Bivouac nest

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Bivouac of the driver ants

The bivouac nest or bivouac is a mobile free nest or earth nest of ant species without a permanent nest location. Freinisters are driver ants (of the subfamily Ecitoninae ) as well as from the ponerine genus Leptogenys . Dorylinae and Aenictinae are earth-nesting, but form bivouac-like aggregations within the earth nests. Bivouac nests are clusters of female workers who cling to one another. Apart from the animal carcasses, no building material is used.

Driver ants bridge

The nest is close to the ground between leaves or in ground or wooden hollows, but there are also nests hanging freely between branches. Bivouac nest breeding and possibly present are Trophobionten (z. B. mealybugs ) of the bodies of the workers who are mutually the Tarsalklauen (pretarsus) cling, protectively coated. Since the construction of the nest does not require any material, it can be set up and dismantled very quickly, which makes the mobility of driver and wandering ants possible in the first place. But not only on the occasion of hikes, also at the turn of the day, when the workers swarm out, the nest seems to dissolve in order to gain volume again in the evening.

State size

Up to 700,000 workers can populate a bivouac about 1 m in diameter.

Counts of several bivouacs of Dolichoderus cuspidatus the size of a fist or child's head revealed a population of at least 10,000 migrant shepherd ants workers, around 4,000 larvae and pupated ants, over 5,000 mealybugs and one (i.e. monogyner) ergatogyne (i.e. worker-like queen). Male winged ants were seen in large numbers during the dry season (January – February) and during the monsoon season (September – October). The colonies multiply by division.

Bivouac as a raft

Bivouac raft of the red fire ants
Fire ants bivouac raft

Red fire ants ( Solenopsis invicta ) survive floods by chaining the individual female animals and larvae with their bodies to form a raft. This raft is a construction that is stable and strong enough to transport an entire state on a river like the Amazon . It should be noted that overcoming water surfaces is generally a major challenge for insects living on land. The raft, which is also called a bivouac (also: “ant grapes”) appears chaotic to the human observer and consists of a “mat” of living bodies from older workers. It is formed when the animals firmly connect to their neighbors - on average 4.8 neighboring animals - via feet and mouthparts , which results in an average of 14 connection points per animal, large individuals have up to 21. Small and large animals prefer to take alternating positions the network. The ability to swim results on the one hand from the fact that the body surface of the animals consists of a water-repellent cuticle , which contains a lot of hydrophobic chitin as a surface component, on the other hand, the animal bodies keep air bubbles under water with the help of their cuticle bristles. From time to time, animals submerged must replenish their external air supplies. To do this, they detach themselves from the bandage, are replaced by moving ones and crawl through channels between the other animals to the surface of the air. Larvae can bind more air bubbles, which is why rafts with higher larvae numbers swim more stably.

The rafts can have a diameter of up to 45 cm. The raft is insensitive to large waves .

The rest of the animals are freely movable on the mat, but in a confined space with free passageways. The rafts can consist entirely of female workers, which is a questionable survival strategy. Usually they also harbor brood and queens, often symbionts and male ants as well. However, it has also been observed that male ants were prevented from taking up space on the raft. Lone ants drown.

Several species of ants from different continents have the ability to form bivouac rafts: Solenopsis geminata (Brazil - Pantanal, Colombia, Venezuela - Llanos), red fire ant ( Solenopsis invicta in southern USA and South America), Camponotus compressus (India), yellow shadow ant ( Lasius umbratus in Europe, Asia, North America), Myrmica gallienii (Germany), red garden ant ( Myrmica rubra , first observed in 1997 in Eastern Austria), Dorylus arcens (West Africa) and possibly others.

In fire ants, the formation of the bivouac raft is triggered by permanent light drumming, as if by incessant rain. In other ants, too, such as Lasius or Campnotus , vibrations trigger activities like rain.

