Pheidole pallidula

Mostly a west-Mediterranean species, occurring from Italy to Spain and North Africa. Some closely related taxa occur from the Balkans eastwards (see Taylor & Sharaf 2010; Rigato & Toni, 2011).

Identification
Sharaf et al. (2017) - Major worker. TL 3.4–3.9; Head in full-face view subrectangular with moderately deeply impressed posterior margin; clypeus smooth and shining with weak median longitudinal carina; frontal carinae short and feebly divergent; antennae elongate; eyes small and weakly circular; hypostoma with a pair of large lateral teeth; mesosoma in profile with a slightly domed promesonotum; metanotal groove impressed; propodeal spines with small triangular teeth. In profile, petiole with a relatively short pedicel; postpetiole small and globular; gaster distinctly smaller than head; pilosity long, fine and abundant. Body shining; sculpture absent except for fine longitudinal striations on anterior one third of head. Colour overall pale yellowish brown, mandibles dark brown.

Distribution
Pheidole pallidula has a broad distribution in the Mediterranean region (Bernard 1983) and has been recorded from the Iberian Peninsula (Espadaler 1986). Sharaf et al. (2017) report the first record from Socotra Island, Yemen.

Distribution based on Regional Taxon Lists
Afrotropical Region: Socotra Archipelago, Yemen. Palaearctic Region: Afghanistan, Albania, Algeria, Andorra, Armenia, Austria, Balearic Islands, Bulgaria, Canary Islands, Croatia, France, Georgia, Gibraltar, Greece, Iberian Peninsula, Iran, Israel, Italy, Kazakhstan, Kyrgyzstan, Malta, Monaco, Montenegro, Portugal , Republic of Macedonia, Romania, Russian Federation, Slovenia, Spain, Turkey, Turkmenistan.

Behavior
Sempo et al. (2006) examined how the presence of brood influenced the spatial distribution of workers and soldiers within colonies of P. pallidula.

Morphology
Castro et al. (2016) described a stridulatory structure in this species. They used SEM photographs to discern the details they reported.

A pentagonal pars stridens, but in this case the pentagon is inverted, with the apex pointing to the gaster. This shape is much more marked in the major than in the minor forms. Width and length are quite similar, but it is slightly wider (0.08 mm width and 0.07 mm length). Striation is among the thinnest of all the considered species. Pillars are noticeable and thin, with scattered teeth situated mostly in the lateral parts of the stridulatory organs.

Beltra et al. (2017) found this ant forging on grape vines in Eastern Spain vineyards.

Associations with other Organisms
Borowiec and Salata (2015) found that the specimens of the previously described species Pheidole symbiotica were simply workers of Pheidole pallidula that were infested with mermithid nematodes.

Other Insects
Di Giulio et al. (2015) showed the beetle Paussus favieri uses sounds they generate to allow them to live unmolested in colonies of P. pallidula. It had been known that Paussus posses stridulatory organs and while it was suspected this served some role in ant interactions, their purpose had never been investigated. Di Giulio et al. reported "We first characterized the acoustic signals of Paussus favieri and worker, soldier and queen castes of its host ant, Pheidole pallidula. We next analysed ants’ responses to Paussus stridulations by playback experiments and found that the ants react to Paussus sounds, which demonstrates that Paussus stridulations convey an interspecific message. More unexpected, however, was the finding that Paussus beetles were able to produce at least three different acoustical signals that elicited different responses in the ants. We show that Paussus favieri is not only able to mimic ants’ stridulations but can also “speak” three different “languages”, each corresponding to sounds produced by different ant castes, including the queen, to direct host ant behaviours. In effect, Paussus utilizes modular acoustical mimicry to achieve the highest hierarchical status of the colony."

Obregon et al. 2015 - This ant has been associated with the butterflies  Favonius quercus and Zizeeria knysna''.

