Billions of cicadas are about to emerge from underground in a rare double-brood convergence
If it hasn't happened yet, it will do soon. The largest brood of 13-year locusts is about to emerge simultaneously with the mid-western brood of 17-year locusts - and even that only happens every 221 years.
The mathematically-minded will have noticed something about the periodicity of these insects - they are prime numbers (i.e. numbers that are only divisible by themselves and 1) ad there is a very good evolutionary reason for this - it makes it harder for a potential predator to synchronise with these emergencies because, since there are no periods that would coincide exactly with these primes other than the prime itself and a 2, 3, 4 or more period would only coincide with an emergence of these cicadas every 26, 39 and 52 years respectively for the 13-year locust, longer for the 17-year locust.
Because these broods only emerge in the same year, they form an effectively isolated genetic population and yet these two broods appear to be identical in appearance, song and genetics, so it will be interesting to see how they interact, although they occupy different geographical areas, so overlap is relatively rare.
As a strategy to avoid predation, this takes some beating in terms of
In the following article reprinted from The Conversation under a creative commons license, John Cooley, Assistant Professor of Ecology and Evolutionary Biology, University of Connecticut, USA and Chris Simon, Senior Research Scientist of Ecology and Evolutionary Biology, University of Connecticut, USA explains the significance of this event from the point of view of ecologists and evolutionary biologists. Their article has been reformatted for stylistic consistency: