Insectmag

INSECT insect.com/magazine

DECEMBER 2014

ALL THINGS

odonata

CONTENTS the odonata p. 4 key words p. 12 spot the differences p. 14 quiz p. 16

The Odonata O

donata, meaning the “toothed ones”, are the order of dragonflies and damselflies. Odonata are easy to spot because of their morphology. All of Odonata’s morphology makes them extreme hunters. They have very large compound eyes, small antennae, and strong visible mouthparts. Attached to their thorax they have three pairs of legs and two pairs of very large wings. Their segmented abdomen is very large compared the the rest of their body which helps it stabilize it while it flies.

Odonata can even fly backwards!

Dragonflies were some of the first winged insects to evolve, some 300 million years ago.

Modern dragonflies have wingspans of only two to five inches, but fossil dragonflies have been found with wingspans of up to two feet.

-Smithsonian

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Dragonflies and damselflies are sub orders that belong to the order Odonata. These sub orders are called Anisoptera for the dragonfly and Zygoptera for the damselflies. While they are very similar looking, there are some distinct differences that can help you distinguish between the two. At a resting state, the DECEMBER 2014 Odonata 5

dragonfly will keep its wings extended out while the damselflies will fold them backward. The damselflies eyes are located on the sides of its head. And while the dragonflies eyes are also located on the sides, they are often so large that they touch at the top. The dragonflies eggs are rounder and larger than the damselfies which are longer and smaller.

Odonata are hemimetabolous. This means that they undergo incomplete metamorphosis beginning with a fertilized egg a nymph hatches and emerges as an immature form.

The nymph then goes through a series of molts where it then grows into its adult form.

Odonata reproduction takes place near ponds and lakes because the female must deposit her eggs into water. A male and a female mate by forming a mating wheel where the male grips the female with his legs and inserts his seminal vesicle into her ovipositor which brings in his sperm. Once she is 6 INSECT MAGAZINE

DECEMBER 2014 Odonata 7

“The nymph then goes through a series of molts where it then grows into its adult form.”

inseminated, many males will guard her until she is ready to deposit the eggs into water.

This ensures that his sperm is secure from other males which may try and mate with the female.

In their larval stage, which can last up to two years, dragonflies are aquatic and eat just about anything—tadpoles, mosquitoes, fish, other insect larvae and even each other.

-Smithsonian

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The nymph stage can last from one to five years. As nymphs Odonata are fierce predators. They already show characteristics of their adult form with large eyes. They use their antennae to catch prey and are very agile in the water. Both dragonfly and damselfly nymphs have gills so they can breath underwater. But the damselflies gills are fin like and protrude from the end of the abdomen while dragonfly gills are on the sides of the abdomen. The nymphs molt underwater by expanding and contracting their lymph fluid to emerge out of their old exoskeleton.

Odonata nymphs molt six to fifteen times while in this stage. The nymph stage is where the Odonata lives most of its life. Once ready the nymph will crawl out of the water and find a safe resting spot to make its final molt. The nymph waits for its exoskeleton to dry and then begins its final molt where it emerges as its adult form.

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The adult form of the Odonata is what you are probably most familiar with. With its large eyes, beautiful elongated wings, and long abdomen they are a very distinct insect.

In the insect world they are predators but they have predators as well. Odonata are eaten by many amphibians, birds, and even other larger Odonata. They are generalists meaning they will eat whatever prey is available (they are not picky eaters) but mainly eat small insects. The abundance of the Odonata is an indicator of a healthy ecosystem because they signify that there is enough species diversity and good water quality.

Dragonflies, which eat insects as adults, are a great control on the mosquito population. A single dragonfly can eat 30 to hundreds of mosquitoes per day.

-Smithsonian

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key words: Morphology

The morphology of insects is the study and description of the form and structure of insects

Thorax

The thorax is the midsection (tagma) of the insect body

Segmented abdomen

The segmented abdomen is the largest tagma of the insect.

Compound eyes

Insect eyes made up of multiple parts.

Anisoptera

The scientific name for the dragonfly family.

Zygoptera

Moult

Hemimetabolous

Generalists

The scientific name for the damselfly family.

Incomplete metamorphosis consisting of egg, nymph, and adult stages.

The shedding of the insects exoskeleton to allow it to grow.

Omnivorous insects that eat whatever is available.

Nymph

The immature stage of hemimatabolous metamorphosis.

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dragonfly

dragonfly

dragonfly

dragonfly

damselfly

damselfly

damselfly

damselfly

spot the differences dragonfly

dragonfly

damselfly

damselfly

dragonfly

dragonfly

damselfly

damselfly

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dragonfly

dragonfly

damselfly

damselfly

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QUIZ 16 INSECT MAGAZINE

1. All of Odonata’s morphology makes them extreme scavengers.

true false

2. Odonata can even fly backwards.

true false

3. Hemimetabolous means that they undergo incomplete metamorphosis beginning with a fertilized egg a nymph hatches and emerges as an immature form.

true false

4. The nymph stage lasts two days.

true false

5. Nymphs must go to the surface to breath oxygen.

true false

6. “Generalists” means they will eat whatever prey is available

true false

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