Blackburnia gastrellariformis sp. n., is described from East Molokai, Hawaii. Based on cladistic parsimony analysis of adult characters, the species is hypothesized to be most closely related to B. komohana Liebherr & Zimmerman of West Maui, with these two species comprising the adelphotaxon to the East Maui species pair, B. haleakala Liebherr & Zimmerman + B. putealis (Blackburn). Previous reconciled tree analysis for the Hawaiian Blackburnia radiation conducted before discovery of B. gastrellariformis found a general pattern in which Molokai and West Maui were hypothesized as sister-areas to the exclusion of the East Maui volcano, Haleakala, though the less common, incongruent area relationship of (Molokai (West Maui + East Maui) was also represented in the taxon-area cladogram. In the present reconciled tree analysis, the closest hypothesized relationship of B. gastrellariformis and a West Maui species corroborates the more common pattern by replacing items of error in the previous analysis with the newly discovered species. Elevational habitat shifts are invoked to explain the occurrence of numerous sister-species pairs in Molokai and West Maui, currently separated by the Pailolo Channel, relative to species occupying Haleakala.