The niftily named Carson wandering skipper — a butterfly that is no bigger than a thumbnail — has been given emergency protection under the U.S. Endangered Species Act. The feds took the step yesterday to help preserve the butterfly’s habitat in two counties along the northern border of Nevada and California. Bob Williams of the U.S. Fish and Wildlife Service said officials were concerned that if water export proposals in the region went forward, the insect would go the way of the dodo. The wandering skipper was once plentiful in the region, but development has destroyed most of the butterfly’s habitat.