Yellow-winged Darter Sympetrum flaveolum

This dragonfly breeds in peat bogs across Europe and northern China, but here's where it gets weird: it occasionally invades the United Kingdom in massive numbers—documented in 1906, 1926, 1945, 1953, and 1995. Each invasion spawns temporary breeding colonies, but they mysteriously fail after a few years. It's like a periodic dragonfly gold rush that never quite manages to establish itself.