The periodical cicada is native to the eastern United States. It has one of the longest life spans of any insect in the world, but only a fraction of its life is spent above ground. Depending on the species, the insect's life cycle may be either thirteen or seventeen years long. Most of this time is spent underground, feeding on the fluid inside certain types of tree roots. After thirteen or seventeen years, the mature cicadas finally emerge from their underground existence. They are only active above ground for a period of approximately four to six weeks. During this time, groups of male cicadas gather in various locations and "sing" in order to attract females. This loud, metallic buzzing noise is one of the most unmistakable signs of summer in many places. A few weeks after mating, the female cicadas lay their eggs. Within two months, after only a short time spent out in the open air, the adults' life cycle is complete.