Under the Microscope: The bumblebee is possibly the most familiar flying insect in our gardens and we instantly recognise its little, squat, hairy, striped body as it buzzes busily from flower to flower.
People tend to be especially wary of the bumblebee because of its large size and loud buzz, but this bee is far less aggressive than the honeybee and generally will not attack a human unless its life is under threat. The bumblebee is one of nature's hardest and most harmless workers and is beneficial to humans and plants alike. Unfortunately the bumblebee is under threat from modern agricultural practices (www. bumblebeeconservationtrust. co.uk)
The gentle, slow bumblebee is a distant cousin of the honeybee. Like the honeybee, the bumblebee feeds on nectar and gathers pollen to feed its young. Britain and Ireland have 25 native species of bumblebee. Three native species have gone extinct and 15 are under pressure.
The UK countryside was once a patchwork of mixed farmland full of wild flowers rich in pollen and nectar and grass meadows where bumblebees could nest in summer and hibernate in winter. Intensive farming puts most pressure on the bumblebee, causing loss of habitat, which provides food and nest sites for the bees.
The bumblebee is of great importance to agriculture, horticulture, and general biodiversity because of its role in pollination, ie the process whereby pollen, the plant equivalent of sperm, is transferred from the male parts to the female parts of flowers to fertilise the egg cells that then develop into seeds. Bees travel from flower to flower, gathering pollen for food, and inadvertently transfer some pollen, which sticks to their bodies, to the female flower parts. The bumblebees are major pollinators of clover and wild flowers and if they die out these flowers may also vanish which could have catastrophic effects on other species that depend on them.
The commercial importance of bumblebee pollination is enormous. For example, broad, field and runner beans and raspberries are very dependent on the bumblebee. Specially bred bumblebees are also deliberately used to pollinate commercially grown tomatoes.
The conservation of the bumblebee is essential. Bumblebee nests can be large (up to 400 sterile workers) and each bee travels more than 1km from the nest in search of suitable flowers. Individual bees locate good feeding areas by observing where other bees feed, unlike the honeybee, which passes on this information to its companions by doing a complicated dance in the hive. Each nest requires several hectares of suitable flower-rich habitat to support it. Therefore, in order to support a viable population of bumblebees in the long term, large areas of land must be managed sympathetically.
A UK initiative to help save the bumblebee has been launched by Syngenta, the international agribusiness committed to sustainable agriculture. This develops field margins into clover-rich areas that provide the bees with vital food resources rich in pollen and nectar. These margins can be created with little loss in overall field output. Results to-date have been encouraging. Other initiatives to be encouraged are the replanting of hedgerows and the recreation of hay meadow and chalk grassland habitats.
The life cycle of the bumblebee is as follows. In autumn the young mated queen bees seek a place to hibernate for the winter. In spring the queen locates a suitable place to build her nest. She busily gathers nectar and pollen to turn into honey and feed her newly hatching brood. She lays her eggs, about six at a time, and eventually they develop into fully grown female worker bees that begin to work to support the colony and the queen. The queen continues to lay eggs, spending her whole time in the nest, and the pollen and nectar collection is delegated to the workers. This continues through late spring and summer until the nest has reached the right size for the species.
The queen now lays eggs destined to become next year's queens as well as male drone bees. The only function of the drones is to mate the young queens to ensure next year's colony. The drones leave the nest but the young queens remain. When the first sharp drop in temperature occurs in late autumn, the old queen, the workers and the drones die. The newly mated queens hibernate over winter to start the cycle again in spring.
Most species of bumblebee have a black body with yellow stripes. They appear and feel fuzzy because of soft hairs that cover the body. The queen and the worker bees can sting, but the drones cannot. The sting isn't barbed, as is the sting of the honeybee, so they can sting more than once.
For many years, physicists were deeply puzzled by the bumblebee's ability to fly. It didn't seem to be possible based on the animal's size, shape, weight and wing capacity. However, more recent aerodynamic analysis satisfactorily explains why the animal can fly. Bumblebees are not commercially valuable as producers of honey. Because the entire colony does not over-winter, they do not need to stockpile honey and are therefore not important as honey producers.
Bumblebees are found in higher latitudes that range from warm to cold climates where other bees might not occur. The bumblebee is one of a few types of insect that can regulate its body temperature through incoming solar radiation and internal mechanisms such as shivering and cooling from the abdomen.
William Reville is associate professor of biochemistry and public awareness of science officer at UCC, http:// understanding science.ucc.ie