Here is the Cicada. This is one from the 17 year cycle. What is interesting about these bugs, is that they appear every 13 or 17 years. There are others in other cycles but the most come out either every 17 or 13 years. Now the science behind that is that 13 and 17 are both prime numbers. Which means that other species have to follow the same life cycles to pose a huge threat to these bugs. Their survival is thus in their numbers and their hard to catch up to life cycles. Nature is indeed wonderful.