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.
Above 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!
Not all adult bumblebees 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.
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 shoe box. 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 above 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>