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Water foraging bees in a desert collect water up to 2 km from their colony, and have consistent crop filling and flight times. They leave their colony and arrive at the water source with less than or equal to 1 mg sugar in their crops, which they dilute at the water source by collecting about 40 mu l of water, In 500 m flights back to the colony, radioisotope studies show they pass almost no crop contents to their midgut. If prevented from entering the colony for 15-36 min, they do pass about half of their crop contents to their midgut, probably when hemolymph sugar levels become very low. This water is rapidly absorbed from the midgut to hemolymph, and then is apparently rapidly excreted to the rectum via the Malpighian tubules and defecated, In this process the bee absorbs and excretes a volume of water at least as great as her entire hemolymph volume in a relatively short time (less than or equal to 20 min), The return flights of water collecting bees are normally fueled from sugar reserves in the bees’ bodies, and these reserves limit water collection to within a few kilometers of the colony. This limitation probably affects dispersal and density of honey bees in arid areas. Copyright (C) 1996 Elsevier Science Ltd