Bill Dunson, born in rural Georgia, skipped 12th grade and went directly to Yale. Bill subsequent-ly received a PhD in Zoology from the University of Michigan, studying softshell turtles. Bill is Professor Emeritus of Pennsylvania State University thanks to a career spent entirely at that institution, teaching and doing research on the physio-logical ecology and ecotoxiciology of reptiles, amphibians and fish. Always curious about nature, Bill has dedicated his life to learning and sharing his knowledge with others. He has served on many advisory boards here in Southwest Florida to preserve the water that gives life to our region.

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What the Heck is That?

This might be your response when seeing this shed exoskeleton of a larval dragonfly, in this case a green darner, on the stem of a plant growing in a pond. We have a lot of these around our pond on cattails, reflecting the many nymphs of green darners that have emerged this Summer.

Green darners mate and lay their tiny eggs in ponds, which hatch and become ferocious aquatic predators. They grow into a large nymph (several inches long) that catch and eat other invertebrates and small vertebrates. When mature as a larva, they crawl from the water and attach themselves to a stick or leaf and undergo a complete metamorphic transformation from a crawling insect in water to a marvelous flying machine, the dragonfly. The larval skin splits along the back and the adult dragonfly emerges. This complete metamorphosis is quite different from the gradual increase in size, without any significant change in structure, undergone by insects such as the grasshopper.

One likely explanation for the success of such a complete metamorphosis (also used by butterflies and moths) is that the feeding of the young does not compete with the completely different feeding habits of the adults. This may then allow for a higher density of predatory dragonflies than might be possible if both young and adults ate similar foods. Remember that predators cannot achieve the population numbers of the herbivores and predators that they feed upon.

In any case the transition from a lowly crawling bug into the remarkable flying creature that is the dragonfly is just amazing!

Bill Dunson
Galax, VA & Englewood, FL