Patterns of extinction across Hawaiian Lepidoptera offer lessons from a diverse, neglected, and vulnerable endemic fauna

Although insects make up the overwhelming majority of the described life on Earth, virtually nothing is known about the conservation status for all but the most charismatic taxa (i.e., butterflies, dragonflies) and many are at risk of imminent extinction. Given that island faunas are particularly vulnerable to extinction, we examined the conservation status of all 935 described species of native Lepidoptera in Hawaiʻi as a model to better understand levels of threat in poorly-known groups and how their rates of extinction might warrant actions to conserve them and inform future management. Using 100- and 50-year cut-offs for the time since each species was last recorded, we consider 269 species (28.8%) to be “presumed extinct,” 85 species (9.1%) to be “possibly extinct,” and 581 species (62.1%) to be “extant” or “likely extant,” giving an extinction rate with an upper bound of 37.9%. Baseline data such as these are crucial in establishing which taxa persist and which lineages may be most vulnerable to extinction in the immediate future. Continued field surveys and identification of museum specimens are critical to more precisely quantify extinction rates, focusing on taxa requiring the most immediate conservation action, and may result in the rediscovery of some “presumed extinct” species. We discuss discrepancies in extinction rates across taxa and between islands as well as summarizing major threats and obstacles to protecting the Hawaiian Lepidoptera fauna going forward. Conservation specifically geared towards Hawaiian Lepidoptera is almost non-existent, which is inconsistent with the extreme rarity and high rates of extinction across many lineages.