They encountered sweat bees (drawn to sweat, of which there was surely an abundance, and called - horribly - ''eye lickers'' in Brazil), vampire bats that transmitted lethal protozoa, malarial mosquitos, maggots that infected open wounds, electric eels that sizzled the horses and dogs they had with them, fire ants, piranhas, poisonous vipers, poisonous ants, termites, caymans, trees with poisonous sap (the curare tree comes to mind) poisonous frogs (the poison dart frog) and leg-eating mud-holes. (I can vouch for the latter, having stepped in one near a lily pad lagoon. It took two people to pull me out. Fortunately the mud hadn't gotten above my boots. Yup, another reason to wear boots.) In ''The River of Doubt,'' about Teddy Roosevelt's Amazon expedition, author Candace Millard adds: ''The rain forest was not a garden of easy abundance, but precisely the opposite: Its quiet, shaded halls of leafy opulence were not a sanctuary, but rather the greatest natural battlefield anywhere on the planet, hosting an unremitting and remorseless fight for survival that occupied every single one of its in habitants, every minute of every day.'' Whew.