Aquatic invasions

environments: they believe these are the only insects able to do so. As a further adaptation to living around flowing water, they withstand extremely high and fast floodwaters. “Through a combination of specialised shelter-seeking and use of silk tie-downs and drag lines, larvae avoid exposure to the strongest currents and quickly return themselves to the substrate if dislodged,” the researchers write. The moth larvae may remain submerged for weeks or live on dry rocks metres from any water, growing on dried algae and lichens, the researchers observed. When submerged, they likely rely on direct diffusion of oxygen through skin on their abdomens, which perhaps explains why they only occur in oxygenated, fast-flowing streams, and quickly die in stagnant water, they suggest. “Across the Hawaiian archipelago we found three previously unknown lineages of moths in the endemic genus Hyposmocoma, each with multiple species whose caterpillars can develop both under water in streams and on dry land with no access to water”, the researchers write. “This previously unrecorded phenomenon makes these species truly amphibious in a way unmatched by any other insect,” they say. The unusual array of species on the islands may have helped. “Hawaiian streams lack nearly all of the insect orders or families that dominate continental aquatic ecosystems, and this ecological opportunity may have had a prominent role in the evolution of Hyposmocoma’s amphibious larvae.”