17-year locusts and evolution

An obvious evolution question has just now shown its face again for the first time since 1987. Okay all you evolutionites out there:How exactly did the 17-year locust "evolve"?

It's really hard to picture something like that evolving.My own GUESS would be that the 17 year locust was originally designed as a signal of some sort, i.e. as a sign for some recurring event or celebration at 17-year intervals. I mean, if some biting fly or mosquito came out every 17 years you might figure it to be a microevolutionary adaptation but the locust is decorative like butterflies.

I may be mistaken and I went looking for where I might have read about it in my library but I believe Gould had a theory that the 17 yr. locust rythms has to do with the lifespan of the locust predators. That they evolved to take advantage of the shorter lifespan of the predators. Something like say some predator has a 15 year lifespan, and during this lifespan the locusts appear once, or possibly not at all. It may be a good food source but if it only appears once in the predators lifespan, there are better and more available foods out there.

That's an interesting idea but predators of an insect like the locust would mainly be birds with lifespans well under 17 years and, since the things seem to spend a lot of time at low levels, also dogs, cats, and anything else which eats insects and there'd be various lifespans in that mix.