Threat Level: High

Paratrechina longicornis, commonly known as the Black Crazy Ant or the Long-horn Ant, is a relatively small, dark colored species with extraordinarily long appendages, rows of long thick white hairs, and bulging eyes that break the outline of the head. Its gaster, like all formicines, is armed with an acidopore. In the field it can often be recognized by the rapid and erratic movement for which it is called a "crazy" ant (see video). It recruits strongly to baits and food resources with long foraging lines. The extraordinary length of the antennal scapes, pilosity, dark color, small size and foraging behavior make this a relatively easy ant to identify in the field.

Anoplolepis gracilipes is the only other ant included in PIAkey with antennal scapes greater than 1.5 times the length of the head. Although A. gracilipes also has bulging eyes and an acidopore, it is larger in size, paler in color and lacks the distinct pilosity of P. longicornis.

The remaining two Paratrechina included in PIAkey have shorter antennal scapes, eyes that lie within the outline of the head, and darker erect pilosity.

For a more complete review of the biology, impacts and management of P. longicornis, users are referred to the IUCN/SSC Invasive Species Specialist Group (ISSG) web page.

Wilson and Taylor (1967) offer the following discussion of Paratrechina longicornis:

P. longicornis is one of the most widespread and abundant of all pantropical species. It is especially well adapted to dry habitats and abounds in the most urbanized portions of many tropical towns and cities. It probably originated within the Old World tropics, perhaps specifically in southeastern Asia or Melanesia.

Paratrechina is a diverse genus with many taxonomically difficult species that occur in the Pacific region. If a specimen does not match the description or images of species included in PIAkey, it is very possible that it is either a native species or a different introduced species.

Waist with one segment (petiole) Petiole raised, not flattened Petiole can be obscured by gaster
Gaster armed with acidopore
Long, white, thick hairs produced in pairs on body
Long, white, thick hairs produced in pairs on head
Eyes break outline of head
Antennal scape length greater than 1.5 times head length

	P. longicornis	P. bourbonica	P. vaga
Head
Profile
Antennal scape length relative to head length	~ 1.5x length of head	< 1.5x length of head	< 1.5x length of head
Eyes break outline of face	yes	no	no
Hairs on mesopleuron	sparse (usually < 20)	abundant (usually > 20)	sparse (usually < 20)
Color of hairs	white	dark	dark
	P. longicornis	P. bourbonica	P. vaga

• Antweb: specimen images, data & maps
  
  
• Global Invasive Species Database: information about ecology, distribution, impacts, management, references, links and contacts
  
  
• 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.