Damsels and Dragons - the Insect Order Odonata

The Odonata (from the Greek odon-o meaning tooth), commonly known as dragonflies and damselflies, is a fascinating insect order. (In some areas, the term dragonfly is used for both groups.) Since this article is for the Internet Pond Society, I have emphasized pond species and activities that the reader, as a pond owner, might observe or perform.

Some of the images used here are linked from other web pages where the reader will find additional information, pictures or links. All sites were active when the article was submitted (Jan 31, 1997). Unless otherwise indicated all photographs are by the author ( details on the reproduction techniques and use restrictions)

Introduction

Dragonflies and damselflies are insects. As such, they have 3 prominent body parts - a head, a thorax to which the wings, in this case 4, and 6 legs are attached, and an abdomen. Their front and rear wings are not linked together, but can be operated independently. The dragonfly is an impressive insect, a master of the air, daring enough, in some cases, to hover almost within arm's reach in front of human invaders in its territory. At rest, its wings lie flat, at right angles to the body. The damselfly is generally much less impressive or conspicuous. It tends to be smaller and less robust, a much weaker flyer still capable of aerial acrobatics, but less active. At rest, damselflies hold their wings over their backs, either together or spread out in a v-shape. Damselflies usually stay close to a surface, while dragonflies can zoom up into the air and out of sight. Dragonflies and damselflies are predators throughout their lives.

Dragonflies and damselflies have been around for a long time. Impressive fossils of dragonflies with 27" wingspans have been found dating back over 200 million years. Today, the largest ones have wingspans about 5 to 6 inches.

As with many insects, dragonflies have played a significant role in some cultures. An article by Montgomery in 1972 lists 95 English terms used for dragonflies. With the current interest in topical postage stamps, there are now over 100 stamps from around the world that feature dragonflies either as the main design or a decorative addition.

Among the Odonata there is an amazing amount of variation, both in their life histories and their activities. These fascinating insects which fly around your pond for a short period are much older than you might think. Most of them have spent a much longer period of time as important aquatic predators.

Mating

Appendages that can be seen at the end of abdomen of the male are designed to lock into species-specific grooves and notches on the female in order to secure the two together for mating. The features on female dragonflies may be on the head alone or on the head and the front segment of the thorax. Female damselflies have features on the front segment of the thorax. Male and female dragonflies tend to wed in the air, sometimes with an audible impact. Damselflies become hitched together more quietly, often coming together on vegetation. Hitched pairs, particularly damselflies (just because they are generally more numerous), can often be seen flying about "in tandem" looking for mating sites.

tandem pair

tandem pair flying over open water (you can see the reflection)


The mating formation is called a wheel. Attached to the male by her head and/or the front segment of her thorax, the female curls her abdomen under her, reaching forward with the tip of her abdomen in order to pick up the sperm from the male's second abdominal segment. From the side, damselfly pairs appear sort of heart-shaped. Some dragonflies mate in the air, while others alight to mate (this may be the only time you get a good view of some species). Damselflies usually land to mate. In species that land, you can often see the legs of the female wrapped around the abdomen of the male for strain relief and support during mating. The male may assist the female by moving or curling his abdomen. Previously mated males can be distinguished if their abdomens have become damaged (dented) from the downward pressure of the females' legs. For some species, the mating time is very short, only a few seconds. For others, especially some of the damselflies, it can be up to several hours. (Perhaps this is why, Martin Peterson found that they were once regarded as a symbol of the love goddess, Freya.) Males and females of some dragonflies can be seen flying "in tandem" after mating, but this activity is more common among the damselflies.

Inter-specific sexual activity is normally discouraged by the lock-and-key aspect of the attachment process (it has been reported). Damage incurred from prior mating activity can allow some inter-specific activity.

Egg Laying

Depending on the species and/or the circumstances, the male may or may not be around while the female lays her eggs. Males can often be found guarding the female, chasing off other potential mates so that she can finish laying the eggs fertilized with his sperm. Some species go to extremes in mate guarding - the male doesn't release the female, but remains attached until she has laid at least some eggs. Tandem pairs can often be seen flying slowly among the vegetation, looking for oviposition sites.

For many species often seen in tandem, the female inserts each egg individually into some suitable vegetation, from dead wood to reeds, sometimes above the waterline, sometimes below, sometimes so far below that the males and females descend into the water breathing via a protective coating of air that gets trapped in the many fine hairs on their bodies. In cases where the eggs are laid above the waterline, several situations may occur. Sometimes the eggs are laid over water, and the newly emerged larva drops in. Sometimes, the vegetation dies and falls into the water, or becomes submerged after the rains.

egg laying

Archilestes californica (damselfly) tandem pair laying eggs


In D. Paulson's copyrighted image available through the University of Michigan, 6 pairs of the damselfly, Argia moesta, are ovipositing. In this case, the females generally have their abdomens seeking sites in or near the water while the males are approximately vertical.

In many cases where the female lays her eggs with the male nearby or absent, the female hovers over a suitable location, descending periodically to dip the tip of her abdomen into the water and wash the eggs off. The females of some species scatter their eggs from the air. Females have been known to become confused and attempt to lay eggs on unsuitable substrates such as oil and windshields.

