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No. 33: May-Jun 1984

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Prisoners Of The Boundary Layer

Wings were an inspired evolutionary development. They permit the geographical dispersal of many species, especially insects. But nature, ever-innovative, has other aeronautical techniques up her sleeve. Consider the tiniest insects that do not possess wings. It is difficult for large animals like ourselves to realize that these tiny creatures are actually prisoners of the so-called "boundary layer" of air hugging all surfaces. The thin boundary layer is stagnant very close to the surface. Any tiny in-sect wishing to take advantage of wind-dispersal to propagate the species farther afield must somehow breach this layer. Some of the scale insects have in their instar phases developed the trick of rearing up on their hind legs, penetrating the boundary layer, and presenting a high-drag surface to the wind. (Many climb along plant surfaces inside the boundary layer to exposed areas before exhibiting this behavior.) The wind plucks them off the plant and carries them off to new territories. The authors think this may be convergent evolutionary strategy for many minute insects.

(Washburn, Jan O., and Washburn, Libe; "Active Aerial Dispersal of Minute Wingless Arthropods.....," Science, 223:1088, 1984.)

Comment. The fact that these insects are shaped like airfoils (i.e., aircraft wings) is also interesting.

Scale insects Scale insects (first instar phase).
A. In the slow-moving boundary layer.
B. Rearing through the boundary layer to present a high-drag cross section to the wind.

From Science Frontiers #33, MAY-JUN 1984. 1984-2000 William R. Corliss

Science Frontiers Sourcebook Project Reviewed in:

Quotes

  • "A sourcebook of unexplained phenomena is therefore a valuable addition to a collection of scientific literature. William R. Corliss has provided this in the past with his source books of scientific anomalies in several subjects, and now he has provided it for astronomy. He has done an excellent job of collecting and editing a large amount of material, taken in part from scientific journals and in part from scientific reporting in the popular or semi-scientific press." -- "The Mysterious Universe: A Handbook of Astronomical Anomalies", reviwed by Thomas Gold, Cornell University, in Icarus, vol.41, 1980

  • "An interesting, systematic presentation of unusual weather [..] This book is recommended for a general audience" --"Corliss, William R., Tornados, Dark Days, Anomalous Precipitation, and Related Weather Phenomena, Sourcebook Project, 1983.", revieweed in Choice, September 1983
  • "..the science is necessarily somewhat speculative, but Corliss's symthesis is based on reputable sources." -- "Corliss, William R. (Compiler). Lightning, Auroras, Nocturnal Lights, and Related Luminous Phenomena" reviwed by Joseph M. Moran, Univ. of Wisconsin in Science Books and Films, Sep/Oct 1983

  • "Before opening the book, I set certain standards that a volume which treads into dangerous grounds grounds like this must meet. The author scrupulously met, or even exceeded those standards. Each phenomenon is exhaustively documented, with references to scientific journals [..] and extensive quotations" -- "Book Review: The moon and planets: a catalog of astronomical anomalies", The Sourcebook Project, 1985., Corliss, W. R., Journal of the Royal Astronomical Society of Canada, Vol. 81, no. 1 (1987), p. 24., 02/1987