Differences in the Flowers Visited by Four Species of Bumble-Bees and their Causes

many countries and most observers are agreed that bees of each species tend to frequent different flowers but that there is considerable overlap nevertheless. The literature on this subject has been reviewed recently (Brian 1954) and will not be discussed again in detail. The object of this study was to determine what differences existed in one small area in the feeding plants of the four common species of Bombus present, and the cause of these differences. Many observers have commented on the connection between the length of the corolla tube of the flower and the tongue length of the bumble-bees that visit it but other factors also seem to influence the choice of flower by the bee. In many cases under natural conditions two or more of these factors may be confounded, for example corolla length and flower colour. In this paper an attempt has been made to determine the importance to bumble-bees of a number of these factors independently.