Pheidole pusilla (Heer) - revived status

Major - Minor - Type location Madeira (Oecophthora pusilla, Heer, 1852: 15, illustrated, all forms; also illustrated by Emery, 1919a). Note - the form listed in Bolton (1995: 323) as pusilla junior synonym janus (Pheidole Janus, F Smith, 1858b: 175, illustrated, major & minor) from Sri Lanka clearly is neither fervens nor megacephala.

Heer's (1852) description of pusilla is at . F Smith (1858b) gave illustrated descriptions of pusilla and janus; these are at . The latter, however, is clearly not a junior synonym of pusilla. Mayr (1861) separated pusilla from megacephala and this is as at . Mayr (1870) separated pusilla from among American Pheidole as at . Mayr (1870) referred to P. laevigata as synonymous with pusilla, his laevigata description (Mayr 1862: 747) is at .

The synonymy of pusilla under Pheidole megacephala was ascribed by Bolton (1995: 328) to Wheeler (1922a: 812). This was wrong. Wheeler, gave no indication of sighting any material other than the specimens collected by the Congo Expedition and probably relied on the interpretation by Emery (1915j: 235, and 1919a: 170, to correct publishing errors with the images in 1915j). Emery had pusilla as "Ph. megacephala ... Subsp. (Typique?) pusilla Heer, 1852". The collection of "pusilla" heads shown by Emery (1919a) show two distinct shapes - the broader less anteriorly narrowed form from Antille Saint-Thomas indeed matches the megacephala type shape but the Madere (Madeira) and Teneriffe shapes quite clearly are distinct. Emery (1915j) tried to sight the type specimens of pusilla and megacephala but neither could be located. According to Emery, it was Roger who had associated the two but it seems clear that Roger made his association purely on the descriptions. On a point of correctness, Emery noted the name pusilla had been used by De Geer in 1773 for a ant he named as Formica pusilla that probably was a Pheidole. Mayr (1861) separately described both pusilla and megacephala giving a key to separate them. Bolton (1995: 202) noted Formica pusilla, type location Surinam, as unidentifiable to genus. Wheeler (1927) wrote of Heer's finding "the island (Madeira) overrun by Pheidole megacephala susp. pusilla".

A historical curiosity is the listing in St. Helena by J C Melliss, 1875.

177 ORDER HYMENOPTERA. Fam. Poneridæ. Pheidole, Westw. P. pusilla, Westw.—The common, small, red Ant is identical with the house Ant of Madeira, and is also found in London. Without exception it is the most abundant insect at St. Helena, where it exists in swarms on both high and low land. Most houses are plagued with it, more especially in wet weather, when it is driven indoors. It attacks everything and even finds its way into beds, hats, brushes, and clothing. Out of doors it exists in colonies under stones on barren land, where it is difficult to dis­cover what it feeds upon. A colony generally consists of five distinct forms of inhabitants. First, there are large numbers of the ordinary-sized ants or workers ; second, a lesser number of larger ants, about one-third of an inch long; third, a lesser number again of still larger ants, about half an inch long, which appear to be females ; fourth, a moderate number of winged ants ; and fifth, a large number of transparent white eggs or larvæ. When one of these settlements is disturbed, the small ants or workers rush about most frantically, each laying hold of and carrying away one of the larvæ. There is another species which appears to be confined to the town; it is slightly larger, quite black, and more active in its movements.[http://www.bweaver.nom.sh/j_melliss/jmelliss.htm in part 3;http://www.bweaver.nom.sh/j_melliss/jmelliss-pt3.htm]

Comparing the majors of the usually recognised species, Pheidole fervens and Pheidole megacephala with Heer's description and drawings lead me to conclude that pusilla is a distinct species, probably endemic to West Africa & the Congo Basin, and that the fresh specimens shown below (major & minor) are a match. The form and positioning of the hypostomal teeth (not described by Heer), moreover, sets pusilla apart from both megacephala and teneriffana.

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. These may well have been Pheidole pusilla.

MAJORS

Illustration of Oecophthora pusilla from Madeira, Heer (1852).

