Evolutionary Perfection
Somethings do get better with age. Evolution has been very kind to the Odonata order of insects. The Odonata order has hundreds of millions of years of darwinian evolution behind it. In fact, the earliest fossil records of the dragonfly go back to the Upper Carboniferous period approximately 325 million years ago. The fossil record of Odonata reveals much to us.
The fossils of Protodonata (Megaanisoptera Namurian) species are much larger than the modern day dragonflies. The Protodonata dragonflies had wingspans up to 70cm (28 inches). Over time, the dragonfly has gotten smaller. Today’s dragonfly has a wingspan between 3-9 cm in length. Researchers believe the larger dragonfly lived in an oxygen rich environment. In fact, new experiments have confirmed that raising dragonflies in an oxygen rich environment will grow bigger dragonflies, a phenomenon known as hyperoxia. As oxygen levels decreased, from its peaks in upper carboniferous period, the dragonfly evolved into a smaller version of it’s modern self. Moreover some researchers believe, once birds arrived on the scene, insects made themselves small in an effort to hide from the birds.
Classification
Today, there are approximately 5,000 species of Odonata globally and about 400 in America. The current Odonata order can be classified into two suborders, Anisopetera (dragonfly) and Zygopetera (damselfly).
Anisoptera is derived from the Greek word ‘anisos’, meaning “unequal” and ‘pteron’, meaning “wing”. Since it’s hindwing is broader at the base than its forewings. This is why the Greeks called it Anisopetera, an unequaled winged insect.
Insects belonging to the sub-oder Zygopetera (or Damselflies), have narrower wings that are of similar size and shape. At rest, the damselfly’s wings are held closely together, and may appear as only two wings.
Over time, the Odonata order has developed many unique adaptations - such as a neurologically enhanced flight-dynamics system, compound 360 degree eyesight and an extendible hinged jaw. We will look at these topics in more detail below.
Art Imitating Life
Art imitating life is no secret to Hollywood screenwriters. In the 1979 science fiction film ‘Alien’, which was directed by Ridley Scott, an alien life form is found on the mining spaceship - the Nostromo. The movie is set in the future, somewhere between the years 2093 and 2193.
The Swiss artist H. R. Giger designed the (Xenomorph) alien creature in the movie. The alien’s arm-like projecting jaws were inspired by the dragonfly nymph. The dragonfly nymph has extendible, hinged jaws that project outward.
It does make me wonder. Considering the evolutionary success of the dragonfly, what might a dragonfly look like in 300+ million years into the future. Might it be space bound like the Xenomorph? I do know this, the Dragonfly has a much better chance of surviving another 300 million years than humankind. Well lets hope we are still around to see what happens.
There is a famous quote in the movie, regarding the Xenomorph alien:
“You still don't understand what you're dealing with, do you? Perfect organism. Its structural perfection is matched only by its hostility. I admire its purity. A survivor." ―Ash.
This same quote could be applied to Odonata, as it is the ultimate survivor with a 325 million year track record of survival. Not too shabby!
The Perfect Predator
Which of earth’s predators is the most successful in capturing its prey? Surely the world’s most successful predator must be an apex predator. In the arctic tundra it must be the polar bear. In the African savanna is it the lion or is it the cheetah? Perhaps it is humans! To answer these questions, let us take a look at the kill rates for some of the world’s most famous predators:
Tigers 5%
Polar Bear 10%
Wolves 14%
Lions 25%
Domestic cat 32%
Hyenas 33%
Leopards 38%
Cheetah 58%
African Wild Dogs 85%
Dragonfly 95%
I suppose you should not be shocked to learn that it is an Arthropod, or an insect. After all, insects are some of the most successful species on the planet. Moreover, the insect with the highest success rate of capturing it’s prey also happens to be one of the oldest living species on the planet. The dragonfly is one of nature’s most successful predators - the perfect predator.
Dragonflies are predatory insects while in the nymph and adult stages of life. They are voracious carnivores and prefer feeding on living-prey. Moreover, Dragonflies predict and plan their hunts. Dragonflies that catch prey in mid-air, may remain in flight while devouring it.
Moreover as a predator Odonata can attack its prey in two modes:
◆ by stalking it, or trailing behind it in a NASCAR drafting style
◆ Or by intercepting its prey at a fixed point in space. To accomplish this, the dragonfly must calculate its own position and the position of its prey in realtime.
Extraordinary Vision
No other insect has the visual acuity of a dragonfly. The dragonflies massive globular eyes are really something to behold. These compound eyes are beautiful adaptations and are iridescent in color. The metallic colors are an excellent example of the phenomenon in physics called the Quantum Electro-dynamic Effect (QED).
