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."
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 left 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 -