Cicadas!!By Vivienne and Sarina

All about Periodic Cicada’s!The Periodic Cicada is an Insect that lives underground for total 17 years of its life. Through these 17 years, the cicada feeds on the root sap of trees. After living underground for so many years they all crawl up out of the ground by digging through the soil and onto the trees. After a long journey crawling up the tree, the cicada sheds it’s skin. Then for a day the Males make a clicking sound to show that they want a mate. Once they find one their babies crawl into the ground again to wait another seventeen years. They live in Australia, Japan, South America, and North America. They come out every 17 years because there are less predators that won’t come out for more than 100 years.

Cycle Length(years)

Predator A(2)

Predator B(3)

Predator C(4)

Next attacked by all three predators

10 2010 2030 2020 2060

11 2022 2033 2044 More than 100 years

12 2012 2012 2012 2012

13 2026 2039 2052 More than 100 years

14 2028 2042 2056 2084

15 2030 2045 2060 2060

16 2032 2048 2064 2096

17 2034 2051 2068 More than 100 years

18 2036 2054 2072 2072

The Cicada Graph

Our Working Out

Questions…Which cycle lengths are more than 100 years before the cicadas are attacked by all 3 predators? What did you notice about these numbers? 11, 13, 17. They are all the only prime numbers of the chart.

Explain why you think this happens. This is because since the prime years are more than 100 years, the cicadas have a much higher chance of survival. It is always the prime numbers because since they are only divisible by themselves, it is very rare to have a prime year be divisible by 2, 3, and 4 all together.