Vespa velutina is a social Hymenopteron, the colonies are organized with a division of the work based on three classes: queen, workers and males. The annual life cycle of Vespa velutina starts in spring: the overwintered gynes build a primary paper nest of the size of a tennis ball since April. In this first phase, the queen, alone, is responsible for building the nest, laying the eggs and feeding the brood.
When the first group of workers reaches the adult stage, the colony, including the queen, might build a new nest, often in a higher place and different position. This nest is generally called "secondary nest" and its foundation occurs in the period between May and June. This nest will host the hornet colony for the rest of the season until winter.
After the appearance of the first workers the queen starts to lay exclusively eggs. From this point on the workers get responsible of nest construction and enlargement and brood rearing; in addition they look for sugary substances to feed on and prey on other insects to feed the brood.
In fact, the adults need substances rich in sugars, so they are often visible near flowers and fruit trees. The larvae, however, are fed with protein substances, and that is why they prey on other insects, especially honeybees, that are abundant near the hives.
In one year, more than 10,000 individuals might rise from the same nest (up to 13,000 and an average of 6,000). The maximum number of individuals inside the nest is reached in October/November and it is at this time that the honeybees are most susceptible to predation by Vespa velutina.
Since September, the first reproductive adults appear, at first the males and then the future queens. The males mate with the new queens and then die. The nest will gradually be abandoned by just born queens that, once mated, will seek a place to overwinter. With the advance of the cold season the colony dies, and the life cycle and the life of the secondary nest of the yellow-legged hornet come to an end. The cycle starts again in the following spring, thanks to many queens surviving winter.