Translation of Heer's description by Hauke Koch -
4. Major [Soldier] Fig III, 1 natural length; 2 and 3 ten times enlarged. Total length: 2 lines [4.23 mm]; head length ¾ line [1.6 mm] , head width 5/8 [1.32 mm], alitrunk length ¾ line [1.6 mm]; gaster length ½ line [1.06 mm], likewise the gaster width. Differing from the worker by being twice as large; head striated, with occiput scalloped, with shorter, stouter mandibles, of which the inner margin is not toothed, and the slightly larger gaster. The slightly hairy head is of remarkable size and the occipital margin much deeper scalloped than in the female, thus almost heartshaped. A deep longitudinal groove crosses its middle. The feeler grooves [scrobes] are rather deep, especially at their frontal end and they are separated from the frons by a rather heavily prominent ridge. The frontal part of the frons has a similar, deep impression as in the female; The clypeus is very short and seperated by a fine line from the head. The dorsum of the head is covered with fine longitudinal stripes, as in the female; deep stripes blur behind the middle of the head, so that the occipitum is totally smooth. The eyes are small and the ocelli are missing. The mouth parts are similar to the female's and in fact as well the mandibles, only that at the cutting edge there are some very small, teeth with a bristle (Fig. III., 4). The antennae are as in the female; the scape is much shorter than the head; the three last segments (Fig. III. b) conspiciously separated. The alitrunk has a similar construction as in the worker, only that the mesonotum is much more widened the middle and it shows to both sides a hair, equipped with a bristle, thus differing from the female and worker. The scutellum is almost square; the hind part of the propodeum is armed to both sides with a sharp spine and has a longitudinal groove in the middle. All of the alitrunk is equipped with separate hairs. The legs are larger than in the worker, otherwise of the same shape. The gaster is much smaller than the head. The petiole is enlarged in comparison to the worker by a protruding, scalelike hump with a cluster of hairs; the postpetiole is shorter and thicker, than in the worker and comes close in in its shape to that of the female. The first segment of the gaster is the largest, the second quite of the same width, but shorter; the third apically rounded; the fourth is very small and almost inserted in the latter. The gaster is entirely smooth and shiny, sparsely equipped with fine hairs, which are longer and denser at the hind margin. The head is sometimes lighter, sometimes darker brown, always lighter on the ventral side than on the dorsal. The clypeal margin and the mandibular apical margin are black; the antennae and legs are light yellow; the alitrunk and pedicel slightly lighter brown than the head; the gaster with the same colour at the base and apex, but the second and third segment black brown. Sometimes the black-brown protrudes further, to the hind margin of the first segment, but more often it retreats further, so that it forms only a small band over the hind margin of the second segment and the third segment.

Major
The photomontage is of a major collected in Cameroun, at Banyong Mbo, by Hauke Koch, 11.iii.2006, from debris in Campylospermum axils. Other images can be seen in the folder at -

This shows all the features described and shown by Heer - the head has extensive longitudinal striations, petering out towards the occiput, with long frontal carinae and a well marked scrobe area; the mandible has the double large teeth and distinct margin area, with quite prominent hairs; the denticles are each surmounted by a bristle (absent totally in megacephala); the apex of the funiculus has the three elongated segments, each with convex sides; the dorsum of the propodeum has a distinct longitudinal groove or impression; the postpetiole is quite narrow; seen from slightly above and behind the head shows the quite deep impression of the occiput and (from that angle) the scapes appear of the same order of length.

