'Deer Fly' flight speed, and scaling
fnkwp at AURORA.ALASKA.EDU
Fri Jan 23 13:34:26 CST 1998
Robin Panza brought up the case of the '914 mph deerfly', and Thomas Lammers
brought up the issue of scaling as relevant.
Both of these isues were discussed in some detail on Entomo-L a couple of
years ago--here is some information:
The high-speed fly (not a deer fly, but a bot fly) claim was made
in the following paper:
Townsend, C. 1927. On the Cephenemyia flight mechanism and the
daylight-day circuit of the Earth by flight. J. N. Y. Entomol. Soc. 35:
and also in an earlier paper:
Townsend, C. 1926 Around the world in a Daylight Day: a Problem in Flight.
The Scientific Monthly. 309-311
I have copies of both papers on hand.
Townsend claimed to have observed an Oestrid fly (bot fly) flying at over
400 yards per second. Note that his 'measurement' had only one significant
figure, so this means he was claiming 800 mph, or 1300 km/hr. His measuring
apparatus was his unaided eye, his measuring technique was: The insects are
blurred in flight, therefore they _must_ be flying at over 400 yards per
second. This is, of course, arrant nonsense. (Townsend was a Tachinid
taxonomist, and according to D.M. Wood in Ottawa, his taxonomy wasn't much
better than his physics.) Townsend's 'measurement' had nothing to do with
scaling, but purported to be an absolute speed determination.
I have never heard the figure of 914 mph for Townsend's claim,
and have no idea where it came from. It does not match Townsend's own
numbers. All the references in the popular literature that I have seen
use the figure of 800 mph.
It was Irving Langmuir who published the paper showing that the
fly's head would be crushed by air pressure at such a speed.
I discussed the issue of insect strength on Entomo-L. It turns out
that the actual _strengths_ of most insect muscles are somewhat inferior to
human muscles. If human beings could be reduced to the size of an insect
and still function, they could perform even more remarkable feats. The
ability of small organisms to lift many times their own weight, jump many
times their length, etc. is purely an artifact of scaling and has nothing
to do with the superior strength of their muscles. There is one exception
ti all this--insect flight muscle is unique in its total power output,
although not in the forces exerted.
fnkwp at aurora.alaska.edu
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