So the calls and emails have all been coming in. Some people happy and fascinated, others much more fearful, as they think that a great plague is about to strike. The emergence of dozens of cicadas has many people wondering what’s going on. Some are aware of Periodical Cicadas, sometimes called locust in a reference to biblical invasions of insects, others are not.
Indeed, we are in the midst of an emergence of Periodical Cicadas, but not the natural phenomenon of a great cicada year. The Big One is not due until 2021. Cicadas are insects known for the loud songs of the males. While we have numerous species of annual cicadas that come out every year during summer (many of which take more than one year to mature, but they’re staggered in breeding so some are out every year), Periodical Cicada are much different.
Periodical Cicadas (Magicicada species) emerge in huge numbers in late spring, generally on 13 and 17 year cycles. There are 7 Magicicada species, of which 3 are local to the DC area. They generally time themselves so they come out in gigantic numbers, thus the reference to biblical plagues of locust and their alternate name. By all coming out (and earlier in the season before predators like Cicada Killer wasps are active) at one time in such huge numbers, they make it impossible for all of them to be eaten. Though a favorite food, they just are too many to all get eaten. Since they come out after such an extended period of years underground, no single predator has adapted to feed on them exclusively. They just overwhelm all the potential hazards, so though thousands die, millions make it.
Since their emergence is synchronized over different regions, people have divided these regional cycles into Broods. There were 23 different Broods recognized at one time, but some have gone extinct. The DC area is part of Brood X.