Taxonomic name: Monomorium pharaonis (Linnaeus, 1758)
Synonyms: Atta minuta Jerdon , Diplorhoptrum domesticum (Shuckard) , Formica antiguensis Fabricius , Formica pharaonis Linnaeus , Monomorium domestica (Shuckard) , Monomorium pharaonis (Linnaeus) , Monomorium vastator (Smith) , Myrmica (Monomorium) contigua Smith , Myrmica (Monomorium) fragilis Smith , Myrmica (Monomorium) vastator Smith , Myrmica (Myrmecina) domestica Shuckard , Myrmica contigua Smith , Myrmica domestica Shuckard , Myrmica fragilis Smith , Myrmica pharaonis (Linnaeus) , Myrmica unifasciata Bostock , Myrmica vastator Smith
Common names: fourmi pharaon (French), pharaoh ant (English)
Organism type: insect
Monomorium pharaonis (the pharaoh ant) is native to Africa and has successfully invaded areas on every continent except Antarctica. It is concentrated in tropical regions but is also commonly found in temperate zones within suitable human infrastructure, especially buildings associated with the distribution or storage of food. Due to Monomorium pharaonis' ability to act as a vector for some bacterial human pathogens, its presence in hospitals is of great concern as it may increase infection rates.
Workers of the pharaoh ants (Monomorium pharaonis) are approximately 2mm in length and have body colours ranging from light-brown to red. The males are the same size as the workers but are black in colour. The queens are 4mm in length and slightly darker than the workers (Nickerson and Harris 2003).
Please click on AntWeb: Monomorium pharaonis 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: Pharaoh ant for high quality diagnostic and overview images.
Please follow this link for the information sheet on Monomorium pharaonis prepared as part of 'The invasive ant risk assessment project', Harris et al. 2005., for Biosecurity New Zealand by Landcare Research.
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 Monomorium pharaonis contains an overview, diagnostic features, comparision charts, images, nomenclature and links. (Sarnat, 2008)
ruderal/disturbed, urban areas
Many introduced ants, including Monomorium spp., are restricted to a tropical or subtropical climates. The pharaoh ant (Monomorium pharaonis) is not known to invade regions with cold climates although it may be associated with human infrastructure, including climate-controlled buildings. Although its abundance in cold climates will be restricted, its continued presence represents a potential to spread to locations more suitable for ant colonisation (McGlynn 1999; Holway et al. 2002).
Nests are rarely found outdoors but can be found almost anywhere indoors (including light sockets, potted plants and wall cracks or crevices). They typically nest close to sources of warmth and water and many investigators have noted this tendency (Mallis 1969, in Ebeling 1996).
The effect of climatic and temperature variables on ant abundance have been suggested as important when planning eradication programmes in cold to temperate regions. In laboratory conditions the time needed to eradicate pharaoh ant populations depended on the temperature; at 26°C eradication took 3 weeks; at 8°C an eradication could take only 30 minutes (Berndt 1980). Temperatures near 0°C lead to the eradication of large colonies within 6 days, which lead the author to the suggestion that the cold temperatures of the European winter could be exploited for aiding eradications of the pharaoh ant.
The pharaoh ant (Monomorium pharaonis) is classified as a “generalised Myrmicine” because it has generalised food and nesting requirements and defends resources if they are close to the nest (McGlynn 1999). In addition, M. pharaonis is known as a “tramp” species, which means it is particularly reliant on human-mediated dispersal and has a close association with humans. It frequently nests inside human structures but rarely displaces native species outside urban environments (McGlynn 1999; Holway et al. 2002).
M. pharaonis is a pest in many populated areas of the world. When it nests in homes, grocery stores or restaurants (which it often does) it often becomes a public nuisance. For example, in the Pacific Northwest it is a nuisance particularly in warehouses, grocery stores and other areas where food is kept (Antonelli and Akre 2003). Its presence in hospitals in of particular concern as it is a vector for the transmission of certain human bacterial pathogens (including Streptococcus pyogenes, Pseudomonas aeruginosa and Staphylococcus epidermidis), which commonly infect hospitalised patients (Nickerson and Harris 2003).
