The Defence of Bumblebee Colonies

I. A study has been made of the ability of bumblebees to recognise intruding bumblebees from other colonies and of their behaviour towards them. 2. Bumblebees are to recognise intruders by their scent alone. Scents of strange colonies may be adsorbed onto the body surfaces of bees causing them to be attacked when they return to their own colony. It is suggested that the similar body odours possessed by members of the same colony arise partly by adsorption of the odours of their nest by the waxes on their body surfaces. 3. Large colonies have guards at the entrances of their nests. Some bees act as guards for several days in succession, and periods of guard duty alternate with periods of foraging and nest duties. 4. Certain bees in small colonies are more ready to attack intruders than others. The aggressiveness of such bees is probably associated with the relatively high degree of development of their ovaries. The aggressiveness shown by queens towards each other can also probably be explained in this way.