Taxonomic name: Anoplolepis gracilipes (Fr. Smith)
Synonyms: Anoplolepis longipes Emery 1925, Formica longipes Jerdon 1851, Plagiolepis longipes Emery 1887
Common names: ashinaga-ki-ari (Japanese), crazy ant (English), Gelbe Spinnerameise (German), gramang ant (Indonesian Bahasa), long-legged ant (English), Maldive ant (English-Seychelles), yellow crazy ant (English)
Organism type: insect
Anoplolepis gracilipes (so called because of their frenetic movements) have invaded native ecosystems and caused environmental damage from Hawaii to the Seychelles and Zanzibar. On Christmas Island in the Indian Ocean, they have formed multi-queen supercolonies. They are also decimating the red land crab (Gecarcoidea natalis) populations. Crazy ants also prey on, or interfere in, the reproduction of a variety of arthropods, reptiles, birds and mammals on the forest floor and canopy. Their ability to farm and protect sap-sucking scale insects, which damage the forest canopy on Christmas Island, is one of their more surprising attributes. Although less than 5% of the rainforest on Christmas Island has been invaded so far, scientists are concerned that endangered birds such as the Abbott’s booby (Sula abbotti), which nests nowhere else in the world, could eventually be driven to extinction through habitat alteration and direct attack by the ants.
Anoplolepis gracilipes is one of the largest invasive ants and are typically small to medium-sized and range from 1-2mm, like Wasmannia auropunctata, to more than 5mm (Holway et al. 2002). The ant, also known as the long-legged ant, is notable for its remarkably long legs and antennae. A. gracilipes workers are monomorphic, displaying no physical differentiation (Holway et al. 2002). It has a yellow-brownish body colour, and is weakly sclerotized. Workers have a long slender gracile body, with the gaster usually darker than the head and thorax. It may subdue or kill invertebrate prey or small vertebrates by spraying formic acid.
Please click on AntWeb: Anoplolepis gracilipes for more images and assistance with identification. The AntWeb image comparison tool lets you compare images of ants at the subfamily, genus, species or specimen level. You may also specify which types of images you would like to compare: head, profile, dorsal, or label.
Please see PaDIL (Pests and Diseases Image Library) Species Content Page Ants: Yellow crazy ant for high quality diagnostic and overview images.
Please follow this link for a fully illustrated Lucid key to common invasive ants [Hymenoptera: Formicidae] of the Pacific Island region [requires the most recent version of Java installed]. The factsheet on Anoplolepis gracilipes contains an overview, diagnostic features, comparision charts, images, nomenclature and links. (Sarnat, 2008)
agricultural areas, coastland, natural forests, planted forests, range/grasslands, riparian zones, riverine forest/freshwater swamp forest, ruderal/disturbed, scrub/shrublands, urban areas, water courses
Anoplolepis gracilipes are known to be ready invaders of disturbed habitats such as urban areas, forest edges or agricultural fields (Ness and Bronstein, 2004). The ability of A. gracilipes to live in human dwellings or human-frequented areas has meant it has become a serious pest in many households and buildings (O’Dowd et al. 1999).
The yellow crazy ant has been known to successfully colonise a variety of agricultural systems, including cinnamon, citrus and coffee crops and coconut plantations (Haines and Haines 1978, Van Der Goot 1916, in Holway et al. 2002; O’Dowd et al. 1999) and on banana, rambutan, mango, durian, sugarcane and langsat (Jochen Drescher pers.comm May 2010) . In agricultural regions it is typically found nesting at the base, or even in the crown, of crop plants. For example, on New Guinea it nests in the crowns of coconut trees, feeding off honeydew-producing scale insects and palm flower nectar (Young 1996, in O’Dowd et al. 1999).
A. gracilipes is also capable of invading undisturbed habitats as in the case of the drier monsoon forests on Christmas Island (Indian Ocean), where the yellow crazy ant experienced a population explosion and thrives in (previously) undisturbed native forest habitats (CBD, 2003); it is however not known to enter lowland rainforest or submontane rainforest (Jochen Drescher pers.comm May 2010). The nesting requirements of the ant are general and it often nests under leaf litter or in cracks and crevices (Lewis et al. 1976, Rao and Veeresh 1991, in O’Dowd et al. 1999). On Christmas Island, the yellow crazy ant takes advantage of crab burrows, the woody debris of the forest floor, tree hollows and epiphytes and the hollows created at the base of palm leaves (O’Dowd et al. 1999).
