Long-legged ant, Maldive ant
The yellow crazy ant (Anoplolepis gracilipes), also known as the long-legged ant or Maldive ant, is a species of ant, thought to be native to West Africa or Asia. They have been accidentally introduced to numerous places in the world's tropics.
The yellow crazy ant has colloquially been given the modifier "crazy" on account of the ant's erratic movements when disturbed. Its long legs and antennae make it one of the largest invasive ant species in the world.
Like several other invasive ants, such as the red imported fire ant (Solenopsis invicta), the big-headed ant (Pheidole megacephala), the little fire ant (Wasmannia auropunctata), and the Argentine ant (Linepithema humile), the yellow crazy ant is a "tramp ant", a species that easily becomes established and dominant in new habitat due to traits such as aggression toward other ant species, little aggression toward members of its own species, efficient recruitment, and large colony size.
It is on a list of "one hundred of the world's worst invasive species" formulated by the International Union for Conservation of Nature (IUCN), having invaded ecosystems from Hawaii to the Seychelles, and formed supercolonies on Christmas Island in the Indian Ocean.
In 2023, a scientific article postulated a unique reproductive cycle for A. gracilipes, suggesting that males are obligate chimeras.
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DiurnalDiurnal animals are active during the daytime, with a period of sleeping or other inactivity at night. The timing of activity by an animal depends ...
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TerrestrialTerrestrial animals are animals that live predominantly or entirely on land (e.g., cats, ants, snails), as compared with aquatic animals, which liv...
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OviparousOviparous animals are female animals that lay their eggs, with little or no other embryonic development within the mother. This is the reproductive...
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starts withAnoplolepis gracilipes is a relatively large, yellow to orange 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 for which it can be mistaken. 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, while 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.
Several species of invasive ants belonging to the genera Camponotus and Paratrechina can appear similar to A. gracilipes. 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 waists.
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. Although widespread across the Pacific, A. gracilipes can cause significant damage to native biological diversity. Strong quarantine measures are encouraged to keep it from spreading to new localities.
The yellow crazy ant's natural habitats are the moist tropical lowlands of Southeast Asia, and surrounding areas and islands in the Indian and Pacific Oceans. It has been introduced into a wide range of tropical and subtropical environments including northern Australia, some of the Caribbean islands, some Indian Ocean islands (Seychelles, Madagascar, Mauritius, Réunion, the Cocos Islands and the Christmas Islands) and some Pacific islands (New Caledonia, Hawaii, French Polynesia, Okinawa, Vanuatu, Micronesia, Johnston Atoll, and the Galapagos archipelago). The species has been known to occupy such agricultural systems as cinnamon, citrus, coffee and coconut plantations. Because yellow crazy ants have generalized nesting habits, they are able to disperse via trucks, boats and other forms of human transport.
Crazy ant colonies naturally disperse through "budding", i.e. when mated queens and workers leave the nest to establish a new one, and only rarely through flight via female winged reproductive forms. Generally, colonies that disperse through budding have a lower rate of dispersal, requiring human intervention to reach distant areas. It has been recorded that A. gracilipes moves as much as 400 m (1,300 ft) a year in the Seychelles. A survey on Christmas Island, however, yielded an average spreading speed of 3 meters (9.8 ft) per day, the equivalent of one kilometer (0.6 mile) per year.
A gracilipes has been described as a "scavenging predator" exhibiting a broad diet, a characteristic of many invasive species. It consumes a wide variety of foods, including grains, seeds, arthropods, and decaying matter such as vertebrate corpses. They have been reported to attack and dismember invertebrates such as small isopods, myriapods, molluscs, arachnids, land crabs, earthworms and insects.
Like all ants, A gracilipes requires 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, aphids, and other Sternorrhyncha. Studies indicate that crazy ants rely so much on scale insects that a scarcity of them can actually limit ant population growth.
Similar to other ants, the queen produces eggs which are fertilized by male sperm that are stored in sperm stores. When an egg is fertilized, there are three distinct events that can happen: (i) the resulting diploid organism develops into a queen if the egg is fertilized by an R sperm or (ii) into an infertile diploid worker if the egg is fertilized by a W sperm. However, a third outcome has been described in a 2023 scientific study: (iii) the egg is fertilized by a W sperm but the parental nuclei bypasses the fusion of the two gametes and divide separately within the same egg, leading to a haploid male that is chimeric with a portion of cells carrying the W genome and a portion of cells carrying the R genome. Interestingly, not all tissues have equal proportions of each cell line, with sperm cells mostly carrying the W genome and thus providing the W alleles with a fitness advantage. This is the first known case of obligate chimerism in animals.
