This Butterfly May Have Been the First Insect Driven Extinct by U.S. Urbanization The beautiful Xerces blue butterfly was a distinct species, according to a new study. It hasn't been seen alive since 1943. By Photo: Field Museum Scientists say they’ve confirmed a decades-old suspicion about the loss of the Xerces blue butterfly in the U.S by the 1940s. Based on genetic analysis of a 93-year-old specimen and others, they say the Xerces blue really was a distinct species of butterfly, rather than a sub-group of another existing species, as some scientists have speculated. If true, it would reaffirm the end of the butterfly as the first known insect extinction in the U.S. tied to urbanization.