SPEED OF FLIES

Wairarapa Times-Age, 30 May 1938, Page 9

SPEED OF FLIES

SOME AMAZING ESTIMATES. GREAT CONTROVERSY RAGING. Controversy has arisen about ’ how fast can a fly fly. There are, of course, flies and flies—something like 40,000 known species. The activity of the housefly, formally known as Musca domestica, is of common observation. The deer bot fly, a relative especially disliked by deer, is the champion. Its speed has been estimated by Dr Charles H. T. Townsend, a natural scientist who has given time and thought to flies, at 818 miles an hour, which is about 78 times faster than sound, this being determined by checking the flight of a fly with the shutter of a camera. Writing in the Journal of the New York Entomological Society, Dr Townsend has said: ‘Regarding the speeds of cephenomya (bot fly), the idea of a fly overtaking a bullet is a painful mental pill to swallow, yet these flies can probably do that to an old-fashioned musket ball.” The higher up the faster they fly. “On 12,000-foot summits in New Mexico,” wrote Dr Townsend. “I have seen pass at an incredible velocity what were quite certainly the males Of cephenomyia. ... As close as I can estimate, their speed must have approximated 400 yards a second.” But now comes Dr Irving Langmuir to dispute this conclusion. Dr Langmuir has been making experiments with an artificial bot fly in his laboratory, and writes about them in a recent issue of the magazine, “Science.” No fly, contends Dr Langmuir, could fly as fast as that. For one thing, the blunt head of the bot fly would encounter an air pressure of about eight pounds per square inch, which would be the end of that fly. Such flight, moreover, would demand a fly about half as strong as a horse, which seems too much to expect of a fly; and would also require a food consumption of something more than its own weight every second, which seems rather deterrent. More than that, if the flying fly flew accidentally into some innocent bystander it would penerate the innocent bystander like a bullet, and no such accident, which would certainly be “news,” has yet been reported. Observing his own home-made bot fly flything through laboratory space at the end of a silk thread, Dr Langmuir found that at 64 miles an hour he could not see it at all.

The controversy seems rather a case of eye-witness versus circumstantial evidence. Is a real bot fly flying outdoors more visible than an artificial bot fly in a laboratory? And, if so, how does the flight of a blunt-headed bot fly fit in with the prevailing notion that really to go fast anything must be streamlined?