Formica
Formica obscuripes mound
Scientific classification
Kingdom: Animalia Phylum: Arthropoda Class: Insecta Order: Hymenoptera Family: Formicidae Subfamily: Formicinae Tribe: Formicini Genus: Formica Linnaeus, 1758
Diversity
c. 200
Species
Formica aquilonia Formica cunicularia Formica exsecta Formica exsectoides Formica fusca Formica lugubris Formica polyctena Formica pratensis Formica rufa Formica rufibarbis Formica sanguinea  many more, see text

Formica is a genus of ants. Species of the Forelian formica group, whose type is the red or southern wood ant Formica rufa, and are generally referred to as the wood ants. Many of the better known species have common names that usually include the words "wood ant", although F.rufa is also known as the "horse ant". The most common species in any particular area is likely to be referred to locally simply as the "wood ant". As their name implies, some tend to live in wooded areas where there exists no shortage of material with which they can thatch their mounds. However, sunlight is most important to Formica species, and colonies rarely survive for any considerable period in deeply shaded, dense woodland. The most shade tolerant species is F. lugubris.

A worker ant in the genus Formica

Mound building forest dwelling Formica like F. rufa often have considerable effect on their environment. They maintain large populations of aphids who's secretions they feed off of and defend from other predators. They also prey on other insects. In fact in many countries they are introduced in forests to control tree pests such as swains jack pine sawfly and eastern tent caterpillars in North America.

However Formica are found in a wide range of habitats from cities to seasides to grasslands to swamps to forests. Their nests are of many different types from simple craters to large mounds, under stones or logs, even in stumps. The Formica are a Nearctic genus. They are one of the more commonly seen ants in northern North America, along with Camponotus.

There are many species of Formica (ITIS records nearly 200). Some species, including Formica rufa, which is common in Southern England, make large visible nests of dry plant stems, leaves, or pine needles, usually based around a rotting stump. Wood ants typically secrete formic acid; F. rufa can squirt the acid from its acidopore several feet if alarmed. They can be relatively large: F. rufa workers can reach a maximum length of around 10 mm.

Formica are notable for their parasitic and slave making behaviors. There are three categories.

In the exsecta and microgyna groups virgin queens cannot start colonies on their own, but invade colonies of other groups and by various processes eventually oust the host queen and have the host workers help them raise their own brood. Eventually the colony consists of only the invading queen's offspring. This is called social parasitism.

In the sanguina group colonies are started as above, but then in some species of the group workers go out and raid colonies of other groups for new workers to act as slaves. Some species of this group need to do this to survive, for others it is optional.

The pallidefulva, neogagates, and fusca groups are the groups often enslaved and parasitized by the above groups. They are also enslaved by ants of the genus Polyergus. The rufa group is also suspected of social parasitism. The evolution of this behavior is yet unknown.

Species

• Formica aquilonia Yarrow
• Formica cunicularia Latreille
• Formica exsecta Nylander
• Formica exsectoides
• Formica fusca Linnaeus (F. (Serviformica) fusca)
• Formica lemani Bondroit
• Formica lugubris Zetterstedt
• Formica obscuripes Forel, 1886
• Formica polyctena
• Formica pratensis Retzius
• Formica rufa Linnaeus
• Formica rufibarbis F.
• Formica sanguinea Latreille Fabricius - said to enslave other ants
• Formica transkaucasica Nasonov

External links

• Myrmecos.net: Formica ant image gallery

References

1. cf. P. Huber via Darwin's Origin of Species, in Chapter VIII. Instinct

Source: adapted by the editor from Wikipedia, the free encyclopedia; from the article "Formica". Image Credit.

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