The 4 stages in the life cycle of a bumblebee colony
Male (unfertilised) eggs
are laid and worker larva develop into queens
The bumblebee queen can
lay two types of egg;
- fertilised eggs with chromosomes from the queen and a
male she mated with the previous year. These eggs become either workers or queens.
- unfertilised eggs which contain
chromosomes from the queen alone. These eggs become males.
The sperm from the mating is stored in a small container called a spermatheca located in the queen's vagina. As the queen lays the egg she decides whether or not to fertilise it with sperm. The fertilised eggs develop into workers
(females), and the unfertilised eggs develop into males.
The queen lays
unfertilised eggs only towards the end of the colony life. After she has laid
male eggs she may lay fertilised eggs that will become queens, but she will not
lay any more eggs that will develop into workers, so the laying of male eggs
signals the start of the end of a colony.
Bumblebee workers can lay unfertilised eggs
At about the same time as the
queen starts laying unfertilised eggs that will produce males, the ovaries of
some workers, usually those performing household duties, may develop. It is
possible for workers (without mating) to lay unfertilised eggs that will
develop into males, however workers cannot produce queens or other workers.
Some workers try to lay eggs of their own, and may even attempt to eat eggs
laid by the queen. This leads to aggression between worker and worker, and
worker and queen. In many cases the more persistent workers will succeed in
laying some eggs that will reach maturity.