I’m not sure where the confusion about the phenomena of cicadas comes from. In fact, I imagine that many people, whether tongue-in-cheek or with bitter sincerity, would enjoy spending between two and seventeen years underground. Perhaps the confusion is born of jealousy. In any case, only one genus, Magicicada, spends over thirteen years underground. Most species have a much shorter lifespan. It is very important that the larvae spend this time underground. Why? Because they must mature into the instar, which is strong enough to tunnel from the earth and ready to moult into the adult from.
As for the screaming, it is more than understandable that after spending years underground, when confronted with the world above once again, one could be frightened enough to scream. However, I imagine that the original poster of that post confused human screaming with the cicada’s call. Only the males of the species have tymbals, the structure used to produce the call. Said call can reach up to 120 dB, roughly the intensity of large work equipment, or a firework. This call is not produced in anguish for the world, however. It can be used to signal distress, or for courtship.
It really is not that strange.
