Given the overwhelming diversity that characterizes the insect world – there are millions of species currently in existence, and they could constitute up to 90 percent of all animal life forms on earth – it may come as a surprise that up until very recently, there were believed to be no amphibious insects. This long-held assumption changed when researches in Hawaii discovered caterpillars that were just as comfortable living on land as they were underwater. The caterpillars, of which there are several species, belong to the genus Hyposmocoma, which encompasses about a third of all butterflies and moths found in Hawaii. (Members of the genus are exclusively found in Hawaii as well.) Below we provide an overview of these amphibious caterpillars, the only known insects in the world, and possibly the only animals in the world, that are adapted to live on land and underwater.