DRAGONFLIES AND BUTTERFLIES: HOW ARE THEY DIFFERENT?

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Both dragonflies and butterflies belong to the kingdom Animalia, phylum Arthropoda, and class Insecta.  Insects are the most numerous animals

on earth.    Insects share several characteristics, which include the exoskeleton; a segmented body containing jointed appendages, and wings.

 There are three parts to the body of an insect: the head, the thorax and the abdomen.  Although dragonflies and butterflies share these

characteristics, they are very much from two different orders.  Dragonflies are of the order Odonata while butterflies are in the order of

Lepidoptera.  What occurred to make these two insects evolve into two different orders? 
   
The evolution of insects occurred in four stages (Kendall, 2005).  Apterygote stage is the first stage of the evolutionary process.  These insects

were very simple organisms with no wings, no developed legs, or body parts.  They first appeared in the Devonian period approximately 380

million years ago following the development of vascular seedless plants.  Silverfish closely resemble these ancient insects.  They do not have a

metamorphosis; instead they have an ametabolous development.  Ametabolous development means that the immature greatly resemble the

adult except for the presence of genitalia and gonads.  The fossils from this period  (mid-Devonian) already show the specialized features of the

 insect order.

The second stage, known as the Paleoptera stage, involves the formation of wings on the insects. These wings where held straight out or straight back.  They were also long and rigid. This was a very important step in the evolutionary process of insects.  Developing wings allowed them to do several things.  Insects could now fly great distances and therefore disperse plant life, travel to locate new sources of food, find mates, and escape predators.  Along with the development of the wings came a new more complex type of metamorphosis, the hemimetabolous development.  The hemimetabolous development is an incomplete metamorphosis, which means that some change will take place.  In this process, the egg is deposited into the water where it develops into a nymph.  The nymph resembles the adult, but there is not a pupa stage: however, the nymph will go through several molts before actually becoming an adult.  It is here at this stage that we find the first fossilized remains of a dragonfly.  It dates back to the late Carboniferous period about 300 million years ago and it was in the order of Paleodictyoptera, which is the precursor of the order Odonata.    

Neopterous stage is the third stage in the evolutionary process of the insect.  Neopterous means "new wing."  This new wing could now be folded back over the insect's abdomen through a new addition known as a flexon that allowed the wing to bend at the base.  This allowed insects to crawl into smaller spaces to find food.  These insects maintained a hemimetabolous development, which can be seen today in crickets, cockroaches, and grasshoppers.

The final stage of the insect evolution is the holometabolous development or a complete metamorphosis.  A group of neopterous insects developed this new form of metamorphosis.  This development shows that the larval and the adult form are completely different from one another.  An example of this process is the butterfly.

The dragonfly, according to fossil evidence appeared first in the evolutionary process and therefore its life cycle reflects the hemimetabolous development.  As shown in the dragonfly life cycle below, the egg is laid in or near water, usually on a floating plant.

Dragonfly Life Cycle

                       

                        Figure 1: http://www.kidfish.bc.ca/images/dragonfly_life_cycle.jpg

The egg can take anywhere from 7 days to several months to hatch.  Once the egg hatches, the dragonfly will spend most of its life in the larval stage (nymph) underneath the surface of the water using gills to breathe and feasting on both vertebrates (tadpoles and fish) and other invertebrates.  The larval stage can last anywhere between 3 months and 10 years depending upon the species.  During this time, the larvae can go through approximately 10 to 20 molts.  The final stage in the cycle takes place on a fixed object usually a plant some distance from the water.  The dragonfly can live as long as four months in the adult stage.

Looking at the life cycle of the butterfly life cycle (Figure 2), one sees a more involved and evolved process.  Like the dragonfly, the butterfly begins life as an egg but not laid on a plant found in water but rather on a leaf.  When the egg hatches, caterpillar                                                      

                                            Butterfly Life Cycle

                                   


(Larvae) is born.  The caterpillar immediately begins eating the leaves and the flowers around it.  Just like the dragonfly, the caterpillar will also go through many molts during this stage of its cycle.  By the time the caterpillar is ready to pupate, it will have increased in size up to a thousand times.  When the caterpillar is ready, it will form the chrysalis or pupa where it will rest and transform into the final stage of adulthood – a butterfly.  The average lifespan of an adult butterfly can range from 20 to 40 days; others may live up to six months. 

