Taxonomic name: Tapinoma melanocephalum (Fabricius, 1793)
Synonyms: Formica familiaris Smith, F. 1860, Formica melanocephalum Fabricius, 1793, Formica nana Jerdon, Myrmica pellucida Smith, F. 1857, Tapinoma melanocephalum (Fabricius): Mayr, 1862, Tapinoma melanocephalum var. australe Santschi 1928, Tapinoma melanocephalum var. australis Santschi 1928
Common names: albaricoque, awate-konuka-ari, black-headed ant, ghost ant, hormiga bottegaria, house infesting ant, tiny yellow house ant, tramp ant
Organism type: insect
Tapinoma melanocephalum is known as a tramp ant as its spread around the globe has been assisted by human activities. It is highly flexible in the habitats it occupies, providing there is some form of disturbance allowing it to establish ahead of more dominant ant species, and it nests readily outdoors or indoors. Tapinoma melanocephalum is a household pest, as well as disturbing greenhouse environments and can transport pathogenic microbes in hospitals.
T. melanocephalum workers are extremely small, 1.3 to 1.9mm long and monomorphic. They have 12-segmented antennae with the segments gradually thickening towards the tip. The first segment of the antennal funiculus is longer than the second and third segments combined. Antennal scapes surpass the occipital border. They are distinctively bicoloured: the head (including antennae, except for first 2 segments) and sides of the alitrunk are blackish-brown. The gaster and legs are opaque or milky white giving this species its characteristic "ghost" appearance. The gaster has 4 segments on its upper surface and has a slit-like anal opening which is hairless. Eyes are large with each having 9 or 10 facets that span its long axis. The mandibles each have 3 large teeth and about 7 small denticles on them. Stingers are absent on T. melanocephalum. The small size, combined with the pale colour, make this species hard to see. When crushed, the workers emit an odor similar to that of rotten coconuts (Harris et al. 2005; Nickerson et al. 2003; and Onoyama and Terayama, 2003).
Please click on AntWeb: Tapinoma melanocephalum 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 comare: head, profile, dorsal, or label.
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 Tapinoma melanocephalum contains an overview, diagnostic features, comparision charts, images, nomenclature and links. (Sarnat, 2008)
Technomyrmex spp., Tapinoma sessile
agricultural areas, ruderal/disturbed, urban areas
T. melanocephalum is highly flexible in the habitats occupied, providing there is some form of disturbance allowing it to establish ahead of more dominant ant species. It nests readily outdoors or indoors. Generally, the colonies occupy local sites that are too small or unstable to support entire large colonies. The sites include tufts of dead but temporarily moist grass, plant stems, and cavities beneath detritus in open, rapidly changing habitats. Indoors, the ant colonizes wall void or spaces between cabinetry and baseboards. It will also nest in potted plants. Hölldobler and Wilson (1990) report that ghost ants are opportunistic nesters in places that sometimes remain habitable for only a few days or weeks Usually, nesting occurs in disturbed areas, in flowerpots, under objects on the ground, under loose bark, and at the bases of palm fronds. Indoors, the ant nests in small spaces such as cracks, spaces between books, or wall voids. Indoor foragers often come from outside. This is a very common pest inside homes (Harris et al. 2005; Nickerson et al. 2003).
T. melanocephalum is a household pest. It can not only invade houses from outside, but nest inside as well and will compromise food sources. It infests buildings in large numbers and has established in temperate locations. It has become established in heated greenhouses where it can become a problem, especially if it defends honeydew producing, plant pests against introduced biological control organisms. T. melanocephalum is capable of transporting pathogenic microbes in hospitals. Some people suffer a slight, red irritation of the skin following contact with this ant (Harris et al. 2005; Nickerson et al. 2003).
Under some conditions T. melanocephalum may be beneficial as a biocontrol agent. Studies show that the ant can be a significant predator of the important plant pest, the two-spotted spider mite (Tetranychus urticae) (Osborne et al., 1995). T. melanocephalum was also noted as being useful in orchid greenhouses in the Netherlands, as it controlled vermin (Stärcke, 1943 in Boer & Vierbergen, 2008).
