Pheidole vigilans Fr. Smith 1858

Compiled by Warwick Don & Richard Harris

Biostatus: Introduced

Classification

Family:	Formicidae
Subfamily:	Myrmicinae
Tribe:	Pheidolini
Genus:	Pheidole
Species:	vigilans

Common name(s)

Big-headed ant (Andersen 2002) (Generic common name)

Synonyms (WWW5)

Atta vigilans Smith, Pheidole ampla subsp. norfolkensis Wheeler, Pheidole ampla var. parallela Forel, Pheidole ampla var. yarrensis Forel, Pheidole dolichocephala André, Pheidole ampla norfolkensis Wheeler

Origin

Pheidole is among the largest of ant genera. Wilson (2003) estimates the number of its known species as close to 900, with a large number still to be described. Australia has some 53 species and subspecies. Three of these are established in New Zealand, P. megacephala , P. rugosula and P. vigilans. P. vigilans, like P. rugosula, is of Australian origin.

Distribution

The earliest record of this species (known then as P. yarrensis ) comes from Paihia, Northland, dated 25 January 1949. Since this species is endemic to temperate south-eastern Australia, Berry et al. (1997) see no reason, with respect to climate, why it should remain restricted to northern areas, and more recently (2001) a specimen was collected in Katikati, Bay of Plenty.

General Description

Identification

The workers are dimorphic (major and minor workers). The antennae are 12-segmented with usually a 3-segmented club. In side view the propodeum is depressed below the level of the pronotum and the forward section of the mesonotum, and these two regions are connected by the steeply sloping rear section of the mesonotum. The nest entrance typically has a small mound of soil extracted from the nest.

Diagnostic features of the major worker

Length 5 mm; head massive with the rear (occipital) margin deeply impressed in the middle; rugae (wrinkles in the cuticle) extending halfway from the clypeus to the rear (occipital) margin of the head; propodeal spines (paired) equal in length to the diameter of the propodeal spiracle; colour of head and body reddish-brown, gaster dark brown.

Diagnostic features of the minor worker

Length 2.5 mm; head with rear (occipital) margin shallowly impressed in the middle; head smooth; propodeal spines (paired) equal in length to the diameter of the propodeal spiracle; colour of head and body light brown, gaster darker than body.

Berry et al. (1997) Pheidole species in New Zealand.

Major / soldier caste

[Pheidole vigilans] (major) head. Image: April Nobile (Specimen code: CASENT0172951). www.antweb.org Image — Pheidole vigilans (major) head. Image: April Nobile (Specimen code: CASENT0172951). www.antweb.org

Pheidole vigilans (major) profile. Image: April Nobile (Specimen code: CASENT0172951). www.antweb.org

[Pheidole vigilans] (major) dorsal view. Image: April Nobile (Specimen code: CASENT0172951). www.antweb.org Image — Pheidole vigilans (major) dorsal view. Image: April Nobile (Specimen code: CASENT0172951). www.antweb.org

Minor / worker caste

[Pheidole vigilans] (minor) head. Image: April Nobile (CASENT0172954). www.antweb.org Image — Pheidole vigilans (minor) head. Image: April Nobile (CASENT0172954). www.antweb.org

Pheidole vigilans (minor) profile. Image: April Nobile (CASENT0172954). www.antweb.org

[Pheidole vigilans] (minor) dorsal view. Image: April Nobile (CASENT0172954). www.antweb.org Image — Pheidole vigilans (minor) dorsal view. Image: April Nobile (CASENT0172954). www.antweb.org

Biology

A literature search revealed no details of biology. It can be assumed, however, that the biology of P. vigilans is probably similar to that of the other Pheidole species established here, i.e. it is a generalist.

Pest Status

Not known to be a pest, but collected from urban areas so may be a minor garden nuisance.