We present the first molecular phylogeny of the endemic Hawaiian radiation of Nysius seed bugs, including the unique and anomalous wekiu bug, Nysius wekiuicola Ashlock and Gagné. The Hawaiian Nysius contain about a quarter of the world’s species in the genus, with the wekiu bug (and its sister species the Mauna Loa bug, N. aa) showing the most extreme deviation from the standard Nysius character set. The Hawaiian Nysius seed bugs are widely distributed in drier environments on all of the Hawaiian Islands. While all other Nysius are seed-feeders, N. wekiuicola and N. aa are both flightless, micropterous, cold tolerant, scavenger-predators of moribund insects on the 13,790 ft volcanoes of Mauna Kea and Mauna Loa on the island of Hawaii. The wekiu bug is a candidate for listing under the Endangered Species Act, due to its decreasing numbers, limited range, specialized habitat requirements, isolated populations, and habitat destruction. Low levels of mtDNA variation suggest that the wekiu bug and Mauna Loa bug are very recently diverged. In addition, they are closely related to other Hawaiian Nysius possibly indicating a rapid adaptive shift from the standard morphology and host feeding of the rest of the Hawaiian seed bugs. These results are presented in the broader context of a Hawaiian Nysius molecular phylogeny.