A Characterisation of the Invasive Lema Beetle, Lema equestris (Coleoptera: Chrysomelidae), in Hawaii

Abstract

Introduced to Hawaii in 2019, Lema equestris has become a garden pest commonly reported on Solanum americanum, which is grown as a native and cultural plant in Hawaii and supports native vertebrates elsewhere across Oceania. Originally identified as L. solani, the species was later found to have been misidentified. Here, molecular and morphological evidence is used to discriminate Hawaiian specimens from L. solani and support the updated identification of L. equestris. As a new invasive species, it is important to confirm host associations and determine whether it will prey on important species, such as endemic or endangered plants, in its new range or any potential range to which it could spread. To this end, feeding assays were performed with adults, first-instar larvae, and newly hatched naive larvae on 11 potential hosts, comprising mostly Solanum species: Solanum americanum, potato, tomato, tomatillo, poha (gooseberry), chili pepper, eggplant, tobacco, tree tobacco, cabbage, and Brazilian nightshade. While feeding was attempted on cabbage, poha berry, and Brazilian nightshade, no host besides S. americanum supported survival. Rearing was used to further characterize the biology and life history of L. equestris, including instar length and distinctive morphological traits for identifying each life stage. While many basic biological traits are confirmed here, much remains to be studied to better understand this species and why it has begun to spread.