Dragonflies and damselflies

I thought I might write about one of my favorite insects. I mean, I think just about all insects are pretty awesome, but we all have favorites…right? Anyhow, I have been fascinated by dragonflies for as long as I can remember. I grew up on a farm, surrounded by fields, and so I spent much of my childhood playing outside. One of my favorite places to explore was the creek (that is the polite name for a drainage ditch between fields), where dragonflies could be seen zipping about while damselflies hovered delicately along the bank or in a shady stand of trees.

So to begin, what is a dragonfly, and how is it different from a damselfly? Both are predatory insects that belong to the order Odonata. Morphologically, they possess very large eyes, two pairs of wings that can be operated independently of one another, and a narrow, elongated abdomen. Dragonflies, belonging to the suborder Anisoptera, tend to be larger than damselflies, with much larger eyes that actually meet on the top of their head. Damselflies, belonging to the suborder Zygoptera, have smaller eyes that sit on either side of the head, and a narrow, stalk-like abdomen. Another important distinction between the two is wing structure. The wings of a dragonfly extend out to its side when at rest, while the wings of damselflies are brought together at rest, extending either above or along the abdomen. Furthermore, the shape of the hind pair of wings is different from the forewings in dragonflies, whereas the wings of a damselfly are all similar in size and shape. Dragonflies and damselflies can be found in a stunning array of colors. While we often tend to associate the colorful and ostentatious colors with insects and other animals that dwell in rain forests or tropical locations, vividly colorful dragonflies and damselflies can be found just about anywhere.

As adults, dragonflies are among the swiftest and most agile of the flying insects. The majority of flying insects use what are known as indirect flight muscles to control the movement of their wings. An insect’s shape is maintained by a rigid exterior shell called an exoskeleton, rather than the rigid interior framework (skeleton) possessed by vertebrates. Though the exoskeleton of an insect is relatively tough and rigid, it is not inflexible. Indirect flight muscles, as the name implies, do not attach directly to the wings, but instead attach to the exoskeleton of the thorax, the portion of the body to which the wings are attached. When the muscles contract, it deforms the thorax, in turn causing the wings to move.

The aerial prowess of dragonflies is largely due to the evolution of direct flight muscles that are unlike those of most other insects. The flight muscles of a dragonfly attach directly to each wing, allowing the dragonfly to move each wing independently of one another.

Check out this brief video showing slow-motion take-offs and landings:

http://www.youtube.com/watch?v=HdKxmvcRxls

The result is that dragonflies can perform some rather amazing maneuvers, making them not only fascinating to watch, but also fierce predators. The adults feed on all manner of insects, and are especially useful for preying on mosquitoes. You will normally find them somewhere close to water because that is where they reproduce. Dragonflies and damselflies undergo hemimetabolism, or incomplete metamorphosis, which differs from the holometabolism (complete metamorphism) exhibited by insects such as flies, beetles, butterflies, moths,  etc. Think about a moth, which begins life as an egg, hatches to become a caterpillar during the larval stage, forms a cocoon to protect itself during the pupal stage, then finally hatches as an adult. This is complete metamorphism. Incomplete metamorphism skips a bit. The egg hatches to become an immature version of the adult, known as a nymph or a naiad, which grows progressively larger until it becomes an adult. The term naiad is used to refer to insects like dragonflies whose larvae are aquatic.

Dragonflies actually spend much of their life underwater, sometimes for years, before crawling out of the water to molt and emerge as adults.

Obviously the naiads appear to differ quite greatly from the adult stage, but they are every bit the vicious predators. In fact, dragonfly and damselfly naiads have this amazing mouthpart, which is essentially the lower “lip”, that they can rapidly extend to grab their prey. Immature dragonflies hunt other aquatic insects, larvae, and even fish or amphibians. Check out the video below.

http://www.youtube.com/watch?v=W557aSVdW_g

Imagine if those things were huge…and trying to catch you…and you were on a spaceship. Oh wait. Somebody already did. Definite nightmare fuel.

So in conclusion, dragonflies (and damselflies) are pretty bad-ass insects, both as the immature aquatic alien horror, and as the adult aerial daredevil. Be glad that they are tiny and we are not, or we would be called lunch.

Thanks for reading!

Category(s): Entomology

2 Responses to Dragonflies and damselflies

    Dana Czapanskiy says:

    Thoroughly enjoyable read, interesting, fun facts, great links. Write more. Loved it.