On the Indonesian island of Sumba, Indonesia, the Pasola War Festival marks the start of the new planting season, and only begins on the arrival of multi-coloured sea worms, which only appear once a year for a couple of days. The quantity and colour of the worms is supposed to indicate the quality of the coming years harvest. It is an ancient fertility ritual in theory, but in practice it is a violent blood sport. Tribes from different villages, mount their ponies and carry long, sharpened wooden spears, the neighbouring tribes square off in mock war.