Threat Level: low

Tetramorium lanuginosum is a small ant with a reddish head, mesosoma and waist contrasting with a dark gaster, and a dense pelt of long white pilosity. 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. lanuginosum has two waist segments and a gaster armed with a stinger. See the video for additional field identification clues.

There are five additional Tetramorium species that are spread across the Pacific Island region. Tetramorium lanuginosum can be distinguished from these by the combination of the following characters: (1) a rounded petiolar node, (2) long propodeal spines, (3) extremely dense 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 lanuginosum (formerly known as Trigliphothrix striatidens) is widely distributed across the Pacific and other tropical regions. It is most often encountered in forest leaf litter. The species is not known to cause significant damage to ecological or agricultural systems.

Petiole with two waist segments (petiole & postpetiole)
Propodeal spines long
Antennae 12-segmented 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 evenly rounded
Hairs long, bifurcated & densely distributed
Anterior margin of clypeus with notch present
Gaster darker than rest of body

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

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

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

	T. lanuginosum	T. tonganum	T. simillimum	T. caldarium
Head
Profile
Propodeal spines	long	moderate	short	short
Hairs	long & very dense	long & abundant	short & sparse	short & sparse
Petiole node shape	rounded	rounded	square	square
Anterior clypeal margin	present	absent	absent	absent
	T. lanuginosum	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.