''Formica fusca'' is a black-colored

ant Ants are Eusociality, eusocial insects of the Family (biology), family Formicidae and, along with the related wasps and bees, belong to the Taxonomy (biology), order Hymenoptera. Ants evolved from Vespoidea, vespoid wasp ancestors in the Cre ...

commonly found throughout Europe as well as parts of southern Asia and Africa. It has the common names silky ant or dusky ant. The range within the

palaearctic The Palearctic or Palaearctic is a biogeographic realm of the Earth, the largest of eight. Confined almost entirely to the Eastern Hemisphere, it stretches across Europe and Asia, north of the foothills of the Himalayas, and North Africa. Th ...

region extends from Portugal in the west to Japan in the east and from Italy in the south to

Fennoscandia __NOTOC__ Fennoscandia (Finnish language, Finnish, Swedish language, Swedish and ; ), or the Fennoscandian Peninsula, is a peninsula in Europe which includes the Scandinavian Peninsula, Scandinavian and Kola Peninsula, Kola peninsulas, mainland ...

in the north. Populations from North America have been split off as a separate species, '' Formica subaenescens''. ''F. fusca'' nests are usually found in rotten tree stumps or under stones in clearcut areas and along woodland borders and hedgerows. The species also often occurs in urban areas, feeding on honeydew secreted by the

aphids Aphids are small sap-sucking insects in the Taxonomic rank, family Aphididae. Common names include greenfly and blackfly, although individuals within a species can vary widely in color. The group includes the fluffy white Eriosomatinae, woolly ...

found on weeds.

Eusociality

Colonies A colony is a territory subject to a form of foreign rule, which rules the territory and its indigenous peoples separated from the foreign rulers, the colonizer, and their '' metropole'' (or "mother country"). This separated rule was often or ...

are facultatively

polygynous Polygyny () is a form of polygamy entailing the marriage of a man to several women. The term polygyny is from Neoclassical Greek πολυγυνία (); . Incidence Polygyny is more widespread in Africa than in any other continent. Some scholar ...

(though weakly so, with a mean number of queen of 3.09); though the queens coexist amicably, contribution to the brood tends to be unequal. Nests are usually small, containing 500–2,000 workers. The workers are large, at long, and fast moving, though timid. To ensure that non-nest mate eggs are not reared, these workers will engage in a process known as

worker policing Worker policing is a behavior seen in colonies of social hymenopterans (ants, bees, and wasps) whereby worker females eat or remove eggs that have been laid by other workers rather than those laid by a queen. Worker policing ensures that the of ...

. Alate (winged) forms are produced in June/July and

nuptial flight Nuptial flight is an important phase in the reproduction of most ant, termite, and some bee species. It is also observed in some fly species, such as '' Rhamphomyia longicauda''. During the flight, virgin queens mate with males and then land ...

s are in July/August. A study has found evidence of

nepotism Nepotism is the act of granting an In-group favoritism, advantage, privilege, or position to Kinship, relatives in an occupation or field. These fields can include business, politics, academia, entertainment, sports, religion or health care. In ...

in ''F. fusca'', in contrast with previous experiments with other ant species; this conclusion has been challenged on the grounds that the observed pattern may result from differences in egg viability.

Ecology

''F. fusca'' feeds on small insects such as codling moth larvae,

aphid Aphids are small sap-sucking insects in the Taxonomic rank, family Aphididae. Common names include greenfly and blackfly, although individuals within a species can vary widely in color. The group includes the fluffy white Eriosomatinae, woolly ...

honeydew and

extrafloral nectaries Nectar is a viscous, sugar-rich liquid produced by plants in glands called nectaries, either within the flowers with which it attracts pollinating animals, or by extrafloral nectaries, which provide a nutrient source to animal mutualists, ...

. Workers have been found to have a very high resistance to some pathogens and it is thought this may be due to ''F. fusca'' utilising the antibiotic properties of their formic acid, additional to the use of their

metapleural gland Metapleural glands (also called metasternal or metathoracic glands) are secretory glands that were considered unique to ants and basal in the evolutionary history of ants. They are responsible for the production of an antibiotic fluid that then col ...

. The larvae of '' Microdon megalogaster'', a member of the ant fly genus, have been observed in the nests of these ants. The

inquiline In zoology, an inquiline (from Latin ''inquilinus'', "lodger" or "tenant") is an animal that lives commensally in the nest, burrow, or dwelling place of an animal of another species. For example, some organisms, such as insects, may live in the ...

relationship of these fly larvae is not well understood.

Behaviour

Learning abilities

Workers of this ant species can learn to associate an olfactory stimulus to a reward (sugar solution) during a

classical conditioning Classical conditioning (also respondent conditioning and Pavlovian conditioning) is a behavioral procedure in which a biologically potent Stimulus (physiology), stimulus (e.g. food, a puff of air on the eye, a potential rival) is paired with a n ...

protocol. The learning abilities of this species were tested using single compounds found in flower emission. Ants are fast to learn, and only a single presentation of the stimulus is enough for them to form a genuine

long-term memory Long-term memory (LTM) is the stage of the Atkinson–Shiffrin memory model in which informative knowledge is held indefinitely. It is defined in contrast to sensory memory, the initial stage, and short-term or working memory, the second stage ...

. This formed memory is also resistant to

extinction Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

Detection of human cancer cells

Ants of this species can also detect

volatile organic compound Volatile organic compounds (VOCs) are organic compounds that have a high vapor pressure at room temperature. They are common and exist in a variety of settings and products, not limited to Indoor mold, house mold, Upholstery, upholstered furnitur ...

s emitted by

cancer Cancer is a group of diseases involving Cell growth#Disorders, abnormal cell growth with the potential to Invasion (cancer), invade or Metastasis, spread to other parts of the body. These contrast with benign tumors, which do not spread. Po ...

cells. After a 3-trial conditioning, they can differentiate cancer cell lines (

MCF-7 MCF-7 is a breast cancer cell line isolated in 1970 from a 69-year-old woman. MCF-7 is the acronym of Michigan Cancer Foundation-7, referring to the institute in Detroit where the cell line was established in 1973 by Herbert Soule and co-workers ...

) from healthy ones (MCF-10A). They can also discriminate one cell line (

) from another cancerous one ( MDA-MD-231).

Detection of human tumours

Later on, these learning abilities were tested using urine from tumour-bearing mice. Mice were grafted with human breast tumours, and the urine was collected and used as a source of odour for learning. Different mice were used between the training and the tests to forbid ants from using individual cues emitted by the mice. In that way, ants had to focus on the presence/absence of tumour, and not on one specific individual odour. Ants were able to detect the presence of human tumours in the urine of the mice, and to discriminate sick individuals from healthy ones.