If you are interested in allowing these creatures some space in your pond, observe where egg laying is occuring and make some allowance for this when you perform any maintenance. There may be preferred sites, some of which might include the more tropical plants in your pond (i.e. the ones you might take inside to overwinter).

Larvae

After the egg has hatched, the larva (also called a nymph or naiad) is a crytically colored, free living, aquatic predator. Larvae prey mainly on other aquatic insects, such as mosquito larvae or even other odonate larvae. Larger larvae may prey on fish fry. In turn, dragonflies are preyed on by a number of species, including fish and frogs. They may serve as hosts for certain aquatic mites and avian parasites. Many species live among the aquatic vegetation.

A damselfly larva is characterized by 3 fin-like appendages, called lamellae, at the end of its abdomen, The lamellae are important for respiration.

damselfly larva

damselfly larvae in water (Ohio Dept. of Natural Resources photo.)
(from the Rivers Online - Darby Creek Site)


Compared to damselfly larvae, dragonfly larvae are broader and less delicate looking. Dragonfly larvae lack the lamellae of the damselflies, relying on foliations in the rectal area for respiration.

dragonfly (Green Darner) larva

larva for a dragonfly known as the Green Darner
(from a Texas A & M study by Dr. Ann Kenimer on the Texas Water Resources Institute web site)

dragonfly larva

dragonfly larvae similar in appearance to those of many pond species
(from Texas A & M study by Dr. Ann Kenimer indicated above)


As with all insects, the larvae undergo a series of molts as they grow and develop. While some species have relatively short larval development times (1-2 months from the egg hatching to emergence), most spend at least a year and some much longer (5 years or more in places where the climate is arduous) as aquatic larvae. Most will spend at least one winter in your pond and have to suffer through any maintenance activities you perform. Some may not survive activities such as cleaning the "mulm" from your pond.

Emergence

Dragonfly and damselfly larvae are aquatic creatures. At the end of the final larval stage, the nymph climbs out into the air, perhaps onto a stone, or a plant stalk, or even some algae floating at the surface. Its position stabilized, the insect splits this last larval skin open along a suture on the back of the thorax and pulls itself out through this hole. The exact details of extraction vary with the orientation of the larval skin. Odonate development lacks the familiar pupal stage (e.g. chrysalis of a butterfly). By the time the larva leaves the water, an adult, albeit a rather uninflated one, exists inside the skin which is about to be shed.


a stream species tranforms on a vertical rock face
The empty larval case, called the exuvia, is hidden mainly in the shadow.
The crumpled features on the back of the thorax are the unexpanded wings.


After the insect has extracted itself, a period of time, usually a couple of hours or so, elapses during which the body and wings expand and cure sufficiently to withstand flight. Emergence is not an easy process, and the insect is incredibly vulnerable as it prepares for life in an entirely new medium. Many things can go wrong, and sometimes do. Weather changes can have disastrous results. Winds and rain can cause irreparable damage by bringing things into contact with the developing body or wings. The insects can become dislodged, falling into the water where they can drown or be eaten. Where suitable emergence sites are limited, larvae can walk over one another disrupting development. During emergence, the insect can't fly away, and hence is vulnerable to numerous predators. Emergence requires a lot of energy and some insects die trying.

damaged dragonfly

this dragonfly (Libellula quadrimaculata) had a very hard emergence
The front wings appear to be undamaged, but the back wing
on the left appears to have gotten folded over and the one
on the right appears to have been broken. The abdomen is
also malformed, having a segment which twists to the left.
(You probably won't see a picture like this in any books.)


The date and time that emergence takes place tends to be species related but can be affected by recent weather conditions (especially the temperature). The damselflies I am familiar with tend to emerge in the morning and fly in the early afternoon.

After curing sufficiently (perhaps a bit earlier if it is disturbed), the insect, now in its more familiar dragonfly or damselfly form, makes its maiden flight, away from the water. Compared to the mature adults you might be familiar with, insects which have just completed their emergence lack the vibrant colors (especially noticeable in the eyes). Their wings have a higher gloss, as though covered with cellophane/saran wrap and look more fragile. The maiden flight is generally short (more like a hop) and does not appear strong or well coordinated - the flight muscles are weak and the thoracic skeleton has not fully hardened. Recently emerged insects are often snapped up by hungry or nesting birds.

Most of the pond or quiet water species I am familiar with usually emerge on vegetation in or near the water. If you are lucky, you might see a nymph climbing out of the water. I usually find them after their transformation has started, usually long after. Emergence is a treat to watch, but make yourself comfortable, most things don't happen very quickly. Take pictures if you want, but try not to disturb the insect for it is tired and vulnerable. Also, take care of yourself, emergence seldom takes occurs in a convenient place.

