True flight is shared only by insects, bats, and birds. Examples of other animals that are capable of soaring are flying fish, flying squirrels, flying frogs, and flying snakes. The capacity for flight in insects is believed to have developed some 300 million years ago, and initially consisted of simple extensions of the cuticle from the thorax. The success of insects during development of flight was due to their small size. Of course, not all insects have developed wings, these including such groups as spring-tails and silverfish. Some parasitic groups are believed to have lost their wings through evolution. When wings are present in insects, they commonly consist of two pairs. These include grasshoppers, bees, wasps, dragonflies, true bugs, butterflies, moths and others. The outer pair of wings of beetles commonly are quite hard and not functional in flight. The ability to fly is not determined by the number or size of wings. Some insects with large wings, such as Dobsonflies and Antlions, are relatively poor fliers, while bees and wasps with smaller wings are good fliers. True flies are a large group of insects with only one pair of wings, although they have small balancing organs known as halteres where a second pair of wings might develop. The halteres vibrate with the wings and sense changes of direction.

Flight is one of the primary reasons that insects have been successful in nature. Flight assists insects in the following ways:

Escaping from danger

Finding food

Locating mates

Exploring for new places to live

Flight in insects varies dramatically, from the clumsy patterns of some beetles and true bugs to the acrobatic maneuvers of dragonflies and many true flies. Flies in the Family Syrphidae (flower flies and hover flies) are capable of astounding feats, including moving forward, backward, sideways, and up and down. They can truly hover also, which is an uncommon ability in insects. Flight in insects is gained by muscles, not attached directly to the wings, that move the wings indirectly by changing the shape of the thorax.

The following records relate to the flight of insects:

Migration distance — Painted Lady Butterfly, from North Africa to Iceland, a distance of 4,000 miles. Fastest flight in insects — Sphinx Moths, speed of 33 mph. Fastest wingbeat — Midge, at 62,760 beats per minute. Slowest wingbeat — Swallowtail butterfly -- 300 beats/minute. Highest altitude — Some butterflies have been observed flying at altitudes up to 20,000 feet. Largest wings, modern — Wingspans of some butterflies and moths are the largest of all modern insects. Largest wings, extinct — The wingspans of fossil dragonflies, existing millions of years ago, were more than two feet.

A fascinating account of the speed of a Deer Bot fly, Cephanomvia pratti, was made by entomologist C. H. T. Townsend in 1926 by estimating the speed of the fly as it flew between mountaintops. Townsend published his findings, stating that the fly was able to accomplish a speed of 818 miles an hour. This figure has been repeated for decades, but is now believed to be quite impossible. Another common story involves the flight of bumblebees, which were studied by Antoine Magnan, a French zoologist, in 1934. His conclusions indicated that these insects could not fly at all.

Flights for food sometimes encompass distances of hundreds of miles, an example being African grasshoppers. These insects fly together in large groups, sometimes as many as 100 million individuals.

Monarch Butterflies are the best known example of flight for the purpose of migration. In the fall, Monarchs gather in great numbers and migrate across the United States to overwintering localities in Mexico. Anyone who has seen such accumulations of Monarchs will never forget the experience.

Selected References:

Armstrong, R. H. 1990. "Photographing insects in flight." American Entomologist, Volume 36, number 3.

Pringle, J. W. S. 1957. Insect Flight. Cambridge University Press, Cambridge, Massachusetts.

Snodgrass, R. E. 1930. How insects fly. Annual Reports of the Smithsonian Institution, 1929.

Prepared by the Department of Systematic Biology, Entomology Section,

National Museum of Natural History, in cooperation with Public Inquiry Services,

Smithsonian Institution

Information Sheet Number 96

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