Records for the 5 summer months beginning May 1, of 350 scale colonies over a period of 23 yrs. show a single main nectar flow beginning approx. June 21, reaching a peak around July 18 and ending about the middle of August. During the 10-yr. period 1925-1934, about 58% of the main flow took place in July and 42% in Aug. From 1935-1944 81% of the flow occurred in July and 19% in Aug. The dandelion flow in late May and early June provides an important stimulating nectar flow. Package honey bees should be received in Manitoba before the middle of April to be strong enough to take advantage of the beginning of the main flow. A study of the nectar flow indicates that colonies to be overwintered should be requeened about the first week in Aug. Colonies which are to be destroyed should be dequeened around Aug. 3 to be ready for honey extraction about August 27. Southern queen breeders are advised to mark the thorax of each queen shipped with a bright color in order to facilitate locating the queen among the worker honey bees in a colony in the northern apiary.