I also watched...and yes. they could not find their son (Robert?) when the flood came. So, since it was so many years ago, that boy could be all grown up now, right?
All those people, some returning from 100 years ago. Egads.
As to those bugs, when this series first started I made mention of "the Pod people". Old movie wherein aliens were taking over the bodies of humans, and when they had, there were pea pods on the floor or somewhere. The movie was called "Invasion of the Body Snatchers".
So...all those dead bugs could be something similar. They are all coming to Arcadia, arent' they? And the bugs are right outside the city limits.