Killer wasps of Saint Helena

12 August 2008

How does a common wasp become a 'killer' wasp? By travelling thousands of miles around the world to invade a new land, it does.

The common wasp, Vespula vulgaris> , lives in the northern hemisphere, in Europe, Russia, Japan and North America. So the last thing a scientist would expect to find are specimens in samples collected from the island of Saint Helena in the South Atlantic Ocean.

That is exactly what happened to Natural History Museum scientist, David Notton. 'Saint Helena is a tiny, windswept and rugged island almost 5,000 miles from England,' says David. 'It is remote and unspoilt and an unlikely place to find the common wasp.'

'I was very surprised, therefore, to find two common wasps from two separate localities in Saint Helena. There was also a report of another one seen but not collected, so the wasp was certainly breeding on the island.'

How did the wasp reach Saint Helena?

The common wasp is a well known 'tramp species' and has spread widely around the world. The queens can hitch a ride by creeping into packaging on cargo boats or airfreight. It has even reached as far as Australia and New Zealand and this is probably how it reached Saint Helena.

A friend to UK gardeners

As its name suggests the common wasp is common in the UK. It can be a friend to gardeners because it preys on many insect pests that feed on fruit, vegetables and shrubs.

In Saint Helena, however, it's a different story. Saint Helena has its own unique wildlife and the arrival of a new voracious insect-eating wasp would now put the native creatures under increased pressure.

Alarm bells

'An alarm bell started ringing in my head,' added David, 'because I remembered what happened when this wasp reached New Zealand.'

Common wasps have become a nuisance in New Zealand. They eat the native insects, which are not used to this kind of predation. They feed caterpillars, spiders, and other bugs to their larvae back in their nests.

Killer wasps?

David adds, 'These wasps are sometimes hyped in the tabloid newspapers as 'killer wasps' and the name is fitting, not because they kill people which is very rare, but because they kill thousands of other insects for food.'

As well as threatening rare insects with extinction, this also threatens the native insect-eating birds, as there is less food for them. The effect is worse in the milder parts of New Zealand where wasp numbers can build up over several years.

Unique animals of Saint Helena

'Naturally, I was concerned that the same thing might happen in Saint Helena, says David. 'This island has many unique species of insects, some of which the wasps might eat to extinction.'

'Some of the native plants depend on insects for their pollination. Also, the Saint Helena wire bird , a sort of plover, found nowhere else in the world, depends on insects for its food and could be threatened. To make things worse, the Island has a mild climate favouring the wasps.'

Averting an ecological disaster

As Saint Helena is a British Overseas Territory, the UK is responsible for helping the Saint Helena Government with nature conservation. To avert an ecological disaster, David notified colleagues who would let the Saint Helena authorities know about the problem.

'Right away, the authorities launched a campaign to alert the islanders and start eradicating the wasps,' says David.

'The campaign is continuing and with luck, the invasive common wasp will be wiped out on Saint Helena.'

'It will be good to think the native insects and the wire bird can continue to flourish in peace, thanks to the timely teamwork and expertise of the scientists of the Natural History Museum with the people, scientists and government of Saint Helena. '

Talk about bugs in the Bug forum

Have you seen a wasp you'd like to identify? Go to the Museum's new bug forum and discuss what you've seen.

You can add your own photos and get expert opinion from Museum scientists. There is also a gallery where you can try and identify bugs yourself.

Further information

External links