Wednesday, March 10, 2010

New Bumblebee Sightings in Scotland

Things may be looking up for bumblebees in Scotland. One rare and endangered species for that country, the Great Yellow Bumblebee, was seen farther south last summer than at any time in the past 30 years. This species has been declining for some time in the UK, and populations have been restricted to the far northern highlands and isolated northern islands of Scotland.

A possibly less auspicious sighting came early this year. The Southern Cuckoo Bumblebee (SCB) was spotted near the southern border of Scotland, a new species for the country. Previously the SCB has been common in the UK only near the southern coast of England.

Yes, it's a new bumblebee for Scotland, and a species that seems to be expanding its range rather than being in decline. But is this a good thing for bumblebees as a whole?

The questions arises because cuckoo bumblebees are parasites in the nest of other bumblebees. The normal bumblebee colony lives and grows by harvesting nectar and pollen from flowering plants. Most bumblebees have a number of special adaptations for pollen gathering, the most obvious of which is the presence of a wide, pollen gathering 'basket' on both hind legs.

Cuckoo bumblebees, on the other hand, have no pollen basket and make their living by invading the nests of pollen gathering species. The 'cuckoo' female takes over from the queen of the host species and begins to lay eggs. The workers of the host bumblebee then proceed to rear the cuckoo's eggs as though they were their own sisters. As a result the host colony rears no queens to carry on the next generation. All queens and males produced from that time on belong to the cuckoo species.

So you can see that a new cuckoo bumblebee is a mixed blessing. It can prosper only at the expense of normal bumblebee populations.

The ability to keep track of the gradual changes in UK bumblebee populations is possible largely because of the efforts of organizations like the Bumblebee Conservation Trust. Without a concerted effort to monitor pollinator populations, we are in danger of losing these critical components of our ecosystems before anyone has the chance to take action to save them.

Let's watch those bumblebees.

[The photo above is of the Great Yellow Bumblebee (Bombus distinguendus), taken by James Lindsay and made available under a Creative Commons licence.]

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