The cicadas that make up Brood VIII have emerged from hiding, and you’ve probably heard the insect orchestra so hard at work. They want to mate! The sound made by male cicadas — peaceful to some, grating to others — is a product of a complex mating ritual, and it can attract females from as far as a mile away. Thankfully, cicadas are not dangerous: they do not bite or carry disease, and although they can damage trees and tree roots, the damage is minimal and temporary.
Although cicadas appear at regular intervals, there are a few rare outliers that will emerge from their burrows a little bit earlier or later than scheduled. This is probably the result of genetic mutations, but there’s an evolutionary purpose behind them: in the event of a natural disaster that destroys or prevents a brood from emerging from the ground, the brood will still have a good chance to live on through those outliers who emerge early or late.
What kind of natural disaster can spell doom for an otherwise strong cicada brood?
- The Ohio River flooded in 1937 after three weeks of heavy rain and snowmelt left the river waters anywhere from ten to twenty feet above the typical flood stage. 400 people died and there was about $500 million in property damage. If the flood had occurred only a few months later, it may have wiped out any cicada broods scheduled to come out of the ground.
- There was a massive F-4 tornado on June 23 and 24, killing 66 people in Shinnston and Harrison Counties. Two other tornadoes left the eventual death toll at 104. This kind of natural disaster can disturb the soil where cicadas live by unearthing trees.
- A rare — and powerful — earthquake struck Charleston in 1886, but its effects could be felt hundreds of miles away. It was about a 7.0 quake, and caused millions in damages. This is another natural event that can disturb the soil and damage cicada cycles.
- Hurricane Hugo made landfall in the Southeast United States in 1989, doing tremendous amounts of damage in the process. Wind and flood damage in Virginia left schools closed for weeks, even though it had weakened significantly during its transition from the southern states to those in the north. This type of event can offset cicada cycles if it occurs early enough in the year — and some do.