Why Do Periodical Cicadas Die Simultaneously After Emergence?

[Vanadium 50]

Fermilab has been hit by the every-17-years plagues of periodical cicadas.

Two days ago, the noise was deafening. Yesterday it was quieter. Today you need to struggle to hear one or two. Dead ones litter the ground.

Why do they die at the same time? Emergence took 4 or 5 days. I would expect them to die on a somewhat longer timescale.

 

[Flyboy]

If they all emerged on the same night, they should have similar lifespan aside from a few stragglers, as they don’t feed. The annual cicadas live much longer because they actually feed on trees and plants during their several weeks above ground. (And the occasional attempt to feed on humans who try to admire them in their hand. They realize pretty quickly that you’re not a tree and buzz off.)

 

[Ibix]

Is it possible they emerged over a day or so and lived a day or two? Particularly if the distribution of the survival times is skewed to the right (likely) there'd be a fairly sharp peak in population after a day or so when they're all hatched but haven't started to die yet, then a (comparatively) slower fall off until you've only got the longer-lived late-hatchers.

(Obligatory "git off o' my lawn" at the last stragglers.)

 

[Vanadium 50]

At the risk of getting all mathy, I'd expect the variance in dying to be equal to the variation in emerging plus the variance in adult lifetime (which might be zero).

But it seems that the variance in dying is smaller than the variance in emerging.

 

[berkeman]

Why do they die at the same time? Emergence took 4 or 5 days. I would expect them to die on a somewhat longer timescale.

I have a theory -- Broken Heart Syndrome:

https://www.mayoclinic.org/diseases-conditions/broken-heart-syndrome/symptoms-causes/syc-20354617

 

[Vanadium 50]

Well, it is true that like most 17 year olds, they have just one thing on their minds.

 

[russ_watters]

At the risk of getting all mathy, I'd expect the variance in dying to be equal to the variation in emerging plus the variance in adult lifetime (which might be zero).

But it seems that the variance in dying is smaller than the variance in emerging.

Maybe they are easier to count when lying on the ground vs flying in the air or sitting in a tree?

 

[Bandersnatch]

I was just going to say. The experimental setup here is atrocious. The half-hearted attempt at statistical analysis is neither here nor there when you're going by ear and memory.
If only that Vanadium guy was here, he'd give you a stern and brusque, but ultimately educational, talking-to for trying to draw conclusions when you don't even know if you have any data.

 

[pinball1970]

A mayfly lasts about a day too. Genetic programming. What I find more interesting is that their emergence are based on primes.

 

[Vanadium 50]

It is true I have not done statistics. The effect on sound is real, if unmeasured. If you do not live in an area where these bugs live (hemiptera, so "bug" is appropriate) you have no idea how loud they can be.

It's also not a bug or two. It's a couple bugs per square meter. Maybe even one per square foot in places.

They are not mayflys. Their life cycle is (I am told) ~4 weeks as adults. My puzzlement is that the lifetime seems anticorrelated with emergence time - the ramp down is faster than the ramp up.