Their sound is so much a part of an August evening. A gradual hum that breaks out into a roar. They break through the ground and head in groups for the nearest tree. The nymphs remain underground for 17 years feeding on tree roots. Their number is so great that they provide an unending meal for turtles, racoons and birds. Every year a new group emerges in some area of the US, which is the only country where they are found. Only the males are capable of their unique sound which is used to attract females. Eric Day, an entomologist, recommends frying them in sake and garlic because of their high protein content. They are not poisonous and will do no harm to humans. They are a bit clumsy and will slam into you when you least expect it. Cicadas are extremely vulnerable to predators while they are waiting for their wings to dry after they emerge, but in spite of this, billions manage to survive, mate and die off leaving their nymph eggs to settle underground for another 17 years.