Atlas Obscura has an interesting story about how white-letter hairstreak eggs have been found in Scotland for the first time since 1884. They used to be fairly common but the population declined for a number of reasons. One of them was Dutch Elm disease, since elm trees were favored plants for the caterpillars to feed on. Now the butterflies appear to be moving north from southern regions again. Some scientists link it to a warming climate but no studies have been undertaken to look at this.
