Threat Level: Low

Pheidole oceanica is a common species in the Pacific with two waist segments, 12-segmented antennae, 3-segmented antennal clubs, propodeal spines, long thin pilosity, and a bimorphic worker caste. The minor workers are small, pale to dark and have long legs and long antennal scapes, very small propodeal spines, and no antennal scrobes. Sculpture on the minor worker is restricted to the middle and posterior portions of the mesosoma. The major workers are larger, darker and are have oversized, heavily sculptured heads. The majors also have distinct antennal scrobes and longer propodeal spines than the minors.

Pheidole fervens is easily confused with P. oceanica. The major workers can be distinguished most reliably by the sculpture located between the eye and the antennal insertions. Whereas the carinae of P. fervens are branched, those of P. oceanica are unbranched. Also, the antennal scrobes of P. fervens are more densely punctate than those of P. oceanica. The minor workers of P. oceanica are especially difficult to differentiate from P. fervens. Whereas the propodeal spiracles of P. oceanica are smaller than the propodeal spines, the propodeal spiracles of P. fervens are equal to or larger than their propodeal spines.

Pheidole megacephala can be separated from P. oceanica by more obvious means. The heads of P. megacephala major workers lack antennal scrobes are are almost entirely absent of sculpture. The minor workers have shorter antennal scapes and a more swollen appearing postpetiole.

Pheidole oceanica is described by Wilson and Taylor (1967) as being native to the Pacific region, and not being an invasive ant. The species is included in PIAkey because of its close morphological resemblance to P. fervens. It should also be noted that this species demonstrates a considerable amount of morphological variation with respect to size, color and sculpture. Pheidole oceanica recruits strongly to baits and food resources and forms long and busy foraging trails. Minor workers are much more abundant than major workers, both outside of and within the nest.

Pheidole is the most diverse ant genus in the world, and many native and widespread species occur in the Pacific that are not included in PIAkey. If the specimen under investigation does not match any of the PIAkey Pheidole, explore images from Antweb and taxonomic literature pertaining to Pacific ants.

Table 1. Minor worker
Table 2. Major worker

Table 1. Minor worker

Waist with two segments (petiole & postpetiole)
Propodeal spines present
Antennal club with three segments
Antennal scrobe absent
Slope of mesosoma steep
Head size normal relative to body size
Postpetiole not swollen compared to petiole (for an example of a swollen postpetiole, see P. megacephala)
Antennal scapes relatively long
Propodeal spiracle equal to or larger than propodeal spine

(top of page)

Table 2. Major worker

Waist with two segments (petiole & postpetiole)
Propodeal spines present
Antennal club with three segments
Head size disproportionately large relative to body size
Antennal scrobe present
Slope of mesosoma steep
Posterolateral lobes with sculpture present
Sculpture between eyes & antennal insertions unbranched

Chart 1. Minor workers

 

	P. oceanica	P. fervens	P. megacephala
Head
Profile
Postpetiole relative to petiole	not swollen	not swollen	swollen
Antennal scapes relative to head width	~ 1.5x	~ 1.5x	< 1.5x
Propodeal spiracle	greater than propodeal spine	smaller than or equal to propodeal spine	(not applicable)

(top of page)

Chart 2. Major workers

 

	P. oceanica	P. fervens	P. megacephala
Head
Profile
Sculpture on posterolateral lobes	present	present	absent
Antennal scrobes	present	present	absent
Ridges between eye & antennal insertion	unbranched	branched	(not applicable)

• Antweb: specimen images, data & maps
  
  
• Bolton, B. (1995) A new general catalogue of the ants of the world. Harvard University Press, Cambridge, Massachusetts, 504 pp.
  
  
• Wilson, E.O. & Taylor, R.W. (1967) The ants of Polynesia (Hymenoptera: Formicidae). Pacific Insects Monograph, 14, 1-109.