Anax junius

Large size and bright green coloration distinguish adults from most other North American dragonflies. The combination of green thorax, green abdomen with blue markings (males) or plain green/brown (females), and clear wings with amber bases separates this species from other darners. Similar species include Anax longipes (comet darner), which has red abdomen and blue eyes, and Anax walsinghami (giant darner), which is larger with more robust build and different abdominal patterning. In flight, the green darner's powerful, direct flight with occasional gliding contrasts with the more fluttering flight of smaller dragonflies.

Adults utilize diverse open habitats including wetlands, ponds, lakes, streams, and terrestrial areas far from water during migration. Nymphs develop in still or slow-moving waters: ponds, lakes, marshes, and slow streams, including eutrophic conditions. Tolerant of temporary waters and disturbed habitats. Found from sea level to montane elevations.

North America from southern Canada through United States to Panama; Caribbean islands; Tahiti; Asia from Japan to mainland China. In North America, breeds throughout range with migratory individuals moving north in spring and south in fall. Genetic evidence indicates intercontinental gene flow with minimal population structure across vast distances.

Adults present year-round in southern parts of range; in northern areas, adults appear in spring (March-May) from migratory arrivals, with local emergence June-September. Two cohorts in many populations: summer generation (emerges June-September, 3-month development) and overwintering generation (emerges following June, 11-month development with diapause). Peak flight activity during warm, sunny conditions.

Nymphs are generalist aquatic predators, capturing prey with extensible labium; diet includes aquatic insects, tadpoles, small fish, and other invertebrates. Adults are aerial predators capturing flying insects including mosquitoes, flies, butterflies, moths, and smaller dragonflies. Foraging occurs during continuous flight or from perches.

Hemimetabolous with aquatic nymphal stage and terrestrial adult stage. Eggs laid into water or aquatic vegetation. Nymphal development includes 10-12 instars. Two developmental pathways: rapid summer development (~3 months, no diapause) or extended overwintering development (~11 months, with diapause as half-grown larvae). Emergence typically nocturnal, beginning after sunset. Adults live several weeks to months. Threshold temperature for development: 8.7°C; summer generation requires ~1332 degree-days.

Strong migratory behavior with seasonal mass movements; southbound migrants travel up to 2,800 km. Radio-tracking reveals alternating periods of migratory flight and energy replenishment, with responses to wind and temperature similar to avian migration. Adults regulate thoracic temperature during flight through behavioral adjustments: gliding less, flying faster, and increasing wingbeat frequency as ambient temperature decreases. Endothermic during flight with active thermoregulation. Males patrol territories and defend oviposition sites; tandem oviposition with female dipping abdomen into water while in flight with male attached.

Top predator in both aquatic (nymph) and aerial (adult) ecosystems. Nymphs regulate populations of aquatic invertebrates and small vertebrates. Adults consume significant quantities of flying insects including pest mosquitoes. Serve as prey for birds, fish, frogs, and other predators. Important bioindicator species for wetland ecosystem health.

Popular among dragonfly watchers and photographers due to large size, bright coloration, and approachable behavior. Used in behavioral and physiological research including studies of migration, thermoregulation, and pesticide effects. Nymphs occasionally used as bait by anglers. Subject of citizen science monitoring through Migratory Dragonfly Partnership. Common name derives from resemblance to darning needle.

• Anax longipes (comet darner)Similar size and build but distinguished by red abdomen and blue eyes versus green coloration of A. junius
• Anax walsinghami (giant darner)Larger size (up to 11 cm), more robust build, different abdominal patterning with blue and green rather than uniform green with blue markings
• Anax parthenope (lesser emperor)Old World species similar in appearance but with brown eyes and different wing venation; not sympatric in North America

• dragonfly
• darner
• migration
• predator
• thermoregulation
• citizen science
• wetland
• aerial predator
• endothermy

• BugGuide
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• Bug Spotlight | Entomology Research Museum
• Citizen Scientists Needed for the Migratory Dragonfly Partnership
• Buprestidae | Beetles In The Bush | Page 9
• This Dragonfly's Migratory Route is Even Longer than the Monarch Butterfly's
• ambush bugs | Beetles In The Bush
• dragonflies | Beetles In The Bush
• Migration in Odonata: a case study ofAnax junius
• The foraging behavior of Anax junius (Odonata: Aeschnidae) and its potential as a behavioral endpoint in pesticide testing
• EFFECT OF TEMPERATURE ON THE LIFE-CYCLE OF ANAX JUNIUS (ODONATA: AESHNIDAE) IN CANADA
• INFLUENCE OF TEMPERATURE AND HUMIDITY ON THE EMERGENCE BEHAVIOUR OFANAX JUNIUS(ODONATA: AESHNIDAE)
• The effects of chlorpyrifos on cholinesterase activity and foraging behavior in the dragonfly, Anax junius (Odonata)
• The Diet and Foraging Behavior of the Larval Dragonfly Anax Junius (Aeshnidae), with an Assessment of the Role of Refuges and Prey Activity
• Dependence of Flight Behavior and Heat Production on air Temperature in the Green Darner Dragonfly Anax Junius (Odonata: Aeshnidae)
• AN EXCEPTIONALLY EARLY AND INFORMATIVE ARRIVAL OF ADULTANAX JUNIUSIN ONTARIO (ODONATA: AESHNIDAE)
• Genetic diversity and widespread haplotypes in a migratory dragonfly, the common green darner Anax junius