Pheidole roosevelti

Pheidole roosevelti is quite abundant where it occurs, and foragers can often be observed foraging on the ground and on vegetation. They nest in chambers deep underground in the soil, and the entrance to the nest is a turret approximately 2cm tall and 0.5cm wide that is composed of soil pellets. One nest found on the top of a mountain in Ovalau had three such turrets leading to the chambers below. (Sarnat 2008)

Identification
Sarnat (2008) - Pheidole roosevelti is a large species, most recognizable by the heavy sculpturing present on its face and promesonotum. The two other species with rugoreticulate faces are Pheidole furcata from Kadavu, and Pheidole bula from Viti Levu. In addition to the differences elaborated within the discussions of these other species, the majors and minors of P. roosevelti can be separated by the strongly produced facial rugoreticulum overlying a densely foveolate ground sculpture and thickly rugo-reticulate mesosoma. Unlike P. furcata and P. bula, in which the queen caste is characterized by its smaller size and much reduced mesosoma, the queens of P. roosevelti, with their larger size and strongly developed mesosomas, bear closer resemblance to their northern relatives (Pheidole pegasus, Pheidole simplispinosa).

With the possible exception of P. simplispinosa, P. roosevelti exhibits the most intraspecific variation of any P. roosevelti-group species. Features that vary with high frequency are observed most easily in the minor caste, and include the length, shape and thickness of the propodeal spines, the sculpture of the median face region, the shape of the posterior margin of the face, and the strength of the facial rugoreticulum. A large nest series from Koroyanitu in western Viti Levu reveals that there can be significant variation even within the same colony. The propodeal spines and shape of the posterior margin of the head are two features that vary strongly. The pattern of facial foveolae, in contrast, appears to remain more constant among nest mates. The observed variation in shape and sculpture may, in part, be due to the wide range claimed by the species. Unlike many of its close relatives, P. roosevelti does not appear to be restricted to the upper elevational limits of Fiji’s mountain ranges (Fig. 95), thus allowing its population to span significantly more suitable habitat.

The type series collected by Mann appears to occupy a relatively extreme position in the phenotypic continuum of the species. The faces of the minor workers of the series are characterized by deeply excised posterior margins, coarser foveolae and a smoother median region. The material most closely resembling Mann’s Nadarivatu type series are two workers collected from Mt. Naqaranabuluti, which lies within the Nadarivatu area. The faces of workers collected to the south of the same central mountain range (Monasavu Dam area), however, differ markedly in their narrower nearly flat posterior margins and finer, more extensive foveolae. Despite Ovalau’s current isolation from Viti Levu, the morphological variation observed in material collected from the small island does not appear to be greater between series from Ovalau and Viti Levu than within the Ovalau series. If a characterization is to be made, however, it is that the Ovalau material is more similar to that of the southern and western Viti Levu than to the northern region of the type locality.

Distribution based on Regional Taxon Lists
Indo-Australian Region: Fiji.

Nomenclature

 *  roosevelti. Pheidole (Electropheidole) roosevelti Mann, 1921: 438, fig. 15 (s.w.q.) FIJI IS. See also: Sarnat, 2008: 22.

Worker
Sarnat (2008) - Major. TL 6.01–7.11, HL 2.15–2.38, HW 1.87–2.19, CI 0.87–0.94, FL 1.36–1.44, FI 0.60–0.64, SL 0.90–1.05, SI 0.41–0.46 (8 measured).

Head with sides not distinctly broader behind eyes than in front of eyes. Median ocellus usually absent; when present small and poorly formed. In profile, posterior process modestly produced as a thick upturned lamellate plate; in dorsal view attachment to mesonotum broad to attenuated, posterior margin deeply excised. Propodeal spines maintaining an evenly stout thickness for basal 4/5 length whereupon the anterior edge angles obliquely towards the posterior edge to form an acuminate tip; variation in length of dorsal edge. In posterior view, petiole node dorsum deeply excised. Postpetiole taller than long; subequal height as petiole; steep anterior and posterior faces converging to form an obtusely angulate vertex; in dorsal view subpentagonal with moderate lateral projections.

Region between frontal lobes with straight longitudinal carinae that integrate with a strong rugoreticulum upon reaching vertex; rugoreticulum extends to posterior margin of posterolateral lobes. Intercarinular spaces packed with a dense network of well-defined overlapping foveolae. Median strip of short transverse rugae bisects posterolateral lobes. Crenulate carinae between eyes and frontal carinae. Antennal scrobe foveolate; overlain by short rugae. Clypeus mostly smooth and shining; anterior margin with several carinae extending to frontal lobes; median carina weak to absent. Ventrolateral portion of posterolateral lobes smooth and shining. Head venter rugo-reticulate. Promesonotum rugo-reticulate. Anepisternum rugose. Katepisternum striate. Petiole with apical and posterior faces mostly smooth, laterally and ventrally rugose. Postpetiole anterior face with weak transverse striae; dorsum and posterior face rugulose with foveolate interspaces. First tergite of gaster with long and dense to short and sparse sculpturing basally. First sternite of gaster lightly sculptured laterally. Gaster otherwise smooth and shining. Body reddish-brown with lighter appendages; some individuals with head distinctly more red than body.

