Overview
The Pacific Spiketail (Cordulegaster dorsalis) is a colossal, powerful mountain dragonfly that patrols the clear, rushing mountain torrents and cascading creeks of the western cordillera. Wielding immense, glowing turquoise-green compound eyes and a long, dagger-like spike at the tip of the female’s abdomen, this formidable aerial hunter flies like a miniature attack helicopter along shaded forest stream corridors.
Biology and Physical Characteristics
Cordulegaster dorsalis has a long, heavy, cylindrical abdomen colored deep velvety brown-black, patterned with prominent bright lemon-yellow triangular spots and arrowheads along the dorsal spine. Its massive compound eyes meet at a single point on top of the head and glow intense emerald-green to cyan in life. Females feature an exceptionally long, spike-shaped ovipositor that extends far beyond the abdomen tip.
Behavior and Ecology
A master of low-altitude stream patrol, the Pacific Spiketail flies rhythmic beats up and down rushing mountain creeks just inches above the water, seizing flying caddisflies, stoneflies, and wasps in mid-air with spiny basket-like legs. To lay eggs, the female hovers vertically over shallow gravel beds, repeatedly thrusting her abdominal spike into sandy gravel like a miniature sewing machine needle.
Conservation and Human Impact
Assessed as Least Concern by the IUCN, the Pacific Spiketail maintains healthy populations in pristine mountain watersheds across the Cascades and Sierra Nevada. Because its predatory aquatic nymphs require clean, silt-free gravel beds and cold, well-oxygenated water over several years, it is highly sensitive to stream siltation from logging and road construction.
Interesting Factoid
Female Pacific Spiketails lay eggs like a flying sewing machine: they hover upright over mountain streams and rhythmically hammer their long spike-like ovipositor down into the river sand hundreds of times to bury their eggs safely away from predatory trout.