Non-biologist me suspects this is a case of 4n+1; an initial year, then an "emerge! fly away! party like it's spring break in Ft. Lauderdale!" signal with peaks

Non-biologist me suspects this is a case of 4n+1; an initial year, then an "emerge! fly away! party like it's spring break in Ft. Lauderdale!" signal with peaks every four years and the biggest peak during the 3rd (13 year) or 4th (17 year) cycle. (There are also two- to eight-year species, but I'm not finding any references to an 11-year species). Broods have stragglers that are usually off by 1- or 4-years from the main body. [1] The benefit would be that above-ground predators are overwhelmed during mating season. [2] Since adults eat very little, almost all resource consumption occurs during the underground phase, when all species and broods are feeding at the same time. Since it's not a resource issue then there's no benefit to avoiding emergence in conjunction with another species or brood. Theoretically it would help overwhelm predators even more, but there's probably little practical benefit to 17x (one species) vs. 34x (two species). What you don't want is a different brood every year; that would eliminate the feast-or-famine problem for predators. The timing between broods is just a random walk. Assuming stragglers are due to environmental or other non-genetic happenstance (4-year multiples are very strongly conserved), then if stagglers happen to survive one year their descendants would establish a new brood baselined 1- or 4-years offset from the original. Such straggling and establishing of new broods would obviously be very helpful in avoiding a species disaster during a bad year. [1] https://cicadas.uconn.edu/stragglers/ https://cicadas.uconn.edu/stragglers/ [2] https://en.wikipedia.org/wiki/Cicada#Life_cycle https://en.wikipedia.org/wiki/Cicada#Life_cycle (third paragraph)