The destination of blood, sucrose solution and, in some cases, water in the alimentary canal of adult bloodsucking dipterans is briefly reviewed. In Stomoxys calcitrans, structural development of the adult continues during the first few hours after emergence. Adults of both sexes, less than 2–3 h old, refused to feed on blood, sugar solution or water. Most flies took water or 10% sucrose solution when only 3 h old, and generally refused a blood meal when less than 12 h old, but a blood meal was taken readily when the fly was about a day old or older. Blood imbibed by flies from a warm blood pad was found primarily in the midgut, but some generally occurred in the crop, except in flies older than 54 h. More blood was found in the crop of younger flies. By contrast, when blood was taken from a human arm, it was never found in the crop but was present only in the midgut. Thus, in young flies, the mode of feeding affected the destination of blood. When water or 10% sucrose solution was imbibed, a small initial amount went to the midgut and the remainder to the crop. The amount of water ingested was always small, and flies which fed on water refused to take water again for 12 h or more. Large air bubbles occurred in the midgut of flies younger than 12 h, but disappeared thereafter. Flies feeding on a freshly prepared blood pad required twice as long to engorge as did those feeding on partially dehydrated blood, but those feeding on the human arm took 6 to 12 times as long as the latter. Digestion of blood took place in the posterior part of the midgut, and flies that had taken a previous sugar meal required a longer time to digest blood than those fed blood alone. The transfer of this sucrose solution from the crop to the midgut occurred while blood was being digested in the midgut. Our results are compared to reports on other bloodsucking dipterans.