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Mims: Crane flies could signal end of drought
By Forrest Mims : March 23, 2012 : Updated: March 26, 2012 8:18am
Photo By Forrest M. Mims III/for the Express-News
This large crane fly is among many that are visiting the Mims place. The arrow points to a haltere, an organ that assures stable flight.
Have you recently noticed flying insects that resemble giant mosquitoes? These are crane flies, and their presence is a good indicator that drought conditions have ended, at least for now.
The photograph at right shows a crane fly perched on our garage door. The ends of the two most outstretched legs are 3.7 inches apart, which makes this a very large crane fly.
Texas hosts several species of crane flies, which generally emerge in February and March after spending months as larvae eating moist, decayed plant matter.
An imported European species eats roots of grass.
The life of an adult crane fly is much briefer than that of the larva. The male fly's sole objective is to find a mate, and the female's is to lay her eggs in moist soil. They do this while avoiding hungry birds and swats from people who think they are giant mosquitoes.
Crane flies do not bite or sting. Instead of killing those that enter your house, why not invest a few minutes watching their antics?
Of special interest are the pair of thin rods that end with a bulb-like object behind each of the crane fly's wings. These are called halteres, and they provide stability during flight. All flies have halteres, and the crane fly's large size makes its especially obvious. The arrow in the photo points to a haltere. When the wings of a crane fly are flapping, the halteres vibrate in step with them. When the fly turns in flight, the inertia of the vibrating halteres tends to keep them in the same position as they were before the turn began. This causes the shaft of the halteres to press against sensors behind the wing that tell the fly the angle and direction of the turn.
Like most insects, fossilized crane flies look much like their modern descendants. Two crane flies are in my little fossil collection. One is impressed in gray shale, and the other is encapsulated in a transparent blob of Dominican Republic amber. The crane fly in amber looks like it was trapped only hours ago in the tree sap, which hardened into amber over eons of time. It even has halteres much like the living fly in the photo. These fossils show that the earliest known crane flies came equipped with a state-of-the-art navigation system, a guidance and control analog computer, a pair of video cameras and the genetic code to pass along precise details for replicating all this and much more in their tiny eggs. I've enjoyed reminding biologist friends about these facts during friendly discussions about the debate over creation and evolution.
Forrest Mims III, an amateur scientist whose research has appeared in leading scientific journals, was named one of the 50 Best Brains in Science by Discover Magazine. His science is featured at www.forrestmims.org. Email him at email@example.com.