Web links

Single receipts

  1. ^ Andreas Weißflog: Free nesting of ants (Hymenoptera: Formicidae) in the crown region of humid tropical forests of Southeast Asia . Dissertation at the Department of Biology and Computer Science, JW Goethe University in Frankfurt am Main. 2001, urn : nbn: de: hebis: 30-32871 ( Online [PDF; 3,9 MB ]).
  2. ↑ WH Gotwald, Jr .: Army ants: the biology of social predation. In: Cornell University Press. Ithaca, 1995.
  3. ↑ U. Maschwitz , S. Steghaus-Kovac, R. Gaube, H. Hänel: A South East Asian ponerine ant of the genus Leptogenys (Hym., Form.) With army ant life habits. In: Behav. Ecol. Sociobiol. Volume 24, 1989, pp. 305-316.
  4. ↑ a b c d Ulrich Maschwitz, Heinz Hänel: The migrating herdsman Dolichoderus (Diabolus) cuspidatus: an ant with a novel mode of life . In: Behavioral Ecology Sociobiology. Volume 17, No. 2, 1985, pp. 171-184.
  5. ↑ Jacques HC Delabie: Trophobiosis between Formicidae and Hemiptera (Sternorrhyncha and Auchenorrhyncha) to overview. In: Neotropical Entomology. Volume 30, No. 4, 2001, doi: 10.1590 / S1519-566X2001000400001 .
  6. ^ The praetarsus of insects ( Memento from August 29, 2008 in the Internet Archive )
  7. ↑ U. Maschwitz, H. Hänel: Dolichoderus cuspidatus: the first nomadic ant. In: Nature Malaysiana. Volume 11, No. 1, 1986, 18-23
  8. ↑ William B. Jackson: Microclimatic Patterns in the army ant bivouac. In: Ecology. Volume 38, No. 2, 1957, pp. 276-285.
  9. ^ TC Schneirla, Robert Z. Brown, Frances C. Brown: The bivouac or temporary nest as an adaptive factor in certain terrestrial species of army ants. In: Ecological Monographs. Volume 24, No. 3, 1954, pp. 269-296.
  10. ↑ a b c d e BJ Adams, LM Hooper-Bùi, RM Strecker, DM O'Brien: Raft formation by the red imported fire ant, Solenopsis invicta. In: Journal of insect science (online). Volume 11, 2011, p. 171, doi: 10.1673 / 031.011.17101 , PMID 22950473 , PMC 3462402 (free full text).
  11. ^ A b Ernesto I. Badano: Species richness and structure of ant communities in a dynamic archipelago: effects of island area and age. In: J. of Biogeography. Volume 32, No. 2, 2005, pp. 221-227, doi: 10.1111 / j.1365-2699.2004.01174.x .
  12. ↑ a b c Christian O. Dietrich, Birgit Schlick, Florian Steiner: Ameisen bei Hochwasser (Hymenoptera: Formicidae) - observations in Eastern Austria in July 1997. In: Myrmecologische Nachrichten 2, 1998, pp. 35-41.
  13. ↑ a b c Kathryn Knight: How fire ant architects connect to build balls. In The Journal of Experimental Biology 217, No. 12, 2014, pp. 2029-2029, doi: 10.1242 / jeb.108787 .
  14. ↑ Rolf Froböse: When frogs fall from the sky. The craziest natural phenomena . Wiley-VCH, Weinheim 2007, ISBN 3-527-31659-0 , pp. 170 (Explanation of the lotus effect of the insect wings).
  15. ^ Walter R. Tschinkel: The fire ant (Solenopsis invicta): still unvanquished. (PDF; 1.1 MB; pp. 126–128) In: BN McKnight: Biological Pollution: the control and impact of invasive exotic species. Issued by: Indiana Acad. Sci. Indianapolis 1993, pp. 121-136.
  16. ↑ Nathan J. Mlot, Craig A. Tovery, David L. Hu: Fire ants self-assembly into waterproof rafts to survive floods. In: PNAS . Volume 108, No. 19, 2011, pp. 7669–7673, doi: 10.1073 / pnas.1016658108 quoted in: Fire ants cuddle up to a lifeboat. In: Spiegel Online . April 26, 2011.
  17. ↑ a b c d e f g h C. Anderson, G. Theraulaz, J.-L. Deneubourg: Self-assemblages in insect societies. In: Insectes Sociaux. Volume 49, No. 2, May 2002, pp. 99-110.
  18. ↑ Adele M. Fielde, George H. Parker: The reactions of ants to material vibrations. In: Proceedings of the Academy of Natural Sciences of Philadelphia. 1904, pp. 642-650.