Bumblebee life cycle: colony development

This page, and the pages linked from it show the yearly lifecycle of a bumblebee colony. You can either follow the lifecycle in chronological order by looking at all of the pages in turn, or you can skip to whatever part you are interested in by clicking the links below.

bumblebee nest, Bombus hypnorum nest, tree bumblebee nest seen from the inside

4. These two workers are either having a rest, waiting to go out foraging or guarding the opening. They will allow in workers who have "their" nest smell.

5. This is an opening in the wax cover made by a worker this morning.

6. I think this is a dead bee as it hasn't moved for more than 3 hours.

Unfortunately the live feed was cut shortly after I captured this image, so I don't know what happened to the nest.

This image was taken on the 9th of July from the live feed from the bird nest box at Ferndown Upper School in Dorset, England that was taken over by Bombus hypnorum, the Tree bumblebee. The nest is well established and seems healthy.

1. This round, knobbly object is the nest itself. Under this covering of wax will be the eggs, grubs, cocoons, queen, stores of pollen and nectar turning into honey. Not all bumblebees make a covering of wax over the cells, but in this case it is probably for protection.

2. This is a housekeeper worker. She will crawl around the nest clearing things up, performing repairs to the wax and taking out rubbish. Housekeeper workers are usually young and still secreting wax, or they may be deformed and unable to fly.

3. These two workers had just arrived back from foraging. They both have full pollen baskets - the pollen is the whitish blob on their back legs. They will go down to the nest and unload this pollen and possibly any nectar, then they will either have a rest or go off to work again.

The newly emerged bumblebee workers forage

When a new worker emerges her hair is silvery in colour and her wings are crumpled and soft. As you can see in the photograph below taken by Tyrone Williams.

Within an hour or two her hair dries and starts to change to the colours seen in foraging bees, and her wings will harden in about a day.

During this time she stays in the nest.

newly emerged adult worker bumblebee
Bombus lapidarius nest
Above a Bombus lapidarius nest. Taken from The Insect Societies, by E. O. Wilson, 1972. The Belknap Press, Harvard University. This is an excellent book covering all the social insects, and has a very good chapter on bumblebees. It should be available in any good library.

Bumblebee wax

Most of the wax for building cells is secreted from between the abdominal segments of the youngest workers. So, once the nest is established, the youngest workers tend to stay within the nest for the first week, performing household duties before emerging to forage.

However in a new nest the workers can start to forage after only two or three days, so this means that the queen can spend more time egg laying. In fact once the first lot of workers have started to forage the queen hardly ever forages. This may be because foraging is one of the most dangerous jobs in the colony.

Workers Make a mental map of the nest location

When a worker emerges into the light for the first time she memorizes landmarks to enable her to recognise the nest entrance. She does this by making a zig-zag flight over and around the nest entrance. She also navigates by the sun and has an inbuilt clock to compensate for the rotation of the earth.

Although Bombus terrestris is usually the first queen to emerge, it is quite often B. pratorum workers that are seen first as B. pratorum nests reach maturity faster than other species.

Bumblebee Life span

The average worker's adult life lasts about four weeks. In one study it was found that 29% of the workers died every 5 days (Brian, 1952). Bombus lucorum workers averaged 30 days (Brian, 1952), and B. terricola, a N. American species only 13.2 days (Rodd, Plowright & Owen, 1980).

A working life

This quotation is taken form The Humble Bee by Sladen (more info on the books pages), the most charming book I have ever read about bumblebees.

"The nest consists chiefly of workers, whose function in life is not to give birth but to labour for the establishment, bringing home and depositing in cells load after load of sweets (nectar and pollen), their only relaxation from this arduous toil being domestic work, such as tending the young, building the comb, and keeping the nest clean and tidy."

On the right is a bumblebee nest in loft insulation. This is a very common place to find a bumblebee nest, and it poses no danger to your house. All you need to do is leave it alone and when the nest comes to a natural end there will be just a few dead bees and a little wax left over. If you leave it still longer even this will be cleared away for you by the scavenging invertebrates.

bumblebee nest in a loft

 

Bumblebee Foraging preferences

Although a worker's life is short, during that time she will develop foraging preferences, This means she might prefer to gather her nectar and pollen from a particular species, shape or colour. of flower. Many flowers are simple disc shaped, e.g. like a daisy, and it is easy for any insect to get at the nectar and pollen. Other flowers are not so easy, and some are very difficult for the insect to get at the reward of pollen or nectar. The insect has to learn how to find the reward, and this takes time. So it makes sense that once the insect has found out where the reward is and how to get at it, she concentrates on that type of flower. Monkshood (Aconitum napellus) is a typical "difficult" flower, and it can be pollinated only by bumblebees; no other insect has the weight, strength and know-how to get inside it.

On the right the worker is foraging from a legume flower. These all have a similar construction. The bottom of the flower holds the stamen with the pollen attached. The nectar is located at the top, in this flower inside the green bit. So the bee must push open the flower to get at the reward. This is fairly easy for bumblebees as they are relatively heavy insects, but other insects may not be able to get at the nectar. As the bee pushes the flower open the stamens which have been held in the lower, fused petals spring loose and hit the bumblebee abdomen covering it with pollen. The bee gets the nectar reward, and as she visits the next flower some pollen on her abdomen will rub off on to the style of the flower and fertilise it - pollination!

bumblebee with ragged wings

Some bumblebees never leave the nest

Not all adults leave the nest to forage; some of the smallest workers may stay in the nest and perform "household" duties; these small workers may also have weak or deformed wings, but will probably live longer than the foragers and have less worn coats and wings, as they rarely fly. Workers can also exude wax for building cells to store honey and pollen, and the empty chambers that have held larvae are also used for storage.

Bumblebee Colony size

The size a colony reaches depends on the species concerned and the food supply, some can have as few as 30 bees, and Bombus terrestris can reach as many as 400. In physical size for a nest box this rages from a tennis ball to a shoebox. Most workers return to the nest every night, but some may spend the night outside sheltering under flowers as the males do. This can happen if there is a sudden change of weather in the evening and the bumblebee becomes stranded outside. The bee on the left had been out all night and was covered with dew when I took this picture. The reason she has a number is that I was recording which bees foraged on which flowers and needed a method of recognising individual bees.

Next, males and new queen eggs are laid>
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