Week One
Lesson 1: Life Cycle of Dragonflies
S2L1. Obtain, evaluate, and communicate information about the life cycles of living organisms.
What are Dragonflies?
- Dragonflies are predatory insects, and have been around for almost 300 million years. They have 2 pairs of large transparent wings, with long and sometimes colorful bodies. Its scientific name is Anisoptera. Dragonflies thrive in freshwater, and they like to live in warmer climates.
Why are they important? What do they do?
- They are important to the environment as predators and prey. This insect needs clean water and good oxygen levels, so some scientists consider dragonflies bioindicators. It helps indicate the health of an ecosystem.
- Dragonflies help the environment as well. It allows people like gardeners to not use harmful substances like pesticides.
- One dragonfly can eat hundreds of mosquitoes, flies and ants in one day!
What is a dragonfly's life like?
- Dragonflies live up to about 6 months.
- The stages in the life cycle:
- Eggs
- Larva/Nymph
- Adult Dragonfly
- The length of these stages can also depend on the species of dragonfly.
The Egg Stage
- A female chooses an adequate habitat with still water to lay her eggs. The eggs are laid on aquatic plants or mud banks that are submerged in water, or sometime even directly in the water.
- A female dragonfly can lay hundreds to thousands of eggs in a lifespan.
- The region, such as tropical or temperate, can determine how long the eggs take to hatch. Tropical regions: minimum of 5 days Temperate: would most likely hatch the following spring.
- Georgia has a more subtropical climate, indicating that dragonfly eggs are more likely to hatch faster.
The Nymph Stage
- Dragonfly nymphs look nothing like their adult forms.
- They "molt" meaning that they can shed their skin, multiple times depending on the species.
- Tropical region: less part of lifespan as nymphs
- Temperate region: longer part of lifespan as nymphs
- These nymphs are aquatic, and they thrive in marshes and ponds until molting for the last time. Being hemimetabolous, the nymph does not cocoon before turning into an adult. Their skin simply splits, and the adult dragonfly emerges.
The Adult Stage
- After emerging from a nymph, dragonflies spend the next month to fully mature.
- These insects are voracious predators, and eat other small insects such as mosquitoes and flies.
- Dragonflies have the ability to catch/feed while flying, and are able to fly backwards, forwards, sideways and hover.
- A fully developed female dragonfly can mate several times before laying eggs. They spend 2 to 4 months as adults before dying.
Here is a quick video for a simple visual of a dragonfly's life cycle:
Dragonflies are great hunters:
- Dragonflies are carnivores, and they like to eat mosquitoes and gnats. They'll even eat cicadas, flies and other smaller dragonflies.
- To catch prey, they create a basket with their legs and swoop in on their prey, biting it to keep it captured. They can eat what they catch while flying!
- A dragonflies sight is incredible. To look out for predators as well as prey, they have two large compound eyes made up of thousands of other tiny eyes to enable themselves to see in all directions.
- But dragonflies also have their own enemies. Some of their predators include ducks, fish, birds and water beetles.
Species:
- There are about 7,000 species of dragonfly species around today.
- In 2009, 10% of dragonfly species were threatened by extinction.
- Some species in Georgia include:
- Blue dasher
- Widow skimmer
- Slaty skimmer
- Eastern pond hawk
- Wandering glider
- Common whitetail
- Great blue skimmer
- Eastern amberwing
- The Chattooga River, forming part of the border between Georgia and South Carolina, is home to around 34 Anisoptera species as well as 11 Zygoptera species. (Anisoptera: Dragonfly) (Zygoptera: Damselfly)
Other fun facts!
- Dragonflies generally do not sting or bite people. They are harmless to us.
- Prehistoric dragonflies had wings that could span up to 2 feet!
- Groups of dragonflies are called flights or clusters.
- These insects are invertebrates.
- Watching dragonflies is called "oding". Although it may seem strange, it is similar to birdwatching.
- They can reach speeds up to 35 miles an hour in flight.
Comments