Ballooning (spider)
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Ballooning is a term used for the mechanical kiting [1] [2] [3] that many spiders, as well as certain mites and some caterpillars use to disperse through the air; never is an actual lighter-than-air balloon formed; the silk has form enough to react with the wind to give lift and drag enough to mechanically kite the spider; researchers prominently applied the term ballooning for such dynamic kiting where the animal's body is the dragging anchor to the silken kite. Biologists also applied the term "balloon silk" to the threads that mechanically form the lifting and dragging system. Distinguish the mechanics from the biological literature term.
Many small spiders use silk threads for ballooning. They extrude several threads into the air and let themselves become carried away with winds--both updrafts and windward. Tiptoeing behavior occurs as a prelude to ballooning: The spider stands on raised legs with the abdomen pointed upwards. Although most rides will end a few meters later, it seems to be a common way for spiders to invade islands. Many sailors have reported that spiders have been caught in their ship's sails, even when far from land. (Heimer 1988)
It is generally thought that most spiders heavier than 1 mg are not likely to use ballooning (Suter 1999). Also, because many individuals die during ballooning, it is more unlikely that adults will do it than spiderlings. However, adult females of several social Stegodyphus species (S. dumicola and S. mimosarum), weighing more than 100 mg and with a body size of up to 14 mm, have been observed ballooning using rising thermals on hot days without wind. These spiders used tens to hundreds of silk strands, which formed a triangular sheet with a length and width of about one meter. (Schneider 2001)
[edit] References
- ^ Spiders By Ann R. Heinrichs. Google Books. She observes that the so called ballooning is like a kite or balloon; she is mechanically correct about the kite part, as no true balloon is ever formed by the spider as told in the other references.
- ^ Flying Spiders over Texas! Coast to Coast. Chad B., Texas State University Undergrad: He correctly describes the mechanical kiting of spider "ballooning".
- ^ Artificial and Natural Flight By Hiram Stevens Maxim. Chapter on "Flying Kites", the "Balloon Spider" is correctly seen as mechanical kiting.
- Heimer, S. (1988): Wunderbare Welt der Spinnen. Urania-Verlag Leipzig. ISBN 3-332-00210-4
- Suter, R.B. (1999): An aerial lottery: The physics of ballooning in a chaotic atmosphere. Journal of Arachnology 27: 281-293. PDF
- Schneider, J.M., Roos, J., Lubin, Y. & Henschel, J.R. (2001): Dispersal of Stegodyphus dumicola (Araneae, Eresidae): They do balloon after all! The Journal of Arachnology 29: 114-116. PDF
[edit] Further reading
- Dean, D.A. & Sterling, W.L. (1985): Size of ballooning spiders at two locations in eastern Texas. J. Arachnol. 13: 111-120. PDF
[edit] See also
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