Please read Invasive ants impacts 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.
Apparently the name "pharaoh ant" originated from Linnaeus' mistaken impression that these ants were one of the biblical plagues during the time of Egyptian pharoahs (Riley 1889, in Ebeling 1996).
Native range: The pharaoh ant (Monomorium pharaonis) is native to West Africa.
Introduced range: It has been introduced into Asia (including Japan, India and Saudi Arabia), Australia, Europe, and North, Central and South America. It has been introduced onto some islands in the Indian Ocean (including Madagascar) and the Pacific Ocean (including New Zealand and some islands in the Hawaiian and Galapagos archipelagoes) (McGlynn 1999).
Introduction pathways to new locations
Seafreight (container/bulk): Commercial trade (transport of potted plants) has been implicated in the spread of M. pharaonis.
Local dispersal methods
Natural dispersal (local): M. pharaonis colonies spread via 'budding.'
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 with economic, environmental or social impacts from establishing within or spreading between countries in the Pacific.
Chemical: In general, ant baits that contain a metabolic inhibitor as the active ingredient (for example hydramethylnon or sulfluramid) have a 2 to 3 day delay before significant mortality occurs, while baits that contain an insect growth regulator (for example methoprene, fenoxycarb or pyriproxyfen) have a delay of several weeks. The latter (IGRs) provide gradual long-term control, while metabolic inhibitors provide short-term, localised and rapid control. As the colonies of pharaoh ant are usually composed of several nest sites a bait containing a metabolic inhibitor (or another fast-acting toxin) may need to be placed at a greater number of sites over a wider area to compensate for the relatively low level of natural toxin spread between the workers (Oi Vail and Williams 2000).
Please follow this link for more detailed information on the management of the Argentine ant Linepithema humile compiled by the ISSG.
Pharaoh ants (Monomorium pharaonis) are primarily nocturnal, feeding on a variety of foods, including fats, proteins, carbohydrates and small insects. Pharaoh ants will recruit to a number of household foods, including sweets, honey, cakes, greasy foods (such as butter) and fatty foods (such as meats) (Antonelli and Akre 2003).
In laboratory trials Haack and colleagues (1995) investigated the comparative recruitment to and distribution (among workers and larvae) of protein, lipid and carbohydrate. The results were as follows:
A) Recruitment: Liquid carbohydrate was recruited too quickly, while solid carbohydrate (table sugar) was not actively recruited. Corn starch was ignored by foraging workers. Workers actively recruited to sucrose solution and solid protein (moist egg yolk powder) foods after two days of starvation, but a seven day period of starvation was necessary for active recruitment to lipids such as peanut oil (indicating that lipids may not be rapidly depleted in the metabolism of the pharaoh ant).
B) Distribution: Peanut oil and sucrose solution baits were rapidly distributed among adult workers. Peanut oil was distributed rapidly to all larval stages, while the sucrose solution and solid protein baits were distributed primarily to older larvae.
A queen can lay up to 400 eggs in her lifetime and produces about 10 to 12 eggs per reproductive event. Larval instar development is cyclical at the colony level, suggesting reproductive bursts followed by lower reproductive activity of the queens (Alvares et al. 1993). The species is highly polygynous and workers are sterile. Unlike many ant species, M. pharaonis does not need to leave the nest to mate.
A study by Alvares and colleagues (1993) found that total egg to adult development period of the pharaoh ant (Monomorium pharaonis) ranged from 25 days to 54 days (greater than the respective minimum and maximum lengths reported in European populations). Eggs hatch within a week, and the larval period lasts up to 19 days. Queens live for about 12 months and non-sterile males die about 4 weeks after mating. A colony can have a population of several hundred thousand. When overcrowding becomes a problem a queen may take a few workers and immature ants and build a new nest, a mechanism known as budding or colony fission.
Compiled by: IUCN SSC Invasive Species Specialist Group
Updates with support from the Overseas Territories Environmental Programme (OTEP) project XOT603, a joint project with the Cayman Islands Government - Department of Environment
Last Modified: Monday, 4 October 2010