To bee or not to bee

new horticultural trends in the uk have spelled bad times for bumble-bees, large insects belonging to the Bombus family. The bumble-bee population is declining; among Britain's 19 species of bumble-bees, only six boast a healthy population. Modern gardening practices with hybridised varieties of flowers have driven the bumble-bee to the edge.

The hybridised flowers look larger and have greater commercial use. But their nectar yield is little. This has meant loss of sustenance for the bumble-bees, who need large amounts of energy to fly as they are bulkier than honey bees. They store very little honey in the bee-colony and die in a matter of days without a steady supply of nectar ( New Scientist , Vol 154, No 2087).

Bumble-bees are not seen as the most valuable of the species. But contrary to popular belief, they are of immense economic importance. They are very efficient and irreplaceable pollinators with long tongues -- almost twice the length of honey bees -- capable of reaching even the deep seated nectar in crops such as red clover and field beans. They are better at warming up their flight muscles as compared to the honey bees and can fly even in cold weather.

Moreover, only bumble-bees can perform 'buzz pollination', the collection of pollen from flowers with inaccessible pollen tubes due to their peculiar swept back position. The bumble-bee clings on to the flower with its feet and vibrates its wings at twice the normal flying speed, which can be heard as the high pitched buzz. The flower gives away a puff of pollen that is stored in the pollen sacs in the bee's legs.

The process is very effective and Dutch tomato growers have set up bumble-bee colonies in their greenhouses to capitalise on the phenomenon. This has saved an annual cost of approximately us $21,800 spent on manually operated electric vibrators. Introduction of colonies of Bombus hortorum (the bumble-bee with the longest tongue in Britain) trebled the yields of red clover seeds in New Zealand in the early 1980s.

The most effective way to prevent the decline of the bumble-bee is gardeners and farmers choosing the right kind of plants. Flora For Fauna, a charity based at the Linnean Society, London, has been very active in drawing public attention to the plight of the bumble-bee. With financial backing from organisations like the Royal Society for Prevention of Cruelty to Animals, a programme called 'nectar trials' has been adopted for the past three summers. Students are encouraged to study the behaviour of the bees at the Botanic Gardens, Cambridge. Microcappilary tubes are used to measure the changing nectar yields of flowers.

It has been observed that bees prefer the older varieties of flowers. Modern artificially propagated flowers are attractive to the gardeners but incompatible with healthy seed production. Larger than their wild counterparts, they destroy the balance between the bee and the flower, making the nectar inaccessible. The bees were observed to tumble off the highly modified flowers.

Flora For Fauna has provided guidelines for farmers interested in tapping the immense natural resources that bumble-bees offer. As the structure and size of the flowers are important, local and native varieties should be preferred to the hybridised versions, advises the society. A list of varieties that are friendly to the bee has been drawn up. Flowers like nasturtiums are ideal as other bees can not reach deep into the flowers to collect the nectar. Other varieties like snapdragons are also recommended as no other species of bees can push open the flower and reach the nectar.

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