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The Mariana eight-spot butterfly (Hypolimnas octocula marianensis) and the Mariana wandering butterfly (Vagrans egistina) are endemic to the Mariana Islands and both have recently been listed as federally protected under the U.S. Endangered Species Act. We conducted both targeted surveys and grid transect searches on Guam and targeted surveys across the islands of Saipan, Tinian and Rota to locate native hostplants, eggs, caterpillars and adults of these rare insects. Despite having a relatively common hostplant, V. egistina was not found during this study, even in places it had last been found. Although various life stages of H. o. marianensis were documented, the hostplants of this species were heavily impacted by grazing of introduced ungulates; only in native limestone forest with jagged tower karst topography, did hostplants persist, and the butterfly with them. The reasons for the disappearance of V. egistina are not clear, but do not appear to be related to hostplant availability. Our surveys suggest that control of invasive ungulates on Guam will be the single most effective conservation action for Mariana eight-spot recovery, and is essential to any chance of long-term persistence for the species there. H. o. marianensis has significant, unoccupied, hostplant patches on the three northern islands (Rota, Tinian, and Saipan) which might be considered as sites for future translocation and reintroduction efforts, in order to reduce the risk of extinction.

The Holarctic Saturniid genus Saturnia contains eight subgenera, though their taxonomic ranks have been in flux for decades. A prior biogeographic analysis with a six gene molecular phylogeny of Saturnia including 34 species and representatives of all but one subgenus supports distinct divisions that require taxonomic changes to accurately reflect their biology and phylogeography. In the current study, we add more publicly available COI sequence data to the previous dataset, and include all subgenera, which resulted in a dataset with approximately 67 species. Based on inferred phylogenies of the 34-species and 67-species datasets as well as the biogeographic analyses, we propose to elevate six subgenera to genus level: Agapema Neumoegen & Dyar 1894 stat. rev., CachosaturniaNaumann, Loffler & Nassig 2012stat. nov., Calosaturnia Smith 1886 stat. rev., Neoris Moore 1862 stat. rev., Perisomena Walker 1855 stat. rev., Rinaca Walker 1855 stat. rev. Additionally, we synonymize Eudia Jordan 1911 syn. nov. with Saturnia Schrank 1802 because it renders Saturnia paraphyletic, and confirm the previous synonymization of Eriogyna Jordan 1911 with Saturnia and of Caligula Moore 1862 with Rinaca Walker 1855. With these changes, molecular phylogeny and biogeographic analysis has informed taxonomy of a prominent, but poorly-understood group and revealed how the complex biogeography and active biotic exchange across the northern hemisphere has promoted diversification in previously unrecognized groups.