It was reported in December 2005 that the Hawaiian "wiliwili" population was under immediate threat due to an infestation by a gall wasp, "Quadrastichus erythrinae", which had been first reported in Hawaii in April of that year. This invasive species appears to have arrived in Hawaii via southern Taiwan, Singapore and southern China within only two years. This species was not previously known to science and was formally named and described in 2004. It is thought to have originated in Africa, and the means of its rapid dispersal across South Asia, the Pacific, and southern North America is not understood. The majority of trees of introduced "Erythrina" species have died as a result of gall wasp infestation. Native "wiliwili" forests have also been hard hit, particularly Puu o Kali on the island of Maui - prior to 2001, the best remaining example of a Hawai'i low elevation dryland forest ecosystem. The USGS-Pacific Island Ecosystems Research Center study site now documents the destructive impact of two invasive insect species (African bruchid beetle "Specularius impressithorax" and erythrina gall wasp) on Erythrina sandwicensis.