High densities of the yellow crazy ant (Anoplolepis gracilipes) have the potential to devastate native 'keystone'
species, resulting in a rapid alteration of ecosystem processes and negative effects on
endemic species. The most notable example concerns the native forests of Christmas
Island, in which populations of the yellow crazy ant have exploded in recent decades (at
least 60 years after its initial introduction) (CBD 2003).
Please follow this link for more details on the impacts of yellow crazy ants on biodiversity.
For a summary of the general impacts of invasive ants, such as their affect on mutualistic relations, the competitive pressure they impose on native ants and the effect they may have on vulnerable ecosystems please read this document: invasive ants impacts compiled by the ISSG.
Native range: The yellow crazy ant (Anoplolepis gracilipes) remains poorly studied and even its native range is not certain. It may have originated from Africa or Asia (Holway et al. 2002). The centre of diversity for the genus is Africa and A. gracilipes is the only species distributed beyond that continent.
Known introduced range: It has been introduced into parts of Africa (including South Africa), Asia, South America (including Brazil) and Australia. It has been introduced onto some Caribbean islands, some Indian Ocean islands (including the Seychelles, Madagascar, Mauritius, La Réunion, the Cocos Islands and the Christmas Islands) and some Pacific islands (including New Caledonia, Hawai‘I, French Polynesia, Okinawa, Vanuatu, Micronesia and the Galapagos archipelago) (McGlynn 1999; Holway et al. 2002; Lewis et al. 1976, Haines and Haines 1978a, Veeresh and Gubbaiah 1984, in O’Dowd et al. 1999).
Introduction pathways to new locations
Agriculture: Anoplolepis gracilipes has been known to successfully colonise a variety of agricultural systems, including cinnamon, citrus and coffee crops and coconut plantations (Haines and Haines 1978, Van Der Goot 1916, in Holway et al. 2002; O’Dowd et al. 1999). Because of this the movement of produce or habitat material out of ant-invaded agricultural regions could potentially facilitate the long distance dispersal of the ant.
Agriculture: Translocated in soil, produce and timber.
Aircraft: Transported in packaging material, timber.
Military: Transported in road vehicles, machinery, boats, and aircraft.
Nursery trade: Transported in soil and produce.
Other: Deliberate introductions for biological control of plant pests on coconut, coffee and cacao plantations.
Road vehicles (long distance): Transported in soil, packaging materials, pallets.
Seafreight (container/bulk): Transported in goods, packaging, pallets in container. Anoplolepis gracilipes has entered Australian ports in sea cargo containers in Cairns and Brisbane, Queensland, Australia and been intercepted in Fremantle, Western Australia.
Local dispersal methods
Agriculture (local): Anoplolepis gracilipes has been known to successfully colonise a variety of agricultural systems, including cinnamon, citrus and coffee crops and coconut plantations (Haines and Haines 1978, Van Der Goot 1916, in Holway et al. 2002; O’Dowd et al. 1999). Because of this, agricultural activities are likely to aggravate the spread of the ants locally.
Boat: Translocated in packaging material, timber, produce, soil, plants.
Natural dispersal (local): Colonies rarely or never disperse via winged female reproductive forms, and instead rely on colony “budding” for colony dispersal. The rate of spread is lower that that of colonies able to disperse via flight. Species that reproduce and disperse solely by budding, depend to a greater extent on human-mediated dispersal instead of natural dispersal for the colonisation of distant locations. However, A. gracilipes spreads about 37 to 402 metres per year in the Seychelles, which is relatively high (Holway et al. 2002). On Christmas Island, an infestation of yellow crazy ants expanded 1100m in one year, according to one survey. This represents greater than a ten-fold increase in area and an average spread of about three metres per day (O’Dowd et al. 1999).
Natural dispersal (local): Colony budding.
Other (local): Redistribution for biological control on coconut, coffee, and cacao plantations.
Road vehicles: Translocated in packaging material, timber, produce, soil, plants.