360 Degrees Of Vision
An adult dragonfly has a compound vision system with over 24,000 ommatidia (facets) in each eye, or more than 48,000 sensors in total. The visual field of view is almost 360 degrees. Moreover the dragonfly also has smaller single eyes too. The extraordinary combination of flight and sight make dragonflies apex predators.
New Colors in the Rainbow
The compound eyes functions in four ways and it can detect color, UV light, polarization and movement. More importantly Dragonflies are not limited to trichromatic vision ( red, green, blue) like humans. In the case of Dragonflies some species have between 11 and 30 different levels of chromatic vision (opsins). What does this all mean? Dragonflies have Super Ultra HD eyes and see a rainbow much differently that humans do.
Drone Makers Please Pay Attention
The dragonflies visual acuity is something that researchers all over the world are studying. Scientists are trying to develop computer based vision systems that mimic the dragonflies visual system. Moreover, drone researchers are also using dragonflies as a model for creating next-generation drones that can catch other drones in mid-air.
Japanese Haiku
This Japanese haiku poem, by Chinsoku, summarizes the dragonfly best:
The face of the dragonfly
Is practically nothing
But eyes!
Acrobatic Flyers
Dragonflies are strong fliers and can range for many miles. Dragonflies are the best fliers that the planet earth has ever produced. They are highly agile predators due to their wing biomechanics. They capture their prey in mid air, using highly complex, three dimensional flight behaviors. Not many other species can command the skies like Odonata. Even a Hummingbird, another gifted aerial performer, can not perform the feats of Odonata. A hummingbird has only two wings and a Dragonfly has four wings.
Aerial 4-wheel drive
Much of Odonata’s flight dynamics boils down to an aerial version of 4-wheel drive. Odonata has four wings and the wings operate independently of one another. Their precision flight maneuvers are based on their abilities to modulate their wing’s phase, beat frequency and loading. This wing capability allows Odonata to fly in 6 different directions: up/down, left/right, forward/backward as well as the various permutations.
Wing Corrugation is Key
The shape of the dragonfly’s wing plays a critical role in its flight performance. Its wings are not flat, but are are corrugated. In a two dimensional cross section of their wings, we can see peaks and valleys of corrugation. Each peak and valley creates a vortex which is used to aerodynamically enhance their flight.
The Larva
The Dragonfly larva is distinctively recognizable due to its unique morphological features, specifically is prehensile and extensible labium (mouth). There is significant diversity of form and behavior associated with each species of Odonata in the larva stage. Odonata larvae are aquatic creatures and breathe under water.
Respiratory-Propulsion
Odonata larva have highly developed and specialized respiratory system. The larva take in oxygen and release CO2 and this process is called respiration. Moreover the Odonata larvae use their anus to ventilate which facilitates respiration.The larva posses specialized organs that support respiration and its gills are found in their abdomen. There are two main systems of gills - the simplex and duplex gills. Essentially the rectum acts as a trachea. More importantly the nymph’s rectum also intakes water and then expels the water through it anus. The water serves as a means of jet propulsion or locomotion.
An Under Water Predator
Odonata Larvae are predaceous carnivores. Their distinct piercers and extensible labium enable them to capture prey at a distance, chew and then swallow them. Prey is mainly detected by movement and are caught and eaten alive. Nymphs can extend their jaws up to 1/3 the length of their body. The Odonata larvae remain cryptic and motionless waiting for their prey to move within their striking distance. The foraging strategy is essentially an ambush or attack mode.
Night Stalkers
Many Odonata species stay inactive during the daytime in order to remain hidden from other predators. While most of their foraging and hunting is supported by vision from motion detection, dragonfly larvae also have the ability to function using mechanoreceptors. These mechanoreceptors allow them to hunt in the dawn, dusk, and night time using vibration. Some dragonfly larvae also use chemoreceptors for foraging and hunting.
Ascension
Odonata live in two different worlds during it’s life time. They begin life under water and as adults then ascend into the air.
Growth of the Nymph
There are number of molting events during the lifetime of a dragonfly’s time as a nymph in the water. Depending on the type of dragonfly, the number of molting events range from 9-17, or an average of 12 molts. The Dragonfly’s final molt from the larvae stage results in the emergence of a fully formed adult dragonfly.
Between molting stages, the body of the Dragonfly grows, this difference in growth is called the growth rate. There is variation in the growth rate between one stage and the next, as well as a difference in body parts, I.E., the growth rate of a head verse dorsal. Growth rates are a function of species, environment, and seasonal regulations.
