, Cushman et al. (1998) described how ant-tended homopterans indirectly benefit figs (genus Ficus) across southern Africa (Madagascar, Malawi, South Africa, Zambia and Zimbabwe). The most common ant was Pheidole megacephala found on 58% of sampled trees, tending particularly the homopteran Hilda patruelis (Tettigometridae), found on 47% of the fig trees. They noted that they had found the ant also on fig trees in Cameroun.

Oxford University Museum specimens

Major workers - also see comparison page

Nigerian specimens (Taylor, 1980a: 15). MAJOR ( (apparently somewhat smaller than usual) TL 3.58, HL 1.17, HW 1.24, SL 0.68, PW 0.61
Colour red-brown, gaster darker, appendages lighter. Alitrunk spiculate except for posterior dorsal and lateral areas of the pronotum. Erect hairs relatively long and moderately abundant. Clypeal margin medially concave. Propodeal spines short and acute.

In the CRIN collection, I separated out what appeared to be a melanistic variety, Pheidole species T³. This was morphologically almost identical but the head of the soldier was slightly more rugose and the minor was very dark with yellow antenna and tarsi. It seemed also to be the more common of the two varieties on unshaded vegetation. The variant now has been collected in Benin and major and minor workers are shown on the comparison pages.

The photomontage is of a major worker from Gabon, Pongara National Park, Pointe Wingombé; collector Yves Braet (Gabon 29).

Minor workers - also see comparison page

Fragmentary remains of perniciosa can be seen at http://www.antweb.org/specimen.do?name=casent0906517 . These seem identical to the regular minor worker.

Nigerian specimens (Taylor, 1980a: 15)
MINOR TL 2.49 mm, HL 0.67, HW 0.58, SL 0.68, PW 0.39
Colour red-brown, gaster darker, appendages lighter. Erect hairs relatively long and moderately abundant. Clypeal margin relatively shallowly convex. Shiny, with only sculpturation on mesonotum, propodeum and petiole, all of which are densely spiculate.

Minor from Gabon.

Wheeler (1922) listed megacephala s.s. from Gambia (Dakar, F. Silvestri) and Cameroun (Sjöstedt); costauriensis from Guinea (Kindia and Kakoulima, F. Silvestri) and Nigeria (Ibadan, F. Silvestri).

Excellent illustrations can be seen on the Japanese Ant Color Image Database.

Collingwood (1985), describing specimens he recorded from Saudi Arabia, included the illustration right of the pedicel dorsum and base of the funiculus. He noted promoseonotal outline evenly curved without a distinct mesonotal prominence and funicular segments 2, 3 & 4 not longer than broad.

Bernard (1952) writing on the Guinea findings from Mt. Nimba, urged caution when it came to defining new species. He reported megacephala senus stricto from Gouéla, T 91, grassland at 1600 m (Lamotte), moderately common. Far more abundant was the race melancholica, with a larger and more indented head than the other races (somewhat similar to Pheidole picata but that has a more slender thorax); It was found in the savanna at Yalanzou, Nion, Ziéla and Kéoulenta; and from the forest at diverse altitudes, specially on the crests at 1300-1600 m (where the greatest numbers of soldiers and 2 alated queens were found). He noted the subspecies as known from Guinea, Ivory Coast, Ghana and Nigeria, with varieties from Zaïre and eastern Africa; and described the queen (hitherto undescribed). I have separated Pheidole melancholica as a distinct species, in the crassinoda-group.

Nests in ground or soil in crevices on trees. As well as the abundant findings on cocoa, it was found foraging on native trees, cashew, coffee, kola, oil palm and plantain.

One of the commonest and the most widespread ant species on cocoa in Nigeria, dominant on 12-14% of cocoa trees throughout the cocoa growing area (Taylor, 1977; Taylor & Adedoyin, 1978). Avidly tends Homoptera, of all main types, and constructs tents of soil, plant or arthropod debris or a combination. The tents, especially those constructed of soil, were frequently associated with cocoa black pod infections and because of this, the ant may be one of the main sources of the onset of the black pod epidemic (Taylor & Griffin, 1981). Climb high into the trees, up to 320 cm, making debris tents above about 150 cm.

Male from Congo.

Notes

This may be one of the world's most widely distributed, and perhaps most ubiquitous, tropical species. Hölldobler & Wilson (1990, page 118) picture specimens, from the Pacific Island of Samoa, which look very similar to those I have drawn. They also remark on it being notable for high local abundance and that it often 'extirpates' many other species of ant (pages 399-400). The drawing is from Wilson's (2003) review of the Pheidole of the New World.

There are a number of examples shown on the Antweb pages at https://www.antweb.org/images.do?rank=species&genus=pheidole&name=megacephala.
The queen shown at http://www.antweb.org/specimen.do?code=casent0055887, however, seems to be an example of Pheidole fervens.
The major at http://antweb.org/specimen.do?name=casent0101767 is the distinct species Pheidole picata from Madgagascar.