The sum of the absolute frequencies is equal to the total number of data, represented bas $$N$$. 1  Relative frequency: the result of dividing the absolute frequency of a certain value by the total number of data.  The sum of the relative frequencies is equal to $$1$$. We can prove this easily by factorizing $$N$$.
Periodical cicadas emerge from underground every 13 or 17 years, depending upon which brood the cicadas belong to. The year a particular brood emerges often differs from other broods and is also dependent on geography. The periodical cicada, although unrelated, is often mistakenly called a locust.
âItâs a garish beast.â. In its ecosystem role, the cicada invasion is like a Las Vegas smorgasbord for animal and bird predators. âEverybody eats 17-year cicadas. One evolutionary advantage of being underground for 16 years is that no above-ground predator can specialize in eating the periodical cicadas,â says Gilbert.For cicadas, the best defense simply may be predator satiation.âThere are so many cicadas, that predators get full, and they canât eat another bite.ne evolutionary advantage of being underground for 16 years is that no above-ground predator can specialize in eating the periodical cicadas,â says Gilbert. For cicadas, the best defense simply may be predator satiation. âThere are so many cicadas, that predators get full, and they canât eat another bite.