This is a relatively large, yellow / orange ant that is about 4-5 mm in length. The abdomen is usually a uniform light yellow but sometimes has dark brown markings. Their legs and antennae appear very long in comparison with the body and they can move very fast. They do not have a sting, but can spray formic acid which they use to subdue prey and to act as a defense mechanism. Queens are much larger than the workers, averaging about 10 mm in length.
The yellow crazy ant’s natural habitat is not known, but it has been speculated that the species originated in East Africa. Because the ants will create nests in many different places, they are able to disperse via trucks, boats and other forms of human transport. Because of this it has been introduced into a wide range of tropical and subtropical environments where it has naturalized and spread.
They are opportunistic species and will nest under wood and stones, in other animals abandoned burrows, under dead bark on trees, in crevices between bricks and even just under dead leaves lying on the ground. In captivity they seem to be quite happy in most types of artificial nest.
A. gracilipes has been described as a ‘scavenging predator’ and has a broad diet, a characteristic of many successful invasive species. It consumes a wide variety of foods, including grains, seeds, arthropods and decaying matter, including vertebrate corpses. They will also attack and dismember slow moving invertebrates such as small isopods, arachnids, earthworms and insects.
Like all ants they require a protein-rich food source for the queen to lay eggs and carbohydrates as energy for the workers. They get their carbohydrates from plant nectar and honeydew producing insects, especially scale insects and aphis. These are plant pests that feed on sap of trees and release honeydew, a sugary liquid. Ants eat the honeydew, and in return protect the scale from their enemies and spread them among trees, an example of mutual cooperation.
Newly mated queens will frequently re-enter their original nest boosting the potential for population growth and when conditions are favorable, they will very quickly form vast super colonies. This species naturally spreads and colonizes new areas through ‘budding’ - when mated queens and workers leave the mother nest to establish a new one. Generally, colonies that disperse this way have a lower rate of dispersal and need human intervention to reach distant areas, however in this species the newly mated queens are also capable of independent colony foundation. In the Seychelles it has been recorded that established colonies of A. gracilipes will increase their range as much as 400 m a year. A survey on Christmas Island yielded an average spreading speed of three meters a day, the equivalent of one kilometer a year.
This is a species that easily becomes established and dominant in new habitat due to traits such as its aggression toward other ant species, little aggression toward members of its own species, efficient fast recruitment, ability to utilize a wide range of food sources and large colony size. Rather than establishing several competitive nests with individual queens (as majority of other ant species do), yellow crazy ants establish super colonies consisting of large interconnected nests containing multiple queens. By cooperating, they can successfully outnumber and displace other species, thereby dominating food and nesting resources.
Summary: They are a good sized attractively colored ant, easy to keep and will adapt to most types of artificial nest. They can have multiple queens in a colony, will take a wide range of food and breed quickly.