I do not know if research has borne this theory out or not.
This would have helped account for the widespread nature of the individual outbreaks, their intermittent nature, and possibly the association with rainy weather, which would accompany seasonal migration.
But, as far as I know, it is just a theory.
If there is some article which confirms it, and you have a link, please post it--I and others would like to read it as well. (thanks!)
If I hear any more, I'll let ya know.