Butterflies and dragonflies differ not only in life cycle but they also differ in choice of habitat, diet and morphology.  Butterflies can be found in various environments: from rainforests to deciduous forests and from wetlands to farmlands.  They also are known to migrate in order to avoid adverse weather or environments (enchantedlearning.com, 2006).  Some butterflies like the Monarch migrate thousands of miles while others like the Painted Lady migrate very short distances.  Dragonflies like to be around moist areas such as wetlands, ponds, streams, and lakes.  They live most of their lives as nymphs in the water and will return there as adults to mate and lay their eggs.  As for their diet, butterflies will uncoil their proboscis (tongue) and drink the nectar from flowers where the dragonfly much prefers flying insects like bees and unfortunately butterflies for their meals.  Morphologically speaking, dragonflies and butterflies share some general characteristics.  Both have three bodily segments: head, thorax and abdomen.  Both have compound eyes, wings, and six legs, but there is where the similarities end.


Figure 3




Figure 4

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Dragonflies and butterflies possess two pair of wings.  The butterfly's wings are made up of two large pairs of wings each possessing a forewing and a hindwing. 

Their wings are scaly to produce the color, and are attached to the thorax.  The veins in the wings nourish them with blood.  Butterflies can’t fly if the temperature of

their body falls below 85 degrees and therefore need to sun themselves in order to warm up.  Some butterflies can fly up to 30 miles per hour.  Butterflies also have

a pair of antennae with small receptors attached for smelling.  Dragonflies have two pairs of wings that are transparent, rigid, straight, and have few veins.  They do

not fold or bend, but this does not affect their flying ability.  Unlike butterflies, dragonflies are adept at flying.  They can reach speeds up to 90 miles per hour as

well as having the ability to fly sideways, backwards, hover, turn at right angles and of course fly straight (Ingram, 2000). Dragonflies also have jaws to catch and

eat insects where the butterfly has a proboscis to drink nectar.  The appendages attached at the bottom of the abdomen are used for holding and mating. 

Although butterflies and dragonflies show some similarities in structure and development, they are of a totally different order.  Each has developed in a unique manner to fit the niche in which it occupies.  Butterflies help to pollinate flowers and are food for the dragonflies.  Dragonflies are ancient insects that have withstood the test of time and change.  Both make the world a little more beautiful and special.

 

Kathleen Tait

Environmental Science

 

 

 

 

 

 

 

 

 

 

 

 

                                                            CITATIONS

 

Butterflies. Retrieved August 12, 2006, from Kids' Planet: Defenders of Wildlife Web site: http://www.kidsplanet.org/factsheets/butterflies.html

Evolution and Ancestors.  Retrieved August 1, 2006, from Dragonflies – Living Fossils Web site: http://skurvits.tripods.com/dragonflieslivingfossils/index.html

Ingram, Jay (August 29,2000). Dragonfly’s evolution of flight. Retrieved August 1, 2006, from Discovery Channel Website: http://www.exn.ca/Templates/printstory.asp?PageName=Discovery&story_id=2000081857

Insects Life Cycles. Retrieved August 18, 2006, from Earth-Life Web Productions Web site: http://www.earthlife.net/insects/lifecycles.html

Kendall, David (2005). Insect Life Cycles. Retrieved August 10, 2006, from Kendall Bioresearch Services Web site: http://www.kendall-bioresearch.co.uk/life.htm

Using Live Insects. Retrieved August 13,2006, from Center for Insect Science Education Outreach Web site: http://insected.arizona.edu

 (1996-2006). What is a Butterfly?. Retrieved August 15, 2006, from Enchanted Learning http://www.enchantedlearning.com/subjects/butterfly/