MINORS

Translation of Heer's description by Hauke Koch -
3. Minor [Worker] Figure IV. 1, natural length; 2, ten times enlarged. Total length 1 1/8 line [2.38 mm]; head length 3/8 line [0.80 mm], head width likewise; alitrunk length ½ line [1.06 mm], gaster length ¼ line [0.53 mm - 1 line = 2.117 mm]. The head is slightly bigger than the gaster. It is totally shiny, smooth and hairless. The insertion area of the antenna is indeed characterised by a rather deep groove and the frontal margin of the frons is as well impressed; the striations, in contrast, that we can find on the head of the females and soldiers, are entirely missing. The mandibles (Fig. IV. 3) are comparatively longer, but more narrowed at the base, than in the females and soldiers and are thus obtaining a more delicate shape; the two teeth at the apex are longer a lot more pointed and the entire inner margin is equipped with a row of teeth, their number varying between 10 and 12. These teeth are arranged very regularly giving the mandibular margin a sawn appearance. The teeth of the mandibles are interlocking and are thus explaining to us how these small animals are capable of holding and carrying such heavy loads with their mandibles. The remaining mouth parts are similar to that of the female. The antennae (Fig. IV. 4) are comparatively a lot longer than in the female and soldier; their scape is protruding considerably over the occipitum; but otherwise there are similarly shaped. The ocelli are missing. The alitrunk is very narrow. The dorsal pronotum is very subtly granulated. The dorsal mesonotum is in the middle somewhat widened; it is totally smooth and shiny; the scutellum and the dorsal propodeum however are very subtly (only observable under the microscope) granulated; the later is equipped on both sides with a small spine. The legs are similar to that of the female, but much smaller (Fig. IV. 5.7); They have very delicately constructed feet, meanwhile they have sharp claws, and between them are visible ariolae (Fig. IV. 6). They are finely pubescent. The postpetiole is comparatively longer and narrower than in the female. The gaster is very small and short oval. The first segment protrudes approximately to the [[illegible]] of the body and is much larger than the second. The head is sometimes lighter, sometimes darker brown; the alitrunk, scapus, femur and tibia are light-yellowish-brown. Funiculus and tarsus are light yellow. The shiny gaster is chestnut-brown, [illegible (with lighter?)]] ground and apex.

The photomontage is of a minor collected in Cameroun, at Banyong Mbo, by Hauke Koch, 11.iii.2006, from debris in Campylospermum axils. Other images can be seen in the folder at -

This shows all the features described and shown by Heer - the head is without striations, but the antennal insertions are inset and the frontal area distinctly impressed; the mandibles are long with a saw-like set of teeth and overlap; the sculpturation, including the faint spiculation on the mesonotum is present.

The photomontage is of specimens collected in Cameroun - south-western tropical coastal forest area between Edéa and Campo (McKey Wolbachia project) - Cameroon 73 from location BOU (Bondé - river near N'kolobondé at 3°13.31' N 10°15.01'; flat land, between the Chapel and the river), 18 April 2001, nest on a big tree under bark comprised of large scaly plates.

Minor (five specimens) very slender and elongated; dark yellow-brown; funiculi, forecoxa, base of all femora and tarsi yellow. Elongated but ovoid head with frontal carinae distinctively raised and extending forwards in points (similar to those in Pheidole nimba). Clypeus with extended triangular rear border and near straight but medially impressed anterior border. Head almost unsculptured and shiny. Eyes large, convex and set forwards of the midline of the face. Scapes long and slender; funiculus with segment 9 and 10 subequal and almost as long as apical segment 11. Well developed nuchal collar. Dorsum and lateral pronotum shiny and near unsculptured but some spiculation on pronotal shoulders; mesonotum, propodeum and petiole with dense spiculation. Propodeal spines short and triangular with sharp tips. Petiole with a rectangular apex in frontal view; postpetiole globulose. Gaster completely smooth and shiny. Legs long with very slender tarsi. Moderately long, fine, erect hairs on head, scapes, pedicel and gaster giving a bristly appearance, especially to scapes. Other images can be seen in the folder at -

Minors from Gabon Pongara Nationa Park; Pointe Wingombe; 9-25.vi.2006; Malaise trap under trees; collector Yves Braet. Other images can be seen in the folder at - and .

On the queen, Heer gave drawings and Mayr (1861) separated the queen from megacephala as having sharp teeth on the propodeum and a sharp tooth under the postpetiole. Heer's drawing indicates a generally matt appearance, unlike the shiny P. megacephala, and the same double edged mandible as the major worker. The specimen of a P. megacephala queen published on, e.g. http://antweb.org/specimen.do?name=casent0104406&shot=p1&project=null, etc. has much larger eyes than in Heer's drawings, in his description, Heer notes the "rather small eyes". The Heer queen has scapes surpassing the occiput, and, from the drawing, longer funiculi and (as Mayr remarked) sharper propodeal spines.

Heer gives the male as the length of the major and coal-black - see the P. megacephala male at http://antweb.org/specimen.do?name=casent0104409&shot=p1&project=null