Translocation of machinery/equipment (local): Movement of contaminated mining and agricultural equipment.
Preventative measures: The Pacific Ant Prevention Programme is a proposal prepared for the Pacific Plant Protection Organisation and Regional Technical Meeting for Plant Protection. This plan aims to prevent the red imported fire ant and other invasive ant species from establishing within or spreading between countries in the Pacific.
A detailed pest risk assessment for the eight species ranked as having the highest potential risk to New Zealand was prepared as part of 'The Invasive Ant Risk Assessment Project',
Harris et al. 2005., for Biosecurity New Zealand by Landcare Research. Anoplolepis gracilipes scored as a high-risk threat to New Zealand. The Invasive ant risk assessment for A. gracilipes can be viewed at Anoplolepis gracilipes risk assessment. Please see Anoplolepis gracilipes information sheet for more information on biology, distribution, pest status and control technologies.
Chemical: The toxic principles in ant baits include the so-called “stomach” poisons, hydramethylnon (Maxforce, Amdro), sulfuramid and sodium tetraborate decahydrate (Borax). Insect Growth Regulators (IGRs) disrupt development and include compounds such as methoprene and fenoxycarb. Stomach poisons work relatively fast compared to IGRs, but may sometimes work too quickly, eliminating workers before the insecticide can be distributed throughout the entire colony. One promising approach is to use pheromones (compounds produced by a species that regulate their own behaviour) as “biopesticides” to disrupt the reproduction by the queen (O’Dowd et al. 1999). Baits should be designed with the foraging strategies of the specific ant species in mind. Determining the preferred size, type and dispersal pattern of the bait is an important step. Nesting, foraging and behavioural traits of the ant should all be taken into consideration. The use of appropriately designed baits is needed to reduce the cost of toxin use to native ant populations and non-target fauna (McGlynn, 1999).
Please follow this link for more detailed information on the management of the yellow crazy ant compiled by the ISSG.
Anoplolepis gracilipes have a broad diet characteristic of many invasive ants. A generalised feeding regime increases the invasiveness of an ant due to the increased ability to gain nutrition from available resources including grains, seeds, arthropods, decaying matter and vegetation (Holway et al. 2002; Ness and Bronstein 2004). The yellow crazy ant is a scavenger and preys on a variety of litter and canopy invertebrates, such as small isopods, myriapods, molluscs, arachnids, land crabs and insects (O’Dowd et al. 1999). In the Seychelles, they feed on invertebrates and will attack, kill, and dismember large arthropods (Haines et al. 1994, in O’Dowd et al. 1999). Like all ants, they require proteinaceous foods for brood production (O’Dowd et al. 1999).
In addition to protein-rich foods A. gracilipes may rely heavily on carbohydrate-rich nutrient sources, such as plant nectar or honeydew-producing scale insects (especially insects in the Homoptera genus). In the Seychelles, the quantity of honeydew in a 2.5mg worker is estimated to be up to 50% (Haines et al. 1994 in O’Dowd et al. 1999). The presence of Homoptera insects may be so important that it may limit population growth. For example, in cocoa plantations in Papua New Guinea Homoptera insect populations are thought to be necessary to support and sustain A. gracilipes colonies (Holway et al. 2002).
Anoplolepis gracilipes colonies are polygynous. Worker production fluctuates but is continuous throughout the year. Sexual offspring may occur year-round, but are generally produced seasonally (prior to the rainy season) (Baker 1976, in O’Dowd et al. 1999). Colony budding is an important form of dispersal for the ant, although winged queens and males (known as alates) have been reported on Christmas Island. It is unclear if winged-forms of the ant are able to start new colonies.
The life cycle of Anoplolepis gracilipes has been estimated to take 76-84 days. Eggs hatch in 18-20 days, and worker larvae develop in 16-20 days. Pupae of workers require around 20 days to develop while those of queens develop in 30-34 days.
This species has been nominated as among 100 of the "World's Worst" invaders
Compiled by: Dr. Dennis O'Dowd, Centre for Analysis and Management of Biological Invasions, Australia & IUCN/SSC Invasive Species Specialist Group (ISSG)
Last Modified: Monday, 28 September 2009