Threat Level: Medium

Tetramorium bicarinatum is a medium-sized ant with a reddish head, mesosoma and waist contrasting with a dark gaster. 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 strong propodeal spines. Like all myrmicines, T. bicarinatum has two waist segments and a gaster armed with a stinger. In the field it can be recognized by its bicolored appearance, medium size and strong recruiting to baits and food resources. See the video for additional field identification clues.

There are five additional Tetramorium species that are spread across the Pacific Island region. Tetramorium bicarinatum can be distinguished from these by the combination of the following characters: (1) square-shaped petiolar node, (2) long propodeal spines, (3) abundant long thin pilosity, and (4) a reddish head, mesosoma and waist contrasting with a dark gaster. See the comparison chart for additional characters.

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 bicarinatum is believed to be native to Africa, but is now widely distributed across the Pacific and other tropical regions. The species can achieve dense populations in disturbed habitats and is likely to adversely affect native biodiversity.

Petiole with two waist segments (petiole & postpetiole)
Propodeal spines long
Antennae with 12 segments Antennal club with three segments
Antennal scrobe present
Slope of mesosoma even & gradual
Antennal insertion surrounded by a distinct elevated ridge
Shape of petiole node square
Hairs long and moderately abundant
Anterior margin of clypeus with notch present
Gaster darker than rest of body

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

	T. bicarinatum	T. insolens	T. pacificum	T. lanuginosum
Head
Profile
Hairs	long & abundant	long & abundant	long & abundant	long & very dense
Petiole node shape	square	wave-shaped	wave-shaped	rounded
Color	gaster darker than rest of body	pale	dark	gaster darker than rest of body
Anterior clypeal margin with notch	present	present	present	present
	T. bicarinatum	T. insolens	T. pacificum	T. lanuginosum

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Chart 2. Tetramorium bicarinatum vs. T. tonganum, T. simillimum, T. caldarium

	T. bicarinatum	T. tonganum	T. simillimum	T. caldarium
Head
Profile
Propodeal spines	long	moderate	short	short
Hairs	long & abundant	long & abundant	short & sparse	short & sparse
Petiole node shape	square	rounded	square	square
Anterior clypeal margin	present	absent	absent	absent
Size	moderate (> 3.5mm)	small (~ 2mm)	small (~ 2mm)	small (~ 2mm)
	T. bicarinatum	T. tonganum	T. simillimum	T. caldarium

• 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, 1-109.