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Common green darner: the dragonfly that hunts on the wing and sometimes migrates
The common green darner (Anax junius) is a large-eyed, large-bodied dragonfly of the darner family, common in the Pacific Northwest and much of North America. This profile comes from the National Park Service’s monthly "Featured Creature" series, October 2022 edition, for parks of the Klamath Inventory and Monitoring Network in southern Oregon and northern California.
Recognizing it
Adults have long abdomens (68 to 78 mm; 2.6 to 3 in) and a wingspan of 9 to 10 cm (3.5 to 4 in). A greenish-olive head with big eyes and a solid green thorax help identify them. The male’s black abdomen carries bright blue markings; the female’s is duller and more brownish-orange, though her color varies a lot and can approach his bright blue. The larvae are wingless aquatic animals with small wing pads that grow with each molt and a streamlined body.
Dragonflies and damselflies make up the insect order Odonata, named for toothlike ridges on the jaws. Damselflies are smaller and more slender and, with some exceptions, rest with their wings held vertically.
Water, prey and flight
Dragonflies need water to reproduce, so in summer the green darner is found around warm, still water: lakes, ponds, wetlands, marshes and slow backwaters. Non-breeding darners forage anywhere they find prey, including dry areas and outside North America.
Green darners are "hawkers," taking tiny flies, leafhoppers, beetles and even smaller dragonflies and damselflies on the wing over open water or along shorelines. At rest they hang from vegetation by their long legs. The larvae, called nymphs or naiads, are predators too. A spring-loaded lower lip, the labium, grabs prey and pulls it into the jaws, and because the rectum also holds the gills, the nymph can launch that attack by forcibly expelling the water it uses to breathe.
Each wing is powered separately, so dragonflies fly forward and backward, up and down and sideways, and hover. That helps them hunt and escape birds, spiders, frogs, fish and lizards.
Migration
Unlike many dragonflies, some green darner populations migrate. They have been seen flying south along the Oregon coast in late September and October, sometimes in swarms of mixed dragonfly species that make a banquet for purple martins, Swainson’s hawks and merlins.
Life cycle
| Stage | What happens |
|---|---|
| Mating | Males fly low and fast over wet areas and shorelines looking for females, and mate in the "mating wheel" position, sometimes flying like that for several minutes |
| Egg laying | The female stays connected in "tandem," which may let the male guard her from other males, while she inserts batches of hundreds of eggs into decaying plant material in the water |
| Larvae | Eggs hatch after about a week; the larvae molt up to a dozen times |
| Emergence | The last larval stage climbs out, breathes air, attaches to vegetation and begins metamorphosis; a winged adult emerges from a crack in its old skin and pumps fluid into its body and wings to stiffen them |
| Adult | The newly emerged "teneral" is highly vulnerable until its body is stiff and colored; adults live a few weeks to a month, depending on climate and migratory status |
Fun facts
- "Darner" is a folk name, for the insect’s likeness to a darning needle.
- The compound eyes have more than 30,000 simple eyes (ommatidia), see almost 360 degrees around and can see ultraviolet light.
- Dragonflies are among the earliest winged insects, with fossils dating back over 300 million years, before the dinosaurs.
The profile says the species may turn up in wet areas of any Klamath Network park, or away from water during migration.
Sources
- National Park Service, Klamath Inventory and Monitoring Network, "Common Green Darner", Featured Creature, October 2022, prepared by Sonya Daw (https://www.nps.gov/articles/000/common-green-darner.htm). The page’s photographs are by outside photographers under Creative Commons licences and are left out; rewritten in hubnx's own words.