Resource: Primitive Insects of the Congaree Swamp

According to the fossil record, insects were the first animals to fly. Insect wings are thought to have evolved from gills. Because dragonflies and mayflies begin their lives as aquatic insects, they are considered more primitive than insects that do not pass through an aquatic stage. Wings evolved about 320 million years ago as a locomotive and self-defense mechanism and are the most important factor in determining insect classifications.

Other traits that scientists use to classify insects and use as clues to fit them into the evolutionary record include wing structure, eye structure and behavior. While butterflies have more advanced folding wings with scales, the more vulnerable dragonfly wings lack scales and lay flat while at rest. Beetles have wings that act as protective sheaths, and wasp wings have a more membranous structure. Other indicators of evolutionary hierarchy are insect behavior and simple versus compound eyes. Insects such as ants or bees that exhibit social behavior and insects with compound eyes are also considered more advanced.

While dragonflies are carnivores, about 360,000 of the 750,000 known species of insects, primarily caterpillars and moths, eat plants. The plants and slow-moving water at Congaree Swamp provide insects with the habitats and resources they need to complete their life cycles. Insect species live for varying amounts of time but they all go through some kind of metamorphosis, entering into various stages through molting. The larval stages of dragonflies and mayflies both begin in water, and like many aquatic insects, both are equipped with tracheal gills. Although they differ in placement, structure, and function, all tracheal gills in aquatic insects serve to disseminate dissolved oxygen from the water throughout their bodies by way of networked tubes. Scientists believe that wings evolved from the gill-like structures of ancient crustaceans and aquatic insects.

The juvenile naiads or nymphs of dragonflies remain aquatic for about five years, whereas the juvenile nymphs of mayflies remain aquatic for about one year. In the adult stages, mayflies only live from a few hours to a few days for the sole purpose of reproduction, while adult dragonflies can live as long as four months. Adult dragonflies feed on juvenile dragonflies, as well as mayflies or any other winged insects in the swamp environment.

To learn more about the Congaree Swamp, check out Flood Plain and Higher Ground Habitats, Root Systems of Trees at the Congaree Swamp , Reptiles of the Congaree Swamp, and Diversity of Hardwoods at Congaree Swamp.

To learn more about life cycles, check out Ladybug Pajama Party, Metamorphosis: Change of Plans, and the Life Stages Cards.

To find out more about insect evolution, check out Fossils.

To learn more about insects that fly, watch Robofly.

To learn more about animal classification, check out Animal Classification Game.

• What do a glistening dragonfly's wings indicate?
• What does a dragonfly's diet consist of?
• Why are zebra swallowtail butterflies so prevalent in Congaree National Forest?
• What do you think would happen to the Zebra swallowtail butterfly if the paw paw tree population decreased? Are there zebra swallowtail butterflies where you live? If not, how might you explain their absence?
• Imagine taking someone on a similar walk through the area where you live. What animals do you think you might see and point out? What do you think are some particularly interesting insects, and what is it about them that makes them interesting to you?