Damselflies, dragonflies show amazing adaptations
Twenty-million years ago the Hawaiian Island chain was only a few links long. Midway Atoll and Gardner Pinnacles were the prominent islands in the archipelago and the main Hawaiian Islands were merely raw lava flowing through the interior of the planet. Around this time a damselfly arrived to the chain, beating the odds in a successful journey across half an ocean.
This single event led to the evolution of some 26 species and subspecies of native damselflies in Hawaii that exist today, according Dan Polhemus, Ph.D., the aquatic ecosystem conservation program manager for the Pacific Islands Fish & Wildlife Office within the U.S. Fish and Wildlife Service. He has studied dragonflies and damselflies throughout the Pacific as well as here on Maui.
Perhaps our most spectacular native insects, damselflies and dragonflies were once widespread throughout the islands. Known as pinao in Hawaiian, these insects now exist only in a tiny portion of their historic range. Introduced predators and habitat loss are to blame. Several species are so rare that they are listed as threatened or endangered. They are often extremely localized; some species are only found in a single stream.
Pinao adapted to take advantage of the resources available in Hawaiian ecosystems. They live in a remarkable range of habitats, from mountain streams to marshlands and brackish anchialine pools.
Perhaps because stream flow is often intermittent, some species adapted to survive outside of streams and pools. There are naiads (larval stage of development) that take advantage of water seeps and pockets of rain that collect in the leaves of ieie vines. One species of damselfly is completely terrestrial — an adaptation existing in only a few other damselfly species in the world. Their young live in the moist understory of uluhe fern and lack gills found during other damselfly species’ naiad stages.
These hunters evolved eating small insects, both in the water and as they fly through the air. Today, pinao eat a variety of prey, including introduced insects. “They are essentially midair fighter planes,” says Polhemus. They hunt by folding their legs into a basket to snatch insects from the air. But these aerial predators are prey nowadays.
Lowland marsh and riparian areas have been converted and streams have been diverted. “Intermittent pools have a lot of invasive species,” says Polhemus. Without regular flow to flush out the introduced aquatic species, these pests, such as mosquito fish, become established. While the handful of introduced dragonflies have fish-avoidance behaviors, the native species, having spent the last 20 million years without predators, are easy prey for non-native fish and other insectivorous invaders. Like native birds in the face of tree-dwelling predators like rats, the larvae are easy picking for voracious mosquito fish. “Where mosquito fish are present, you don’t find native damselflies'” says Polhemus.
Bullfrogs and bulbuls (an invasive bird not present on Maui but found elsewhere in Hawaii) also pose a threat to these ancient colonizers. Bullfrog tadpoles eat dragonfly naiads and bulbuls have been seen snatching the insects from the air.
Ants are another predator. The young naiads climb out of the water to morph into adults on land. Their skin splits open and wings unfold. As they wait for their skeleton to harden and wings to dry, they are vulnerable to invasive ants.
There are several species of introduced dragonflies, and most of the dragonflies at low elevation are introduced species able to survive amongst other introduced aquatic pests. The native dragonflies and damselflies (distinguished from dragonflies by their ability to fold their wings back at rest) are now found mostly in upper elevations in the Hawaiian Islands, with two species found only on Maui. The largest dragonfly in the United States is found only in Hawaii. Anax strenuus, the Hawaiian giant dragonfly has a wingspan of 6 inches.
You can help protect these unique animals: If you can no longer care for your fish or other aquatic friends, give them to someone who can. Never release them into the wild as they can cause ecological damage by pushing out native species, which play an integral role in a healthy Hawaiian ecosystem. Support legislation to maintain stream flow and prevent pollution. To learn more about these fascinating creatures visit: https://dlnr.hawaii.gov/wildlife/files/2013/09/Fact-Sheet-Odonata-damselflies-dragonflies.pdf
* Lissa Strohecker is the public relations and education specialist for the Maui Invasive Species Committee. She holds a biological sciences degree from Montana State University. “Kia’i Moku,” “Guarding the Island,” is prepared by the Maui Invasive Species Committee to provide information on protecting the island from invasive plants and animals that can threaten the island’s environment, economy and quality of life.