Metamorphosis
Metamorphosis is the irreversible changes in the morphology of the nymph into a dragonfly. This morphology is controlled by the endocrine system and begins with the decrease in juvenile hormones and increase in ecdysone. The onset of metamorphosis can be detected by changes in the thoracic muscles, the dorsal extent and the pigment in the compound eyes.
Emergence
Depending on the species of Dragonfly the emergence process can take, between 30 minutes to 1.5 hours to complete. Weather effects the duration of the emergence. Emergence takes place from May through the end of August in New England.
There are four stages of emergence, they are:
Stage 1:Nymphs leave the water by climbing up plants nearer to the shore, and in shallow water. The dragonfly nymph is completely out of the water and are encased in an exuviae.
Stage 2: The exuviae cuticle begins to split open by the thorax
Stage 3: the abdomen is withdrawn from the exuviae
Stage 4: Wings are extracted, pumped up, fully extended and are ready for flight
The Zuni People and Dragonflies
The concept of metamorphosis and emergence is ancient. It can be found in many of the Native American spirits, myths and folklore throughout the southwest. On a prehistoric bowl, from the Zuni reservation, a humped back figure playing a flute appears as an insect. Zuni people believe this insect led the pueblo-based people’s mythological emergence from the underworld onto the surface of the earth. Did the dragonfly’s emergence inspire this story into Zuni culture and spirituality?
The Adult
We are very fortunate that Odonata is one of the most studied insects in the world. There is much that we know about it’s ecology and behavior of these insects. Yet there is so much more to learn.
The Maturation Phase
Known as the phase of the adult dragonfly’s life, that precedes the onset of reproductive maturity. This phase denotes sexual immaturity and the inability to reproduce. The duration of this phase varies based on species, and the environment that the species is found in. The approximate duration of the maturation phase ranges from 13-15 days to 6- 7 months.
The Mature Dragonfly
The adult Dragonfly spends the majority of it’s adult life hunting, and reproducing. While hunting or foraging the adult dragonfly has special modes or styles. These styles range from mid-air hunting, perching mode, and a gleaning mode. Moreover, much is know about how Odonata handles its prey once captured, subdued as well as processing it. Odonata feed primarily on mosquitos and midges and helps keep them under control. A misperception is that dragonflies sting, they don’t, but they may ‘pinch’ if mishandled.
Reproduction
Odonata’s reproductive behaviors are also well documented. Much has been written about how a male and a female encounter each other. Moreover, during reproduction there is the notion of territory. The males will stake out a territory which it will defend from other males. During this time male dragonflies become aggressive and will patrol their territory. Moreover they use their visual system for communication and recognition to discern male-to-male and male-to-female encounters. Pre and post copulation is also very well document in the literature. Male dragonflies have multiple sex organs.
Learn More
Dragonflies are fascinating creatures. We have only touched upon some of the highlights of these amazing insects. I encourage you to learn more about Dragonflies. As previously mentioned, there is an abundance of literature on dragonflies. For example, here are some additional topics worth researching on you own:
Dragon flies can thermoregulate their body temperature.
Some dragonflies migrate
Dragonflies and People
As mentioned above, dragonflies are often the main topic in Japanese Haiku poetry. In addition, The Zuni Indians of the southwest have made references to dragonflies. As we can see dragonflies and people have been interacting for centuries.
However, traditional perceptions about dragonflies vary. In European cultures, dragonflies are often perceived as threatening. Whereas, in Asian culture the dragonfly symbolizes courage, strength, victory and happiness.
Dragonflies in China are used for medicinal or magical purposes, such as:
A remedy for cooling
To stimulate erection, or delay ejaculation
Heads taken off dragonflies on the fifth day, of the fifth moon and buried inside the home can change into azure pearls.
In ancient times, in Mesopotamia, dragonflies eggs were used medicinally as a cure for menstrual pains. Their eggs were also used as ingredients in antidotes.
What Can You Do To Help?
Dragonfly biotopes are disappearing at an alarming rate. Anthropogenic impacts vary across the globe, the nation and at the local level. Much of this has to do with rising human population density.
You can help by protecting existing dragonfly biotopes and by creating new biotopes. The Japanese have been very successful in creating new biotopes that support dragonflies in urban areas. Start today by creating a dragonfly pond or garden in your neighborhood, or backyard.
Without insects, the world as we know it would cease to exist. We must not wait for conditions to worsen and for dragonfly biotopes to be destroyed on a global scale. I do believe the dragonfly is a keystone insect, it acts as an ‘equalizer’ and is constantly working to keep nature in balance. It is truly a survivor, and the prefect predator.
Also leave a comment below.