Daily Change of Foraging Populations in Same-aged Groups of Honeybee Workers (Preliminary Report)

Up to the present no quantitative estimation has been carried out of the foraging population in honeybee colonies. Nevertheless, the problem is very important both from a scientific and a practical point of view. As a preliminary approach to this problem, the daily change of the foraging population in same-aged worker bees was traced by continual observation of individually marked workers in well-sized colonies from their emergence to death in different seasons. The results obtained are as follows. 1. The mortality curves uniformly showed a sigmoid trend in different seasons and colony sizes, with the modes at 25-30 days after emergence. Most of the marked bees disappeared 45 days after emergence. 2. Potential foragers appeared 10 days after emergence and attained the maximum absolute number at 20-30 days. Thereafter, the ratio of potential foragers to the total population of marked bees still increased for a while, but the absolute number of potential foragers began to decrease in parallel to the decrease of the total population of marked bees. 3. Within the range of colony size adopted, no clear difference in foraging population was present between strong and weak colonies. On the other hand, the difference according to the abundance of nectar flow was remarkable. In the season of heavy nectar flow, the foraging population increased very rapidly and was far larger than in any other season both in the absolute number and the ratio to the total population of marked bees. 4. The ratio of workers the foraging trips had been actually detected to the potential foraging population fluctuated from day to day accordings to weather conditions. If the activities under adverse conditions are ignored, however, it is presumed that about 80% of the potential foragers may have foraged actually every day. The number of pollen foragers also varied considerably, but seldom exceeded 50% of the total population of actual foragers.