Amazon ant
| Amazon ant | ||||||||||||
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Amazon ant ( Polyergus rufescens ) |
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| Polyergus rufescens | ||||||||||||
| ( Latreille , 1798) |
The Amazon ant ( Polyergus rufescens ) is a species of ant from the subfamily of the scale ants (Formicinae).
Polyergus rufescens is a highly specialized "obligatory slave hunter", that is, it can no longer survive without "slave ants". Amazon ants regularly raid the nests of certain species of the genus Formica , steal larvae and pupae there and transport them back to their own nest. There, the stolen larvae and pupae are reared by existing "slave ants" and take care of the Amazon ants.
features
The workers are red-brown and 5-7 mm long, the queens are dark brown and 8.0-9.5 mm long, and the males are black and 6.0-7.5 mm long. The mouthparts are highly specialized in adaptation to the slave hunter's way of life. The mandibles are transformed into effective killing tools. They are sickle-shaped and have a very sharp cutting edge that is also finely serrated. With these mandibles, Amazon ants can penetrate heavily armored body parts such as the head or chest of other ants very quickly. The maxilla and the labia , however, are greatly shortened and probably no longer functional. The antennas are 12 sections.
distribution and habitat
The species is very rare. It settles in Central and Southern Europe . In Germany , their occurrence is limited to the warm regions, the most common of which are Amazon ants in the shell limestone regions of Thuringia , Saxony , Hesse , Bavaria and Baden-Württemberg .
It loves warmth and inhabits dry and semi- arid grasslands on the plains and in the hill country. Dense populations of at least one suitable host ant from the genus of the forest ants ( Formica ), z. B. the red-backed slave ant ( Formica cunicularia ), the gray-black slave ant ( Formica fusca ) or Formica rufibarbis .
Way of life
Amazon ants have been described repeatedly since the 18th century for their highly efficient slave hunts. The host nests are localized by scouts. During their search, these create a scent trail made up of pheromones . Once a suitable nest has been found, the scout runs back to its home nest. There he immediately recruits all available workers; this can be a few hundred up to 1500 individuals. This recruitment is also very likely to take place via volatile pheromones. The raids can go up to 85 m even in difficult terrain.
Until the mid-1990s it was assumed that the recruited army would run to its destination on the scout's scent trail. Recent studies have shown, however, that this is only partially true, because the workers of P. rufescens can navigate to a certain extent . The scout and the amazon ants at the head of the army only use polarized UV light from the sky for orientation and do not follow the scout's scent trail. Ants in the middle also use UV light for their bearings, but also follow the scent trail of the leading ants. On the way back to their own nest, the ants follow the scent trail of the army, but use the sky light to correct the route towards the nest.
The looting takes place largely without a fight, as the residents of the host's nests attacked are prompted to flee the nest immediately by a so-called “propaganda apheromone”. They climb with parts of the brood on blades of grass or hide near the nest. P. rufescens does not weaken the attacked ant colony more than necessary, as it can then attack it repeatedly. Only ants that engage in a fight are killed by biting the head capsule or the body. The Amazon ants run back to their own nest with their prey. The larvae and pupae are brought into the nest or placed in front of the entrance and entered and cared for by the slave ants.
In medium-sized to large nests of P. rufescens , the proportion of slave ants is 80 to 90%. Since the slave ants cannot reproduce in the nest of P. rufescens , new slaves have to be brought in regularly. In one case, workers in a large Amazon ant nest carried out 41 raids over 33 summer days, and around 40,000 larvae and pupae were captured.
The host ants apparently hardly have any means of defense against the attacking army of P. rufescens . In a study in Bavaria , however, it was found that the aggressiveness of female workers of the host species F. rufibarbis against P. rufescens workers increased sharply during the raids of P. rufescens (late June to mid-September). It is very likely that this increase in aggressiveness is aimed at killing the individually operating scouts of P. rufescens and thus serves to avoid raids.
nutrition
P. rufescens is no longer able to take in food independently. The slave workers feed the workers with liquid secretions.
Reproduction
The sex animals swarm in Central Europe from mid-July to early September. The majority of the young queens fly out of the nest. However, some of the queens go along with raids, occasionally stop and release a sex pheromone from the mandible gland. After a few minutes, males fly up and mate with the queens. The queens then immediately throw off their wings and take part in the raid. You can invade the nest of a host species on your own and kill the host queen or settle in the nest of the attacked ants and thus establish a new colony.
Danger
According to the Red List of Germany, the Amazon ant is threatened with extinction (Category 1). As a heat-loving inhabitant of dry grasslands, the species is threatened on the one hand by abandonment of use and encroachment, and on the other hand by direct or indirect fertilization of its habitat.
Individual evidence
- ↑ a b Heiko Bellmann : bees, wasps, ants. Hymenoptera of Central Europe . Franckh-Kosmos, Stuttgart 1995, ISBN 3-440-09690-4 .
- ↑ Grasso, DA, A. Ugolini, R. Visicchio & F. Le Moli 1997: Orientation of Polyergus rufescens (Hymenoptera, Formicidae) during slave-making raids. Animal Behavior 54: pp. 1425-1438.
- ↑ D'Ettorre, P., E. Brunner, T. Wenseleers & J. Heinze 2004: Knowing your enemies: seasonal dynamics of host-social parasite recognition. Natural Sciences 91: pp. 594-597.
literature
- P. D'Ettorre, E. Brunner, T. Wenseleers & J. Heinze: Knowing your enemies: seasonal dynamics of host-social parasite recognition. In: Natural Sciences. 91, 2004, pp. 594-597.
- DA Grasso, A. Ugolini, R. Visicchio & F. Le Moli: Orientation of Polyergus rufescens (Hymenoptera, Formicidae) during slave-making raids. In: Animal Behavior. 54, 1997, pp. 1425-1438.
- Bernhard Seifert: Ants: observe, determine. Naturbuch Verlag, Augsburg 1996, ISBN 3-89440-170-2 .
