Threat Level: Medium

Anoplolepis gracilipes, known most commonly as the Yellow Crazy Ant (YCA), is a relatively large, yellow to orange colored ant with long legs, large eyes and extremely long antennal scapes.

Although A. gracilipes is the only invasive species in the genus Anoplolepis, there are several other genera that it can be mistaken for. Both Leptomyrmex and Oecophylla, can be confused with Anoplolepis because of their similar sizes and very long limbs. Anoplolepis can be distinguished from Leptomyrmex by the presence of an acidopore. Anoplolepis can be distinguished from Oecophylla by the more compact petiole Although both of these genera occur in the Pacific, neither contain any invasive species and are not treated in the PIAkey. Images of all three genera can be compared at Antweb.

Several species of invasive ants belonging to the genera Camponotus and Paratrechina can appear similar to A. gracilipes, and characters used to distinguish them are illustrated in the PIAkey and the comparison charts. Although several invasive species of Pheidole can also be slender bodied with long legs and long antennal scapes, they can be separated from A. gracilipes by their two-segmented waist.

Considered by the IUCN/SSC Invasive Species Specialist Group (ISSG) to be among the 100 worst invasive species in the world, A. gracilipes is widespread across the tropics, and populations are especially dense in the Pacific region. The species is most infamous for causing the "ecological meltdown" of Christmas Island (O'Dowd et al. 2003). Although widespread across the Pacific, Anoplolepis gracilipes can cause significant damage to native biological diversity, and strong quarantine measures are encouraged to keep it from spreading to new localities.

Large size, ~5mm Yellow to orange coloration Slender body long appendages Long neck connecting its body and head
One waist segment (the petiole) Petiole raised, not flat
Gaster armed with acidopore
Antennal scape length greater than 1.5 times head length
Large eyes that break outline of face

	A. gracilipes	C. maculatus group (minor worker)	P. longicornis
Face
Profile
Antennal scapes	~ 2x length of head	< 1.5x length of head	~ 1.5x length of head
Erect hairs	few, thin & not produced in pairs	many, thin & not produced in pairs	many, thick & produced in pairs
Mesosoma	impressed	not impressed	impressed
Size	large (~5mm)	large (~ 5mm)	small (~ 2.5mm)
Color	pale	pale	dark
	A. gracilipes	C. maculatus group (minor worker)	P. longicornis

• Antweb: specimen images, data & maps
  
  
• Global Invasive Species Database: information about ecology, distribution, impacts, management, references, links and contacts
  
  
• Abbott, K.L. (2005) Supercolonies of the invasive yellow crazy ant, Anoplolepis gracilipes, on an oceanic island: Forager activity patterns, density and biomass. Insectes Sociaux, 52, 266-273.
  
  
• O'Dowd, D.J., Green, P.T. & Lake, P.S. (2003) Invasional 'meltdown' on an oceanic island. Ecology Letters, 6, 812-817.