Worker
Minor

Nomenclature

 *  pallidula. Myrmica pallidula Nylander, 1849: 42 (w.) ITALY (Sicily).
 * [Misspelled as pallidcela by Wheeler, W.M. 1937c: 38, figure caption.].
 * Mayr, 1855: 457 (s.q.m.); Vandel, 1931: 114 (gynandromorph); Hauschteck, 1961: 221 (k.).
 * Combination in Oecophthora: Mayr, 1855: 455.
 * Combination in Pheidole: Smith, 1858b: 173.
 * Junior synonym of megacephala: Mayr, 1861: 70 (in key).
 * Subspecies of megacephala: Emery & Forel, 1879: 463; Forel, 1890a: lxxvi; Emery, 1891b: 13; Dalla Torre, 1893: 94.
 * Status as species: Mayr, 1855: 455; Nylander, 1856b: 97; Roger, 1863b: 30; Mayr, 1863: 441; Emery, 1869b: 19; Forel, 1874: 81 (in key); André, 1874: 198 (in key); André, 1881b: 76; André, 1883b: 383 (in key); Nasonov, 1889: 39; Ruzsky, 1902d: 26; Ruzsky, 1903b: 310; Ruzsky, 1905b: 643; Karavaiev, 1910b: 61; Forel, 1915d: 33 (in key); Emery, 1915j: 226; Wheeler, W.M. & Mann, 1916: 170; Stitz, 1917: 339; Bondroit, 1918: 166; Menozzi, 1921: 26; Emery, 1921f: 86; Müller, 1923a: 69; Müller, 1923b: 67; Wheeler, W.M. 1926: 3; Karavaiev, 1927a: 288; Finzi, 1936: 162; Wheeler, W.M. 1937c: 38; Finzi, 1940: 159; Bernard, 1945: 133; Bernard, 1956b: 258; Bernard, 1959: 346; Baroni Urbani, 1964a: 3; Baroni Urbani, 1964b: 42; Baroni Urbani, 1964c: 152; Cagniant, 1964: 88; Pisarski, 1967: 385; Bernard, 1967: 153 (redescription); Baroni Urbani, 1968b: 446; Pisarski, 1970: 307; Cagniant, 1970a: 417; Baroni Urbani, 1971c: 70; Baroni Urbani, 1976: 211; Tarbinsky, 1976: 68 (redescription); Aktaç, 1977: 121; Arnol'di & Dlussky, 1978: 537 (in key); Collingwood, 1978: 77 (in key); Schembri & Collingwood, 1981: 427; Bolton, 1987: 291; Agosti & Collingwood, 1987b: 272 (in key); Dlussky, Soyunov & Zabelin, 1990: 229; Atanassov & Dlussky, 1992: 123; Arakelian, 1994: 41; Bolton, 1995b: 327; Mei, 1995: 762; Cagniant, 2006a: 197; Radchenko, 2007: 33; Seifert, 2016b: 13.
 * Senior synonym of subdentata: Mayr, 1855: 456.
 * Senior synonym of inquilina: Bolton, 1987: 291.
 * Senior synonym of symbiotica: Borowiec, L. & Salata, 2015: 183.
 * Senior synonym of obscura: Seifert, 2016b: 13.
 * Current subspecies: nominal plus selenia, tasdelenia.
 * subdentata. Oecophthora subdentata Mayr, 1853a: 145 (s.w.) AUSTRIA. Junior synonym of pallidula: Mayr, 1855: 456.
 * symbiotica. Pheidole symbiotica Wasmann, 1909: 693 (footnote), figs. 1, 2 (w.) PORTUGAL. Wasmann, 1910: 515 (q.m.). Junior synonym of pallidula: Forel, 1913d: 430. Revived from synonymy as subspecies of pallidula: Emery, 1915j: 226. Revived status as species: Collingwood, 1978: 68. Junior synonym of pallidula: Borowiec & Salata, 2015: 183.
 * inquilina. Xenoaphaenogaster inquilina Baroni Urbani, 1964b: 50, figs. 15, 16 (w.) ITALY (Sicily). [Unresolved junior secondary homonym of Epipheidole inquilina Wheeler, W.M. 1903f: 664.] Junior synonym of pallidula: Bolton, 1987: 291.
 * emeryi. Pheidole pallidula var. emeryi Krausse, 1912a: 169 (s.w.) ITALY (Sardinia).
 * [Junior primary homonym of Pheidole emeryi Mayr, 1887: 589.]
 * Subspecies of pallidula: Emery, 1921f: 86.
 * Replacement name: Pheidole pallidula var. obscura Santschi, 1936c: 200.
 * obscura. Pheidole pallidula var. obscura Santschi, 1936c: 200.
 * Replacement name for Pheidole pallidula var. emeryi Krausse, 1912a: 169. [Junior primary homonym of Pheidole emeryi Mayr, 1887: 589.]
 * Subspecies of pallidula: Bolton, 1995b: 326.
 * Junior synonym of pallidula: Seifert, 2016b: 13.