Snails, native or alien. I don't have any info that would allow me to positively identify most of the snails I see in the wilderness, though I expect that most of them are natives except for garlic snails. Native snails were once an important part of the Hawaiian ecosystem, but they've suffered greatly by rats, deforestation, and the removal of undergrowth layers within forests which distrupts their lifecycle. The loss of native snail populations is believed to have played a large part in the extinction of some native bird species. I read that the foggy forests around Waimea once supported the highest concentration of land and tree snails on Earth, before much of it was transformed into a barren wasteland of cattle pastures. Many native snails graze on the fungus growing on leaf surfaces, cleaning the leaves!