Euphorbia celastroides var. stokesii
Galling on native ʻakoko. Deforms new (terminal) growth and causes these "galls."
Kīlauea Lighthouse, Kīlauea Point National Wildlife Refuge, Kauaʻi
Thanks to Scot Nelson for his tentative identification as "probably psyllid* injury."
*Psyllids or 'jumping plant lice' are small phytophagous, phloem feeding insects that are typically monophagous (feed on a single plant) or oligophagous (feed on a few related plants). Together with aphids, coccids and whiteflies they form the monophyletic group, Sternorrhyncha (Homoptera), which is considered basal within the true bugs (Hemiptera).