Columbia clubtail (dragonfly) (Gomphurus lynnae)

Physical description

The Columbia Clubtail is a medium-sized dragonfly in the family Gomphidae.   It is about 54 mm to 60 mm long.  Both males and females are black and yellow patterned, with blue eyes and a yellow face.  There is a powdery substance (known as pruinosity) on the thorax.  Both sexes display a distinctive club at the end of their abdomens; the male’s is a little larger.  This species was discovered in Washington in 1971 and described in 1983. It is the most recently described dragonfly in the Pacific Northwest.   

Ecology and life history

Over its range, Columbia clubtail use slower-moving, open sandy to muddy rivers with gravelly rapids in sagebrush-riparian woodland.

Clubtail dragonflies complete a life cycle composed of two main phases: a flightless aquatic larva (nymph stage), which may be continuous for one to two winters, and the adult flight (reproductive stage). They inhabit sites year-round as egg, larval nymph, and adult, typically moving within only a few to several hundred meters of their natal locations. Adults do not seasonally migrate and die soon after their reproductive summer.

Both life stages are predatory; the majority of life cycle is spent as aquatic larvae. Nymphs feed on aquatic invertebrates and possibly small vertebrates (fish, frog and salamander larva). After multiple aquatic instars (gradual metamorphosis) over one or two winters, mature nymphs crawl onto rocks or vegetation and shed their exoskeleton to become a new adult (teneral) in late spring and summer.

Adults are aerial predators of smaller insects and similar sized butterflies and moths (Lepidoptera), as well as smaller Odonates.

Water temperature influences the timing of emergence from within a year or over two years. Weather influences flight period duration, with wet or cold conditions potentially shortening the flight period and warm, dry conditions promoting the duration and later occurrence dates of the flight period.

Male clubtails seek mates by patrolling a territory that coincides with optimal aquatic habitat for female egg-laying, and hence for larvae. There is usually no courtship behavior. After copulation, females usually hover just above the water of slow moving or gentle current stretches and close to shore while periodically dipping the tail to deposit multiple eggs.

Geographic range

The Columbia Clubtail has been found in north central Oregon to the southeast in Gilliam, Malheur, Sherman, and Wheeler Counties on the John Day, Owyhee, and Malheur Rivers in Oregon.  In Washington, it is known from stretches of the Yakima River and from Lower Crab Creek in Grant County.  In 2020, a record was documented from the Walla Walla River.