Hungry, Hungry Hawaiian Caterpillar: Program Aims to Restore the Endemic Kamehameha Butterfly
By Adrienne Antonsen
The Kamehameha butterfly (Vanessa tameamea) is one of two butterfly species endemic to Hawai’i. It used to be widespread across the island archipelago. As humans transformed the environment, however, the native nettle species used by the butterfly as hosts became less common, and nonnative predators such as ants, wasps, and birds spread across the landscape. The butterfly and the nettles are now largely restricted to high-elevation forests where the steep terrain limits development. The Hawai’i Invertebrate Program (HIP) is on a mission to bring the butterfly and its host plants back to their former glory.
Funded by Hawai’i’s Department of Land and Natural Resources, Division of Forestry and Wildlife, the HIP captive-rearing program was established in 2016 with the goal to protect and restore native invertebrates. For the Kamehameha butterfly, known as pulelehua in Hawaiian, this involves reestablishing habitat with native nettles and then releasing captive-bred individuals into those areas to start new breeding populations.
Of Hawai’i’s native nettles, the pulelehua are particularly keen on the māmaki plant (Pipturus albidus). In addition to being a host plant for the Kamehamea butterfly, māmaki can be brewed to make an antioxidant-rich tea. HIP grows māmaki plants on site for restoration transplants and to feed the lab-reared caterpillars.
Raising the Kamehameha butterflies is a labor of love. During each two-generation rearing cycle, the HIP team tracks the pedigree of every butterfly to minimize inbreeding. Adults lay eggs in an onsite enclosure, and when the first instar caterpillars hatch each one is placed in its own cup with a bit of māmaki to munch on. Lab members check each cup every other day to assess the caterpillar’s status, remove frass, and replace the previous day’s māmaki with freshly harvested leaves. Once the caterpillar forms its chrysalis, lab members cease feeding and await metamorphosis. Development from egg to adult takes about 40-45 days.
Since 2017 the Hawai’i Invertebrate Program has gone through four rounds of Kamehameha butterfly releases, each round raising two generations over four to five months. Release sites lie within the species’ historical range, have native nettles restored, and don’t overlap with any extant populations. The team released pulelehua both as adults and as eggs. Despite caterpillars being detected after each release, second generations have not successfully established. It appears that predation upon the caterpillars is simply too high.
Despite the hurdles the Kamehameha butterfly faces, from habitat loss to invasive ants and moths, HIP has already made great strides in protecting the iconic species. In less than four years the HIP team has determined the species’ current distribution, helped establish host plants into reintroduction sites, and learned how to breed the butterflies in captivity. The team is now planning to track deployed caterpillars with 24/7 cameras to determine exactly what is preying upon them at the release sites. Once that is determined, they intend to develop strategies to curb predation and help the caterpillars persist long enough to establish breeding populations.
In addition to the Kamehameha butterfly, the Hawai’i Invertebrate Program has ongoing conservation projects for the orangeblack Hawaiian damselfly, yellow-faced bees, Kauai flightless stag beetles, and more.
Hawai’i Department of Land and Natural Resources
Adrienne Antonsen is a graduate student in entomology at North Dakota State University. Email: firstname.lastname@example.org