The cold weather is now upon us, and as the temperature falls, the bees form their Winter cluster, gathering around the small remaining patch of brood in the centre of the hive, in a tightly packed mass. Egg laying is now stopped and the bees enter a quiescent period. This is a time when the colony is vulnerable to pests such as mice. A mouse would not dare attempt to enter a hive during the Summer months when the entrance is well guarded by guard bees, but now the bees are tightly clustered, a mouse can easily creep through the unguarded entrance, and do untold damage to the comb and the valuable food stores. A mouse guard is therefore placed across the entrance, allowing the bees to emerge on a Winter's day to take cleansing flights, but keeping mice out. This is kept in place until the next Spring, when the bees will start foraging again and guards will once again take up their duties at the entrance.