Flying things abound in our desert—insects, birds, and bats. Sometimes it seems as if every other animal can take wing. Looked at from a different perspective, however, flight is a rarity that—to the best of our knowledge—evolved only four times. The vertebrates, the back-boned group to which we belong, claims the most successes, with birds, bats, and the extinct, reptilian pterodactyls.
Perhaps more amazing, though, are those insects who evolved flight. The flying vertebrates all have modified forelimbs to form their wings, albeit in three distinctly different ways. The insects, though, preserve their primitive three sets of legs, the wings originating separately from the body wall. Typically, evolution works by modifying an already present structure for a new use—but what organ could have been the basis for insect wings?
With an inadequate fossil record of early insects, scientists can only
speculate. One scenario suggests evolution from projections originally evolved for
radiation and absorption of heat. Until we can come up with testable hypotheses,
though, speculation will remain just that—just-so stories rather than science.
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.