Dragonflies: Ancient aerial predators

Dragonflies and their ancestors have survived on Earth for over 300 million years. Fossils show that ancient dragonflies had wing-spans of over 28 inches. Today there are more than 80 different species that occur throughout the West, including about a half a dozen kinds in Malibu.

The name dragonfly comes from the Greek word for tooth, likely because of their very impressive chewing mouthparts. However, dragonflies are harmless to humans.

There are about 5,500 different species of dragonflies worldwide. Some are as colorful as birds and butterflies, with iridescent, metallic green and crimsons.

They all possess a similar design of a head, a thorax (sturdy midsection) and a long abdomen. Their head contains two compound eyes with as many as 30,000 lenses in each eye. They also possess two inconspicuous antennae which scientists believe act as a speedometer. Dragonflies can reach a top end speed of 60 kilometers per hour. 

Two pairs of large-veined wings are attached to the thorax, which tapers to a long, narrow abdomen with 10 segments.

While they have six legs, they are not used for walking. Instead, the back four appendages are important tools for perching, scooping up and handling prey, while the front two legs are used for grooming the eyes and face.

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Similar to humans, dragonflies use their eyes as the primary means of assessing the environment.

To catch food, these high-level predators employ huge hinged labiums (lips) with the lower one armed by pincers that grasp prey.

This basic design has produced such a finely tuned aerial predator, with superb vision and unmatched in-flight agility, that it has undergone no significant evolutionary modifications for millions of years.

Where do they live? Most anywhere near the presence of water: lake shores, streams, springs or peatlands. They predominate near standing water, spending their entire youth as larvae in water. What do they catch? Small fish, aquatic insects, crustaceans and tad-poles are all preyed upon. The way they move in proximity to water is even more interesting; Much like a jetski, dragonflies zip through the water by blowing water out through their rear ends.

Adult dragonflies are voracious predators who are not just limited to the water, though, eating just about any animal they can catch, including other dragonflies.

There are two types of aerial feeding. Hawkers are in constant pursuit of flying insects. Salliers, on the other hand, dart from a perch, capture prey and return to their perch.

Dragonflies avoid predators like birds, bats, flies, wasps and even other dragonflies by agile maneuvering. Bright blue colors of some species, that could attract predators, fade to gray at cooler temperatures when mobility is reduced.

They must eat a lot, because they shed their skin about 13 times before reaching adulthood. Most species over-winter as larvae and emerge the following spring or summer, metamorphize, shedding their hard outer shell as it splits along the back. Within a half an hour they are able to perform aerial maneuvers, including flying upside down.

When mating dragonflies lock together in copulation and form a wheel, sometimes it resembles the shape of a heart. The process can last for a few moments or hours.

Dragonflies have stood the test of time. They are awesome critters who depend upon healthy aquatic habitats that grace Malibu and through the West.

Earth Dr. Reese Halter is a broadcaster, conservation biologist and author of “The Incomparable Honeybee.”

13StarsManager
https://malibutimes.com
The Malibu Times is the first newspaper in Malibu, serving the community since 1946.

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