The Bombus Bee

Bumblebees are social insects,  there is a certain level of interrelation between individuals of the same colony. The latter is divided into a number of groups, each with a specific task. At the top of the hierarchy stands the queen, that does not differ physically from the workers except for its size which is much bigger than the size of the largest worker.

The earth bumblebee, Bombus terrestris, is the most common of three species found in Israel. It is located in Mt. Hermon, upper Galilee, lower Galilee, and Mt. Carmel. The body of B. terrestris is covered with black hairs and two stripes of yellow-brown hairs, one on the prothorax, and the other on the upper part of the second abdominal segment. The tip of the abdomen is covered with white hairs. The head is relatively small; its length does not exceed its width.

The size of the queen bumblebee ranges between 20-23 mm in length and  38-43 mm wing span. The average size of a worker bee ranges between 11-17 mm in length and 22-34 mm wing span. The male, who has similar coloring to the workers and queen,  is between 14-16 mm in length and has a wingspan of  30-33 mm. As opposed to the queen and workers, the male does not sting. 

LIFE CYCLE CHART OF THE BUMBLEBEE

(a) In the spring, the queen leaves her hibernation place and goes in search of a suitable nest.

(b) In the nest, the queen prepares a storage place for the honey, gathers pollen together and lays the first eggs upon it.

(c) She feeds the larvae and keeps them warm until they pupate into workers.

(d) After the birth of the first workers, the queen concentrates increasingly on laying eggs, while the workers take on the tasks of feeding the larvae and collecting food.

(e) The colony increases in number and the newcomers increase in size.

(f) Ultimately new queens and drones are born, by then the old queen is usually dead.

(g)The young queens mate and go in search of a suitable hibernation place.

The Life cyrcle of the Bumblebee in nature
In springtime, the mated queen leaves her hibernation harborage and seeks out a nest site. In the nest, the queen builds a thimble-shaped beeswax honeypot in which she stores nectar. Nearby she forms a lump of field-collected pollen, excavates a depression in it and lays one or more eggs in the depression, covering it with wax.
The eggs hatch and the larvae feed on their bed of pollen. As they grow, the queen opens the wax covering and adds more pollen and nectar. She perches on the brood clump, incubating the larvae to speed their development. The larvae mature and each spins a cocoon of silk in which it pupates and completes development into an adult.
After the new workers emerge, their empty cocoons are used as storage pots for honey or pollen. More pollen lumps with eggs are deposited alongside or on top of the old ones, and thus the irregular comb grows. Eventually there are enough worker bees to do the foraging and housekeeping tasks. The queen concentrates on laying eggs.
The colony peaks to a few hundred individuals.
The colony switches from producing female workers to producing males and new queens,  sometime in mid- to late summer.
The males leave the nest a few days after emerging. The new queens mate with the males. The old queen dies before winter.
The new mated queens leave the nest and seek out a suitable overwintering site where they will stay throughout winter.

The life span of the queen ranges between 12-24 weeks (18 weeks on average), beginning from the moment she starts to lay eggs. The development time from egg to adult is 3-4 weeks. The life expectancy of a forager bee is about 3 weeks, which brings the total life cycle of such a worker to about 7 weeks. A worker bee which spends all her time in the nest is capable of living up to 12 weeks.