The following account is from Sarnat et al. (2015).
Pheidole vigilans is a large, light colored, glossy species native to Australia and introduced in New Zealand. The species belongs to an Old World clade centered in Australia. The glossy head of the majors and minors give it a superficial appearance to P. megacephala, but it is substantially larger than that species. Additionally, the postpetiole of P. proxima is not swollen relative to the petiole as in P. megacephala, and the head of the major is subquadrate, while that of P. megacephala is more heart-shaped. Readers are referred to the section under P. proxima and P. rugosula for a discussion of how to differentiate it from the other Pheidole species established in New Zealand. Additional taxonomy of these species is discussed in (Berry et al. 1997). Within Australia, there are many taxa similar to P. vigilans and its close relative P. ampla Forel. However, a revision of that fauna is required before it can be reliably diagnosed there.
Records show it has established in urban areas and been found with fruit, in gardens, indoors and nesting in failing pasture (Berry et al. 1997).
Pheidole vigilans is not considered a pest in New Zealand, but it has been collected from urban areas and may be a minor garden nuisance (Harris et al. 2005c).
Diagnosis among introduced Pheidole. Smooth yellowish to reddish brown. Major | HW 1.30, HL 1.43, SL 0.68, CI 91, SI 52. Head subquadrate; glossy, lacking foveolate ground sculpture. Posterolateral lobes lacking sculpture (including foveolate ground sculpture, carinae and rugae) posterior to maximum extent of antennal scapes in repose. Hypostomal bridge with two well-developed inner teeth but lacking a median tooth. Promesonotal dorsum glossy, lacking foveolate ground sculpture or striae. Promesonotum in profile forming a single dome, lacking a distinct mound or prominence on the posterior slope. Metapleuron almost completely glossy with strongly reduced carinulae and lacking punctation. Petiolar node mostly glossy, not covered by punctate sculpture. Postpetiole not swollen relative to petiole. Minor | HW 0.55, HL 0.58, SI 0.55, CI 95, SI 101. Head predominantly glossy, lacking punctation and or rugae above eye level. Antennal scapes surpass posterior head margin by approximate distance of eye length. Mesopleuron entirely glossy. Promesonotum in profile forming a single dome, lacking a distinct mound or prominence on the posterior slope. Propodeal spines weakly produced and dentiform. Petiole almost entirely glossy. Postpetiole not swollen relative to petiole.
Pheidole vigilans is considered endemic to the south eastern corner of Australia (Brown 1971). Heterick et al. (2013)reported P. vigilans as introduced to Perth in Western Australia. The species was first collected outside of Australia in Kerikeri, New Zealand in 1956, and remains the least frequently collected Pheidole species in New Zealand (Berry et al. 1997; Cumber 1959). Although Pheidole ampla subsp. norfolkensis Wheeler was originally described as endemic to the Norfolk Islands, Brown (1971).