Certain living organisms conjure scenes of the past in my paleontologist’s brain. Seeing a pelican skimming the crests of waves over Galveston Bay spark thoughts of pterosaurs gliding above the Cretaceous Niobraran Sea of western Kansas. Dragonflies bring visions of sweltering Late Paleozoic coal swamps teeming with monstrous arthropods.
Despite knowing that some insects are endothermic (“warm-blooded”) and are active over a wide range of temperatures, I was surprised to see a variety of active dragonflies on a recent chilly mid-November day at Lafitte’s Cove, Galveston Island, Texas. Perhaps this surprise was because of my bias toward thinking of dragonflies as a hot weather phenomenon.
In general, dragonflies fall into two types: “flyers” and “perchers.” Flyers like Green Darners (Anax junius) are endotherms, their elevated body temperatures largely the result of physiological processes supporting their highly active lifestyles. Perchers like Blue Dashers typically are closer to what are commonly called ectotherms, or “cold-blooded” organisms. These creatures regulate their body temperatures primarily through behavioral mechanisms like basking in the sun to raise body temperature, or conversely, as in the case of Blue Dashers, adopting the “obelisk posture.” In the obelisk posture, the abdomen is pointed toward the sun, thus decreasing the profile illuminated by the sun.
In any case, a major source of avian nutrition has stretched much deeper into the cool weather than I expected—and with it my dragonfly photography!
“I tried to discover, in the rumor of forests and waves, words that other men could not hear, and I pricked up my ears to listen to the revelation of their harmony.”—Gustave Flaubert, November
©2013 Christopher R. Cunningham. All rights reserved. No text or images may be duplicated or distributed without permission.