I was thrilled to see Blackline Hawaiian Damselflies — Megalagrion nigrohamatum nigrolineatum — high in the northern Koʻolau Mountains at about 2,000 feet elevation.
With the recent discovery of a previously unknown remnant population of Blackline Hawaiian Damselflies at low elevation in Kāneʻohe, I needed more photos of them at high elevation. So I hiked high into the northern Koʻolau Mountains to look for and photograph them. Blackline Hawaiian Damselflies are endemic only to O’ahu. They were once widespread at all elevations but since the 1970’s their numbers have crashed due to habitat loss and predation/competition from introduced species.
In 2012 Blackline Hawaiian Damselflies were put on the federal list of endangered species. Only an estimated 1,000 of these damselflies remain in 16 known populations. With the exception of the recently discovered population in Kāneʻohe that somehow found a way to survive at low elevation, the only damselflies left are high in the Ko’olau Mountains.
I was captivated to see how the high elevation damselflies came in an array of different colors. There is lots of variation in the color of their thoraxes and eyes. The Hawaiian name is pinapinao ānuenue — rainbow eye damselfly — an appropriate name for such a colorful insect.
By watching them mate and lay eggs I observed multiple color morphs. Males take the front position and grasp the female with a grabber at the end of his abdomen just behind the female’s head. Females curl their abdomen forward to a spot under the males thorax where she fertilize her eggs with his sperm.
They then fly to freshwater where the female inserts her ovipositor into the water so she can lay her eggs on the vegetation underwater.
The eggs hatch into nymphs where they live underwater. After several molts the aquatic nymphs move on to the next stage in their life cycle and transform into flying adults.
The male is able to stand erect without beating its wings held in place by the grabber at the red tip of his abdomen.
This purple colored damselfly is the rarest color morph I observed. I have only seen this one individual. Pinapinao ānuenue – literally “rainbow damselfly” – is a fitting description for a creature that comes in multiple hues.
The discovery of a previously unknown population of low elevation Blackline Hawaiian Damselflies in Kāneʻohe is a remarkable and significant find. Rainbow damselflies are unique to the natural history and heritage of O’ahu and need to be protected.