Hawaii Invasive Species Council

Ramie Moth (Arcte coerula)

What You Can Do: Report this species to 643pest.org or call 808-643-7378 (643-PEST) if seen anywhere in Hawaiʻi. If you do see ramie moth, location, number of eggs/caterpillars found, and the number of host plants around/surveyed are very helpful details to include. Please take a few photos if possible. Caterpillars and eggs can be collected alive and brought to UH Mānoa. Please email [email protected] for details on where to drop off live specimens and who to contact if found.

• “Ramie moth has been detected on Maui and Hawaiʻi Island. Larvae have been recorded in both residential areas and native forests. Further surveying will be conducted by the University of Hawaiʻi to identify additional locations where this pest may be found.” (CTAHR)
• Most recently, it was found on Oʻahu in 2024 in the Ewa Forest Reserve (Poamoho section).
• Update: Ramie moth has now also been detected on Kauaʻi (2025) and Lānaʻi (2026). Please report sightings of this species on any island.

Photo credit above: HDOA

Photo credit above from top to bottom: Michelle Au, HDOA, DLNR

Kamehameha butterfly vs. ramie moth:

• The pulelehua or Kamehameha butterfly (Vanessa tameamea) is Hawaiʻi’s state insect. It can resemble ramie moth caterpillars, so careful identification is important to avoid harming endangered native species.
• “Although the butterfly is historically known from all the main Hawaiian Islands (Kauaʻi, Oʻahu, Molokaʻi, Lānaʻi, Maui, and Hawaiʻi), it is no longer found in some areas where it used to be common (e.g. Tantalus on Oʻahu), and it appears to be declining.” (CTAHR)

DESCRIPTION:

• The eggs of the ramie moth are clear/white, circular (~1 mm diameter), and laid on the underside of leaves.
• Younger larvae are green and black caterpillars. As they develop, they become bright yellow and black with orange-red spots and thin white hairs.
• Adults are large brown and black moths (65–90 mm wingspan).
• They are often found on or near plants in the nettle family (Urticaceae), including māmaki.
• “Ramie moths are very distinct from other caterpillar species that feed on māmaki because of the aggressive defensive behavior the larvae exhibit. Early instar larvae were observed defensively dropping from leaves when disturbed and moving quickly between leaves on the plant. As later instars, the larva will rear up its head, thrash around, and regurgitate a green liquid to defend itself.” (CTAHR)
• Distribution update: In Hawaiʻi, ramie moth has been detected on Maui (2018), Hawaiʻi Island (2020), Oʻahu (2024–2025), Kauaʻi (2025), and Lānaʻi (2026).
• Please report sightings of this species if seen on any island.

IMPACTS:

• Ramie moth caterpillars feed on young and mature leaves of host plants, causing defoliation and impacting plant health.
• They threaten māmaki (Pipturus spp.), a culturally and ecologically important native plant that stabilizes streambanks and supports numerous native insects, including the Kamehameha butterfly.
• They also feed on maʻoloa (Neraudia melastomifolia), an endangered plant found only in Hawaiʻi.

ERADICATION & CONTROL METHODS:

CTAHR recommendations:

• Currently, the best management strategy is continual monitoring of plants and removal of eggs and larvae when found.
• Eggs are often clustered around a few plants—search nearby plants if eggs have been detected.
• If heavy feeding damage is observed on māmaki leaves, check the area for caterpillars. Early instar larvae can move quickly throughout the plant and may drop to the ground and spread to neighboring areas.
• Monitoring should be done year-round, but caterpillars are often most abundant from December through May.
• In Australia, botanical insecticides (such as neem, derris powder, pyrethrum), insecticidal soaps, and microbial products such as spinosad and Bacillus thuringiensis kurstaki have been used.
• However, these products are not labeled for use in Hawaiʻi on māmaki and are not recommended, as they may impact endemic Lepidoptera that feed on māmaki and other endemic Urticaceae.
• Biological control is currently being explored as a management strategy.

WHAT YOU CAN DO:

• Report this species to 643pest.org or call 808-643-7378 (643-PEST) 
• Use the monitoring and removal techniques above if you have māmaki on your property.
• Learn to recognize differences between caterpillars of ramie moth, Kamehameha butterfly, Udea stellata (native), and green garden looper (invasive) to avoid harming native species. (See the differences here)
• Do not move host plants such as māmaki or ʻolonā between islands or areas without inspection. Plants should be inspected by the Hawaiʻi Department of Agriculture (HDOA) Plant Quarantine Branch prior to transport.