🪰 Order Odonata

Odonata includes some of the most beautiful and efficient predatory insects in the field, especially dragonflies and damselflies. Their large eyes, net-veined wings, aerial hunting ability, and aquatic naiads make them easy to recognize and agriculturally useful as natural enemies.

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Meaning and General Characters of Odonata

• Odon means tooth
• Common representatives are dragonflies and damselflies

Important characters of the order:

• medium to large, attractively coloured insects
• head globular and constricted behind into a petiolate neck
• compound eyes very large
• three ocelli present
• mouthparts adapted for biting; mandibles strongly toothed
• wings equal or subequal, membranous, with net-like venation and many cross veins
• a dark pterostigma near the costal apex
• subcosta ends at nodus
• no wing-flexing mechanism
• legs placed anteroventrally and adapted for grasping prey
• abdomen long and slender
• development hemimetabolous, with aquatic naiad stage

Male odonates show a special reproductive feature: the gonopore lies on the ninth abdominal segment, but the functional copulatory organ is on the second abdominal sternite. Transfer of sperm before mating is called intra-male sperm translocation.

Large compound eyes, net-veined membranous wings with pterostigma, predatory legs, and aquatic naiads are key identifying features of Odonata.

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Importance of Odonata

Adults are active aerial predators and can catch prey in flight. Naiads are also predatory and live in fresh water.

Because both stages are predaceous, dragonflies and damselflies are ecologically important and often beneficial in agro-ecosystems.

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Anisoptera and Zygoptera Compared

Odonata is divided into two suborders:

1. Anisoptera - dragonflies
2. Zygoptera - damselflies

Adult characters

Character	Anisoptera (Dragonflies)	Zygoptera (Damselflies)
Flight	Strong fliers	Weak fliers
Wings	Hindwings broader basally than forewings	Wings equal
Wing attachment	Wings broadly attached	Wings petiolated and narrowly attached
Wing venation	Forewings and hindwings differ	Venation similar in both wings
Resting position	Wings spread laterally at rest	Wings held above abdomen
Eyes	Large and meeting dorsally (holoptic)	Wide apart (dichoptic)
Male terminal appendages	Three terminal appendages: two superior cerci and one inferior appendage (epiproct)	Four terminal appendages: superior cerci plus inferior appendages (paraprocts)
Oviposition	Exophytic	Endophytic

Naiad characters

Character	Anisopteran naiad	Zygopteran naiad
Body form	Stout and robust	Slender and fragile
Gills	Internal, associated with rectum	Three external caudal gills
Movement	Jet propulsion by forceful expulsion of water through anus	No jet propulsion

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Summary Cheat Sheet

• Odonata includes dragonflies and damselflies.
• Important order features are large eyes, biting mouthparts, net-veined membranous wings, pterostigma, predatory legs, and aquatic naiads.
• Development is hemimetabolous.
• Adults and naiads are both predatory, so Odonata is generally beneficial.
• Anisoptera are strong fliers with broader hindwings and eyes meeting dorsally.
• Zygoptera are weaker fliers with similar wings and eyes widely separated.
• Anisopteran naiads have internal rectal gills and jet propulsion, while zygopteran naiads have external caudal gills.

References

2 sources • [1] [2]

[1]

Fundamentals of Entomology

[2]

Insect Morphology and Systematics