Minor. TL 3.48–4.25, HL 0.81–0.90, HW 0.75–0.84, CI 0.91–0.96, FL 1.09–1.27, FI 1.35–1.47, SL 1.04–1.13, SI 1.25–1.32, AE 0.29–0.35, DE 0.20–0.27, PSI 0.60–0.92 (10 measured).

Head, in full face view, subquadrate, sides weakly convex, posterolateral corners rounded and weakly obtuse, posterior margin flat to convex laterally, moderately to strongly excised medially; in profile, posterolateral corners dorsoventrally pinched with carinate margins. Genal carinae moderately elevated on ventrolateral portion of head, terminate without joining together medially on head venter. Clypeus with anterior margin convex laterally, flat to weakly concave medially. Frontal carinae terminating near eye level or integrating with rugoreticulum posteriorly. Mesonotal process produced as a thin lamellate plate with upwardly deflected margins; in dorsal view, attachment to mesonotum broad, posterior margin moderately to strongly concave. Propodeal spines thickening apically into a bifurcation with a short anterior point or angle, and a long acuminate posterior point that projects at an oblique angle; length of dorsal edge less than length of anterior edge.

Head dorsally rugo-reticulate with densely packed foveolate ground sculpture, ventrally smooth and shining without rugae or ground sculpture. Clypeus with a few weak carinae attached to anterior border, weak median carina occasionally present. Promesonotum, in dorsal view, strongly rugo-reticulate. Anepisternum rugose. Katepisternum mostly smooth and shining. Light reddish-brown with slightly lighter appendages.

Queen
Sarnat (2008) - TL 7.43–8.01, HL 1.37–1.52, HW 1.55–1.70, CI 1.12–1.13, SL 1.00–1.05, SI 0.69–0.73, FL 1.38–1.48, FI 0.94–1.03, ML 0.77–0.80, MI 0.91–0.94 (6 measured).

Head subquadrate with sides narrower anteriorly than posteriorly. Mesoscutum, in profile, massive, approximately equal height as pronotum; in dorsal view, obscuring pronotum. Scutellum, in dorsal view, with posterior portion produced as a weakly elevated subtriangular plate. Propodeal spines maintaining an evenly stout thickness for basal 4/5 length whereupon the anterior edge angles obliquely towards the posterior edge to form an acuminate tip. Petiole broadly cuneate; in posterior view, petiole node broad with dorsum strongly excised. Postpetiole, in dorsal view, subpentagonal with moderate lateral projections.

Region between frontal carinae with crenulated longitudinal occasionally branching carinae that become rugo-reticulate near posterior margin. Region between eyes and antennal insertions with elevated crenulated carinae that become rugoreticulate at posterolateral corners; intercarinular spaces densely packed with overlapping foveolae. Head venter rugo-reticulate. Antennal scrobe foveolate. Clypeus mostly smooth and shining; anterior margin with short carinae laterally, median carinae present. Pronotum rugo-reticulate. Mesoscutum, in dorsal view, with straight parallel carinae that run posteriorly towards median. Scutellum rugulose medially, rugoreticulate laterally. Anepisternum rugose. Katepisternum rugose. Petiole rugose. Postpetiole rugo-reticulate. First tergite of gaster longitudinally sculptured basally, sculpture immediately posterior to postpetiole approximately as long as length of postpetiole. First sternite of gaster sculptured basally. Reddish-brown with lighter appendages.

Type Material
Sarnat (2008) - Syntypes, 5 majors, 9 minors, 1 dealate queen. Fiji: Viti Levu, Nadarivatu, (W. M. Mann), ( no. 23173, examined;, examined).

References based on Global Ant Biodiversity Informatics

 * CSIRO Collection
 * Dlussky G.M. 1994. Zoogeography of southwestern Oceania. Zhivotnoe naselenie ostrovov Iugo-Zapadnoi Okeanii ekologo-geograficheskie issledovanii 48-93.
 * Mann W. M. 1921. The ants of the Fiji Islands. Bull. Mus. Comp. Zool. 64: 401-499.
 * Sarnat E. 2008. A taxonomic revision of the Pheidole roosevelti-group (Hymenoptera: Formicidae) in Fiji. Zootaxa 1767: 1-36.
 * Sarnat Eli M. 2009. The Ants [Hymenoptera: Formicdiae] of Fiji: Systematics, Biogeography and Conservation of an Island Arc Fauna. 80-252
 * Ward, Darren F. and James K. Wetterer. 2006. Checklist of the Ants of Fiji. Fiji Arthropods III 85: 23-47.
 * Wheeler W.M. 1935. Check list of the ants of Oceania. Occasional Papers of the Bernice Pauahi Bishop Museum 11(11):1-56.
 * Wheeler, William Morton.1935.Checklist of the Ants of Oceania.Occasional Papers 11(11): 3-56