Distribution

1. Africa, southern and southeast Asia
2. D.R. Congo, Zambia
3. Central America, northern South America
4. Worldwide
5. Southern Sri Lanka
6. Worldwide, from warmer to tropical climates
7. Worldwide
8. Africa and Southeast Asia
9. Southern USA, Central and South America
10. Americas, Southeast Asia and Western Pacific Islands
11. Pacific Islands, Alaska
12. Central and northern South America
13. Southern Europe, eastern and southern Africa, southern Asia
14. Central and South America
15. Northern Brazil
16. Australia
17. Worldwide
18. Southern Central America and northern South America
19. Worldwide
20. Worldwide, from warmer to tropical climates
21. Worldwide, from warmer to tropical climates

Biology

"At this moment, more than one thousand trillion ants are scurrying all over the Earth. If every human climbed aboard one side of a scale, and every ant crawled onto the other side, the scale would just about balance." (cited from AntWeb).

Ants are of great significance not only in terms of numbers, but also ecologically. As "mega-decomposers" they break down vast amounts of organic material. As diggers they play an important role in aerating the soil. They form the most varied symbiotic associations with all kinds of plants, arthropods and fungi and count among the most efficient predators in the world. At present (2010), there are 11,700 known species of ants, and experts presume that as many species again exist throughout the world. They are currently divided into 21 subfamilies and 283 genera. 

Most species form highly developed societies with usually a single queen, workers (females) and males. In addition, many species have workers of various morphological forms, which carry out different functions. Thus there are often soldiers, which are responsible for the defence of the colony. The males and often also young queens possess wings, while these are absent in workers and soldiers.    

Ant colonies are usually very numerous. Several species of Harvester ants form the largest colonies, with 1 million or more animals. Most ants build their nests underground, but some build them aboveground, for example in hollow tree trunks or in the form of papery nests that hang from the branches of trees. Army ants are nomadic and thus do not build nests, but rather form simple temporary "camps" in which the individuals huddle together in suitable places; the brood is always carried along by the colony.

As with bees and wasps, the majority of ant species possess a fully developed venom apparatus. In the Dolichoderinae and Formicinae and some Myrmicinae the venom glands are still present, while the sting has regressed in the course of development. Nonetheless they can defend themselves effectively by biting with their mandibles and smearing venomous secretions into the wound. Examples of this type of ant are the Southern wood ant (Formica rufa) and Carpenter ants (Camponotus sp.), both commonly found in Europe.

Fig. 4.48 Solenopsis sp.

Risk

Ant stings or bites are unpleasant, but are generally limited to local effects, even in the case of multiple stings. However, they can be dangerous if allergic reactions occur in pre-sensitised patients. In principle, this is possible with all ants, but evidently occurs only rarely.

Problematic species are known to exist in southeast USA. These are the introduced species Solenopsis invicta and S. richteri (Red and Black imported fire ants) from the subfamily Myrmicinae. Although other Solenopsis species are native to the USA, these are medically insignificant compared to the two introduced species. In the first half of the 19th century they came with cargo ships from South America to the port of Mobile, Alabama, and from there they colonised large areas, in particular S. invicta. The invasion is still underway and it is feared that they will also become established in southwest USA.

The imported fire ants are not only common in rural regions but also in urban areas. They generally do not enter houses. They are characterised by aggressive defensive behaviour, in that they sting fiercely several times in succession. In their areas of distribution in the USA they are the main cause of hymenoptera sting allergies, ahead of honey bees and wasps. Between 30 and 60% of the population in urban areas is stung every year. Stings are most common during the summer months, and those most affected are children. The incidence of anaphylactic reactions is estimated to be 0.6–1% (DeShazo et al. 1990). Nothing is known of the medical significance of S. invicta and S. richteri in their native South American habitats.

On the basis of a survey in Tasmania, Australia, it was found that so-called Jack jumper ants (Myrmecia pilosula, Myrmeciinae) represent a serious cause of hymenoptera sting allergies there. This species is also common in southern Australia. The workers grow to around 1 cm in length and have yellow or orange legs. They are considered highly aggressive, as they can jump at their victim from a distance of up to 10 cm in order to sting. 49 of 100 people surveyed who had been stung by these ants showed generalised allergic reactions without being able to remember prior stings (Clarke 1986).

Literature (biological)

Akre and Reed 1984, Blum 1984, Blum and Hermann 1978, Lofgren et al. 1975, Hölldobler and Wilson 1990, 2009, Bolton 2003

AntWeb

Tree of life web project