Which insects "stop" trains in Japan every eight years?

Every eight years during fall, a plague of millipedes swarm train lines in mountainous Japan, earning them the nickname 'train millipedes'.

Working together, these small beasties (around 3 cm or 1.18 inches long) - which play a large role cycling nitrogen in Japan's larch forests - have forced trains to come to a skidding halt.

Up until now, scientists weren't quite sure what was causing them to swarm with such peculiar regularity, but a 50-year research project has finally confirmed that the species - Parafontaria laminata armigera (P. l. a.) - exists on a rare eight-year life cycle.

This confirmation is incredibly exciting, as cicadas are the only other known periodical animals with lifespans this long.