By the time this paper arrives in mailboxes and stores, people in some parts of the country may have begun to hear the chorus of frogs that assures us that spring is coming. But most places will still be deep in winter. The frogs know this, and they have nothing to say. Not yet.  Fast forward a few months, though, past the thawing of the ponds and the outpourings of lusty frog song, which can be deafening to those who wander close, and past the equally prolific extrusions of eggs out of frogs and into ponds — fast forward past all of that to the moment when those eggs have hatched. Now. Imagine a pond in the middle of spring and the middle of the country teeming with life, roiling below the surface with little black jobs zipping to and fro. They seem to be made up of nothing but big heads and slim, powerful tails. Tadpoles. Pollywogs, if you will. Or, if you are in Honduras and trying to fit in, bunbulun. A young child arriving at a spring pond will delight in the sheer life force on …