Shepard & Gibson (1972) report that a symbiotic relationship has developed in Costa Rica between T. melanocephalum and jumping spiders (Araneae: Salticidae) which were found inhabiting the ants nests. It is believed that the spiders provided some protection to the ants from natural enemies and the nest served as a foundation for web construction (Osborne et al. 1995.)
Native range: It has not been established if this species is of African or Oriental origin (Nickerson et al. 2003).
Known introduced range: Australasia-Pacific, Europe, North America, and South America (Shattuck and Barnett, 2001; Landau et al. UNDATED; Nickerson et al. 2003; and Osborne et al. 1995).
Introduction pathways to new locations
Other: The dispersal of T. melanocephalum is human assisted. In urban environments colonies may occupy, and be transported on, a huge variety of household goods, e.g., laptops, potted plants, luggage, cut flowers, instrument-case lining, piles of clothing, and probably a wide variety of other goods. The main requirement for successful transfer is that the goods end up in a suitable heated environment (Harris et al. 2005).
Other: T. melanocephalum is so widely distributed by commerce that it is impossible to determine its original home (Smith 1965) (Nickerson et al. 2003).
Local dispersal methods
Natural dispersal (local): T. melanocephalum spreads from focal colonies by colony budding. Queens walk on foot accompanied by workers to a new nesting site (Harris et al. 2005).
Chemical: Ghost ant colonies are highly mobile and frequently move from overpopulated nests, making them difficult to eradicate. Contact insecticides can be used on colonies, but colonies may be composed of many nests, and killing workers is only a temporary solution. The best management technique is poison baits (Texas A&M University, 2008). Presto® (fipronil) and Xstinguish® (fipronil) have been highly effective at controlling certain ant species. These baits might also be attractive to T. melanocephalum because the target species have similar food preferences. Boric Acid is another alternative being investigated. The concentration of boric acid is too high in most available commercial baits but at low concentrations it has been shown to be extremely effective at killing laboratory colonies T. melanocephalum. Peanut butter and sweet solutions such as honey and sugar water are preferred attractrants of T. melanocephalum. There have been very few studies conducted which specifically consider control of T. melanocephalum (Texas A&M University, 2008).
T. melanocephalum foragers are opportunists. They forage on many household foods, especially sweet foods. They are fond of honeydew and tend honeydew-excreting insects in hot climates and glasshouses. This ant also feeds on dead and live insects and root scales. Foragers locate and recruit to food rapidly, and recruit in numbers, but are displaced easily when more dominate ant species recruit to the same food source in larger numbers (Harris et al. 2005; Nickerson et al. 2003).
T. melanocephalum spreads from focal colonies by colony budding. This occurs when one or more reproductive females, accompanied by several workers and possibly some brood (larvae and pupae) leave an established colony for a new nesting site. This method of dispersal aids spread of this species over relatively short distances and ensures they become dispersed throughout suitable habitat (Harris et al. 2005; Nickerson et al. 2003).
T. melanocephalum have polygynous, unicolonial, colonies that can build up large numbers, with individual nests containing 100-1000 individuals. Generally, the colonies occupy local sites that are too small or unstable to support entire large colonies so the colonies are broken into subunits that occupy different nest sites and exchange individuals back and forth along odor trails. There does not appear to be any fighting between members of different colonies or nests, at least when they originate from the same area. They often occupy temporary habitats (plant stems, clumps of dried grass, debris, under potted plants) and readily migrate if disturbed or conditions become unfavourable. Multiple queens may be spread out in multiple sub colonies. Queens have a very short lifespan of only a few weeks (Harris et al. 2005; Nickerson et al. 2003).
Compiled by: National Biological Information Infrastructure (NBII) & IUCN/SSC Invasive Species Specialist Group (ISSG)
Last Modified: Wednesday, 10 March 2010