Bombus terrestris is our largest bumblebee, and usually the first to emerge. The thing to note on the queen is the dirty orange colour of the hairs at the end of the abdomen (below), although on continental Europe and in the Channel Islands the tail of the queen is white. Also when Bombus terrestris and B. lucorum can be seen together the yellow hairs of B. terrestris appear more orangey while those of B. lucorum are more lemon yellow.
Workers (below) have a white tail, and are almost indistinguishable from Bombus lucorum workers.
Lengths, queen 20-22, worker 11-17, male 14-16. Bombus terrestris is one of the main species used in greenhouse pollination, and consequently can be found in many countries and areas where it is not native; Tasmania for example.
Slightly smaller than Bombus terrestris, and with a white tip to her abdomen. Lengths, queen (below) 19-20,
worker (below) 11-17,
male (below) 14-16.
Populations are believed to be declining.
The queens Bombus terrestris and B. lucorum are usually the first to emerge in the spring. B. terrestris queens are the largest bumblebees we have in the UK. It is fairly easy to differentiate between B. terrestris and B. lucorum queens -
The workers of both species look like smaller versions of the lucorum queen. See the worker on the left. They are almost impossible to tell apart without dissection. The size range can vary quite a lot, but usually the smaller workers are from the earliest laid eggs. Bombus lucorum workers weight range from 0.04 - 0.32 g and the queens from 0.46 - 0.70 g; B. terrestris workers range from 0.05 g - 0.40 g.
The males have a many more yellow hairs (see the photograph near the bottom of the page), and a distinctive yellow nose. Of course they do not usually emerge until about August.
Both of these species make their nests in the ground, usually in old mouse or vole nests, and in the U. K. preferably facing south to keep the nest warm, though B. terrestris tends to prefer shadier sites.
Generally the nests of B. terrestris have a deeper and longer tunnel that those of B. lucorum. Tunnels of 2 metres long have been recorded. A favourite nesting site of B. terrestris is under garden sheds. Successful nests can have as many as 350 workers.
In the early days of the nest it is estimated that a Bombus terrestris queen may have to visit as many as 6000 flowers per day in order to get enough nectar to maintain the heat needed to brood her eggs (for more about this most difficult time in a queen's life see the lifecycle pages). And during every foraging trip the brood will cool down, so the trips should be short. This is why it is vital that the nest is located close to rewarding flowers.
The cuckoo species of B. lucorum is B. bohemicus, and the cuckoo species of B. terrestris is B. vestalis.
The queen secretes a pheromone, which, if present within the first 5 days of larval life determines that the larva will develop into a worker. If the pheromone in absent, and if the larva receives sufficient food (more than a larva destined to be a worker) during her final instar she will develop into a queen. Consequently a queen larva is larger than a worker larva. It is believed that caste determination works in a similar way for other bumblebee species too.
The photograph below shows the pollen basket of a Bombus terrestris queen - it is the yellow blob on her leg.
Below the basket is shiny and empty, while above it is partly filled with yellow pollen.
The pollen basket is the modified tibia of the hind leg. The inside leg is covered with hairs to rub pollen off the body. This is then passed to the pollen press, which is formed by a comb on the tibia, and the press or auricle on the metatarsus. The levering action of these two press the pollen, and it is pushed up onto the shiny, flat or convex tibia. The surrounding hairs are stiff and hold the pollen safely until the bee reaches the nest.
Both species have comparatively short tongues for bumblebees, so they tend to forage on flowers with short corollas and daisy-type flowers. However they are accomplished nectar robbers.
All bumblebee males patrol mating circuits laying down a pheromone to attract new queens. The pheromone is used to scent-mark prominent objects (tree trunks, rocks, posts, etc) on the circuit. The circuit is marked in the morning, and after rain. The scent of some species can be detected by some humans. Usually they patrol at species specific heights. Bombus terrestris and lucorum males patrol at tree-top height. However this depends on the habitat.
The Bombus lucorum male below was found dead in July. The tip of one of his antennae is missing, but apart from that and some disarray to his wings, he was intact.