Author: More than a Dodo

What’s on the van? – Bumble bee

This week’s What’s on the van? comes from Dr. James Hogan, of the Museum’s Hope Entomological Collections.

Bumblebees and honeybees busily working away are one of the iconic visions of summer. Bumblebees and honeybees are also closely related, both belonging to the order Hymenoptera, family Apidae.

In the UK 28 species of bumblebee (species of Bombus) have been recorded, although several species are sadly now extinct or have been seen only a few times.

The short-haired bumblebee (Bombus subterraneus) has been the focus of recent conservation efforts. Although extinct in the UK, descendants of some British short-haired bumblebees still survive– in New Zealand! These bees originate from a deliberate introduction to New Zealand in the late 19^th Century for pollination of clover crops. Unfortunately, attempts to re-introduce these New Zealand bees have been unsuccessful because they are too inbred, but by introducing short-haired bumblebees from Sweden the species is establishing again in Kent (more details about the short-haired bumblebee re-introduction can be found at http://www.rspb.org.uk/ourwork/projects/details/299380-shorthaired-bumblebee-reintroduction )

Although we have lost some species we have recently gained one more, the tree bumblebee (Bombus hypnorum). This species is believed to have colonised the UK naturally from France and since its arrival about 10 years ago is spreading rapidly across Britain. We first became aware of this new bee in Oxford in 2008 when Steven Williams, one of our regular volunteers, brought in a strange-looking bumblebee which none of us recognised. It had a colour pattern unlike any other British species, with a red-brown thorax and a black abdomen with a white tip.

After a bit of detective work (and some help from local bee expert Ivan Wright) the arrival of the tree bumblebee in Oxford was confirmed. This bumblebee is now a common sight in Oxford gardens –look out for it next spring!

What’s on the van? – Beryl gemstones

This week’s What’s on the van? comes from Monica Price, Head of Earth Collections.

This time, it’s a special double issue of ‘What’s on the van?’! Two gemstones, that look very different, turn out to be exactly the same mineral, beryl. On the right is a greenish yellow variety of beryl called ‘heliodor’. It gets its name from the Greek word for the sun, and is coloured by a trace of ferric iron. The stone on the left is absolutely colourless because it has no impurities colouring it. This kind is known as ‘goshenite’ after Goshen in Massachusetts, USA, where it was first found.

Beryl is composed of beryllium, aluminium, silicon and oxygen (Be₃Al₂(SiO₃)₆ to be precise) and it is not very common. Flawless transparent crystals are rare, and as they are also very hard and durable, they are ideal for cutting into gemstones. Heliodor and goshenite are not often seen in jewellers shops, and nor is the pretty pale pink variety called ‘morganite’. There are two kinds of beryl which are much better known, ‘aquamarine’ and ‘emerald’. Aquamarine is  coloured light blue or green by a trace of ferrous iron, while rare and highly prized emerald is vibrant green because it contains a little bit of chromium.

We talk about ‘cutting’ gemstones, but in fact the faces are ground away on a flat fast-revolving flat metal plate charged with abrasive powder, called a lap. The faces are then polished using finer and finer grades of abrasive powder. Each face is cut at a very precise angle to get the maximum amount of sparkle in the gem.

Our heliodor and goshenite gems are from a beautiful collection generously presented to the Museum by Mr Bernie Peel in 2004. You will be able to see lots more cut stones from the Peel collection in the Museum’s gemstone display when the Museum reopens in February 2014.