Single specimen informs the evolutionary history and endangerment status of the high-elevation Haleakala beetle, Blackburnia lenta (Coleoptera: Carabidae)

The Hawaiian carabid beetle Blackburnia lenta is restricted to high-elevation scrubland habitats west of Koolau Gap along the northwest rift of Haleakala volcano, Maui. This species, described from four specimens collected in 1894, was next seen in nature in 1975. Critically endangered status for B. lenta is supported by the occurrence of Argentine ant—Linepitheme humile (Mayr)—near or adjacent to the species’ extremely limited geographical distribution. A single male Blackburnia specimen collected on Kalapawili Ridge, across Koolau Gap from the known range of B. lenta, represents the undescribed adelphotaxon to B. lenta. This discovery: 1, reaffirms that the geographic range of B. lenta is limited to the previously known scrubland habitats west of Koolau Gap, all within close proximity to colonies of invasive Argentine ant; 2, maintains critically endangered status for this species without the option of a predator-free zone as part of its distributional range; and 3, dates the time of vicariance between B. lenta and its adelphotaxon as the age of volcanic flows that filled Haleakala Crater and Koolau Gap 120,000-150,000 years ago.