Threat Level: Low

Tetramorium tonganum is a small orange ant. This species has a monomorphic worker caste with 12-segmented antennae, three-segmented antennal club, antennal scrobes, short antennal scapes that do not surpass the posterior margin of the head, a gradually sloped mesosoma, and moderately long propodeal spines. Like all myrmicines, T. tonganum has two waist segments and a gaster armed with a stinger.

There are five additional Tetramorium species that are spread across the Pacific Island region. Tetramorium insolens can be distinguished from these by the combination of the following characters: (1) a rounded petiolar node and a long thin petiolar peduncle, (2) moderate length propodeal spines, (3) sparse long thin pilosity, and (4) uniformly orange color.

There are many other myrmicine genera that appear similar to Tetramorium. Pheidole species can be distinguished by their polymorphic worker caste. The major workers have disproportionately large heads, and the minor workers have long antennal scapes that extended beyond the posterior margin of the head and lack antennal scrobes. The mesosoma of the majors and minors are more steeply sloped than those of Tetramorium. Cardiocondyla species lack antennal scrobes. Wasmannia auropunctata has 11-segmented antennae with two-segmented antennal clubs.

Tetramorium tonganum has established populations outside of its native range, but it is not believed to cause significant damage to ecological or agricultural systems. The species is most often encountered on vegetation in disturbed or edge forest habitat.

Petiole with two waist segments (petiole & postpetiole)
Propodeal spines of moderate length
Antennae 12-segmented Antennal club with three segments
Antennal scrobe present & relatively strong
Slope of mesosoma even & gradual
Antennal insertion surrounded by a distinct elevated ridge
Hairs long, fine and abundant
Shape of petiole node rounded Petiole with relatively long & thin peduncle

Chart 1. Tetramorium tonganum vs. T. bicarinatum, T. insolens, T. pacificum, T. lanuginosum
Chart 2. Tetramorium tonganum vs. T. simillimum, T. caldarium, Wasmannia auropunctata

	T. tonganum	T. bicarinatum	T. insolens	T. pacificum	T. lanuginosum
Head
Profile
Hairs	long & abundant	long & abundant	long & abundant	long & abundant	long & very dense
Propodeal spines	moderate	long	long	long	long
Petiole node shape		square	wave-shaped	wave-shaped	rounded
	T. tonganum	T. bicarinatum	T. insolens	T. pacificum	T. lanuginosum

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Chart 2. Tetramorium tonganum vs. T. simillimum, T. caldarium, Wasmannia auropunctata

	T. tonganum	T. simillimum	T. caldarium	W. auropunctata
Head
Profile
Total number of antennal segments	12	12	12	11
Antennal club segments	three	three	three	two
Propodeal spines	moderate	short	short	long
Hairs	long & abundant	short & sparse	short & sparse	long, thick & sparse
Petiole node shape	rounded	square	square	square
Petiole peduncle	thin	thick	thick	(not applicable)
	T. tonganum	T. simillimum	T. caldarium	W. auropunctata

• Antweb: specimen images, data & maps
  
  
• Bolton, B. (1977) The ant tribe Tetramoriini (Hymenoptera: Formicidae). The genus Tetramorium Mayr in the Oreintal and Indo-Australian regions, and in Australia. Bulletin of the British Museum (Natatural History) Entomology, 36, 67-151.
  
  
• 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, 1-10.