[Biology Class Notes] on Dragonfly Life Cycle Pdf

Introduction to Dragonfly

The dragonfly is a large, colorful, predatory insect that is found generally in or near watery. Over 5,000 known species of dragonflies exist, and fossil evidence suggests that they have been on earth for many years.

A dragonfly is an insect of the order Odonata, Anisoptera infraorder. They have long, thin, colorful bodies, six legs, large eyes, and two pairs of transparent wings that enable them to propel upward, downward, forward, backward and side – to – side while in flight. They are skilled flyers, and tend only to catch prey and eat while flying.

 They come in a variety of colors and are considered mainly beneficial due to their ability to combat other nuisance bugs such as mosquitos, termites, gnats, flies and other flying insects in the population.

Dragonfly Life Cycle Stages

All species of dragonflies have three stages in their life cycle. The embryo, the larva (or nymph), and an adult.

Egg

The dragonfly starts life, like an egg, in or near water. The female dragonfly will often lay her eggs after mating while still holding on to the male, or while the male is guarding her against predators and other males. She will never lay her eggs alone.

 Normally, the eggs are dropped directly into the water, on or inside aquatic plants or in the humid ground near the water.

Depending on the species they will typically hatch in one to five weeks. A female in her lifetime can lay several thousand eggs, usually over a few days or weeks in several different batches.

Nymph 

Tiny creatures with six legs, wing-sheaths, hinged jaws and the ability to breathe when underwater will emerge from the eggs after the incubation period. This is the dragonfly’s longest life stage, and it is important to note here that dragonflies spend most of their lives underwater because of this. 

Typically, these larvae will also molt, or shed their skin within a few hours to make way for new growth.

They will also molt to reach full growth as often as necessary, sometimes molting as many as 14 times. Depending on the species and environment, larval development can last anywhere between two months, up to one or two years.

Whether the eggs are laid in cool water where food is scarce, or in an area where the climate is warm and food is abundant, development can be accelerated or slowed down resulting in the possibility of more than one generation per year in certain areas.

Adult 

Adulthood is triggered by a major dragonfly event, one which is called Emergence. Unlike butterflies, do not have a coconut stage in the life of a dragonfly and emerge as an adult through a final molting stage outside the water. 

The larva which is in the final stages will gather for several days near the edge of the water preparing for this final molt and at this time will begin to learn to breathe air. The trigger for this occurrence is the length of the day and the temperature, and can vary between species. 

The dragonfly larva will fly once ready to find vegetation on which to prepare to emerge as an adult. Some may travel up to several meters over dry land to find a suitable area with sufficient support to keep them safe during their final molt into adulthood. 

Once this perfect place is found, they start the emerging process by redistributing the fluids in their body first. This is no small feat, and requires them to slowly push their newly developed body out of their larval self ‘s old shell, leaving enough time between each portion to dry and harden enough for the new body to move forward. This process can take 1 to 3 hours and leaves behind a cast shell of their former selves, called an exuvia.

Newly emerging dragoons are usually very pale in color, and have reflective wings. During this time, they will hunt and prey on other flying insects as frequently as possible, and will spend about a week hunting far from the surface in preparation for maturity.

Dragonfly Life Cycle Facts

Stages of the dragonfly life cycle includes incomplete metamorphosis where the cocoon stage is not observed.

The free-crawling aquatic larva molds once after the egg is hatched and then begins to hunt voraciously. 

This will molt as the larva grows numerous times. The majority of larvae reach maturity within 1 to 3 years

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