You can monitor the production of your pond by collecting the empty larval skins, or exuviae, on a regular basis. Examine the emergent vegetation and other suitable substates like sticks and rocks. If you find an exuvia, check that it is empty. Whitish strands can usually be seen sticking out of the hole through which the insect got out. These strands are the remains of the old tracheal linings. Check that the insect has actually left the vegetation - it may just have moved up to catch more sunlight. Collect these empty skins by gently sliding them up the vegetation, or prying them off the substrate. Be careful, they are very light and easily carried away by any breeze. If the wind has been blowing you may find some of the empty skins in the water, but they can remain attached to the substrate for some time. Sorting these by appearance will give you an idea how many species are using your pond. (Remember that there are other kinds of insects that have an aquatic larval stage.) Record the numbers by date to give yourself an idea of the cycle of emergence. Probably you will not see some exuviae that are hidden or inaccessible, but this will give you some indication about what is there.

Maturation

Having emerged from the water and attained its aereal form, the resulting dragonfly or damselfly spends some time away from the water while it matures sexually. This period generally ranges from a few days to a couple of weeks, but can be longer in species that migrate. During this time, the body and wings harden, and the color becomes more vibrant. The males of some species undergo dramatic color changes during this period. This is also a period of high mortality. In cooler areas, individuals may be attracted to the warm surface of asphalt roads and killed or stunned by passing cars and trucks.

When they return to the water they are ready to mate.

Adult Behaviour

Adult odonata feed mainly on other insects such as small gnats, mosquitoes, black flies, horse flies, and deer flies. (Many a beleagured north woods hiker has expressed gratitude and encouragement to feeding dragonflies.) Some even feed on other dragonflies or damselflies. Most species hunt mainly during the day, but a few species are crepuscular (evening) hunters. I would not be surprised to find some daytime hunters regularly around bright lights in the evenings, but I personally don't know of this happening.

One interesting behavioral aspect that you can observe for dragonflies which perch regularly is their postures. Dragonflies can adjust their orientation, body position and wing positions to regulate their body temperature. Sometimes a dragonfly will position itself so that the tip of the abdomen is pointed at the sun and the wings are rotated down and tipped forward to shade the thorax. The surface of the body exposed directly to the sun is thus minimized. When the sun is high in sky, the dragonfly is almost standing on its head and this extreme position is called the "obelisk" posture. Why doesn't the dragonfly just move to a shady spot? If the insect cools too much, it only needs to adjust its wings or body. If it has moved it will need to move back, and this uses up energy.

Identification

Dragonflies and damselflies have numerous species specific requirements. The ones around your pond will usually have an aquatic stage that can tolerate the climatic conditions in your area and pond. There are a number of species that seem to prefer the acidic water conditions of bogs and fens. A number of species prefer the running water of streams, or rivers. A number of other species prefer ponds or slowly moving water. Many of these pond species can be identified from a distance, but it does take lots of practice. Field guides are available for some areas.

basking dragonfly

a common pond dragonfly in the southwest U.S., Libellula saturata, basking in the sun


The species of dragonflies that prefer ponds belong mainly to the family Libellulidae, often called skimmers in field guides. Many of these are territorial, hunting from favorite perches along the water. They can be quite active in the warmer weather. A number of these are brightly colored, the males and females sometimes looking considerably different. Many have conspicuous color markings on their wings. The libellulids are among the easiest dragonflies for the beginner to identify because of their coloration, and their perching habits, often right out in the open. The males tend to be more noticeable. (General insect guide books don't always distinguish between males and females in their pictures.)

Dragonflies can be quite tolerant of photographers, but it is generally a waste of time and energy to attempt to photograph a reluctant individual. One key area used in identification in the texts is the venation pattern of the wings. For libellulids, some veins in the rear wing form a characteristic boot-shaped pattern - toe down. For many non-libellulids, a picture or some idea of the species dependent appendages on the male may be necessary for a positive identification.

Unarguably the best dragonfly pictures currently on the web, these scanned dragonflies, while limited in number, can be used to examine wing venation and color patterns. Look these pictures up. There are a number of damselfly species that occur around ponds. Being smaller, these are harder to photograph reliably. The appendages on the male are the best characterisitics for identification, but the worst to try and photograph. Many of the species look similar, and may not be separable photographically without experience or a photographic reference collection. The patterns on the males and females often differ, so it helps if you can photograph the two together.

Unlike butterflies, there is little color or pattern variation between members of one species. The bright colors of dead specimens fade quickly unless they are properly preserved - even then they are not as brilliant as in life.

Conclusions

Dragonflies and damselflies are exciting creatures to study. Use your web pages to document the activity you observe. Anecdotal information seldom makes it into the literature, or is difficult to find. Wetlands, even small ones, are an important component of world around us.

further information and links

Disclaimer

This article is based on published material and personal experience. While I study dragonflies and damselflies whenever I can, I am an amateur entomologist (i.e. a person who studies insects) and a photographer, rather than an insect collector. Errors in presentation or interpretation are mine alone. Feel free to contact me if you have any problems with the text (corrections, clarifications, whatever). Thank you.

Ron Lyons (volunteer 1990-1999)
Chula Vista Nature Center, 1000 Gunpowder Point Drive, Chula Vista, CA 91910-1201