Webbing cloths moth — Tineola bisselliella

Moth damage.

Moth larvae on piano felt.

The humble clothes moth - Tineola bisselliella - is thought to be the number one insect pest in museums throughout the world. It is capable of destroying huge amounts of animal-based material. Amgueddfa Cymru is in the forefront of developing new methods in controlling this pest.

Know your enemy

In the past, museums fumigated collections regularly with large amounts of highly toxic insecticides to stop attacks. Modern methods of control try to recognise any problems early before any damage is caused - The key to good pest management is knowing your enemy.

The common clothes moth

The common, or webbing clothes moth, is a small shiny golden-coloured insect 6-8mm. long, often seen scuttling over infested material or fluttering around rooms somewhat aimlessly. The sole purpose of the males is to mate with the females (who do not fly), before dying.

The females then lay tiny eggs pushed in between fibres and hairs. It is the larvae that hatch from these eggs that cause the damage. They are able to digest keratin, which is found in fur, wool, feathers, hair, finger nails etc. As this is rather a sparse diet on its own, the clothes moth larvae prefer food that is stained or dirty, meaning that dirty woollen clothing is usually attacked as are the edges of carpets where a vacuum cleaner may not reach.

A protective silky web

The larvae protect themselves by weaving silky tubes where they live and feed. These silky cases give it the name webbing clothes moth. When the larvae are fully grown they will pupate inside these cases and after a few weeks the adult moths emerge.

The adults do not eat or cause damage themselves, but mate and start the life cycle all over again. On dirty wool in warm, moist conditions, two or three generations in a year are possible. With the humid climate of the UK and the centrally heated stores and galleries of museums, it is easy to see why the clothes moth is such a major pest.

Formerly in the Museum, the practice was to react after damage was found. Now the aim is to prevent the insects entering the Museum in the first place and to make it as uninviting as possible. Store rooms have well sealed doors and windows along with filtered air conditioning systems. As museums are public buildings, then some moths, be it as adults, larvae or eggs will inevitably be brought in.

A new generation of insect traps

Keeping an eye out for insects and insect damage is part of the conservator's routine work which includes carefully inspecting for signs of damage, and using traps. The Museum is in the forefront of developing a new generation of insect traps designed to catch specific species such as the common clothes moth.

These new traps are based on the power of sex. Females give off a scent, or pheromone - which can attract males from many metres away. This proves very effective for the moths in small areas such as cupboards and small rooms.

Traps are lined with a sticky adhesive along with a synthetic version of the clothes moth pheromone.

Insecticides as a last resort

If, despite all these precautions, moths still manage to attack material, we only use insecticides as a last resort. A major form of pest control at the Museum is to put the object in a plastic bag and place it in a deep freeze for two to three days, killing the insects, eggs and larvae without any damage to the object or toxic residues.

Through the combination of vigilance, good housekeeping and expertise, outbreaks of insect pests such as the common clothes moth are these days thankfully rare and dealt with rapidly.

Hypulus quercinus (Quensel), a rare saproxylic beetle collected at Dinefwr Deer Park

Ancient trees surviving in Britain's parklands contain many rare species of beetle that live on dead wood and fungi. Surveys of Welsh parklands by Amgueddfa Cymru found a number of species previously unknown to Britain.

Parkland and Deer Farming

Deer farming was introduced to Britain by the Normans. Many began as wood-pasture - open grassy areas with widely spaced oak trees - used for grazing animals and growing trees. These trees were pollarded (branches cut back to the trunk) in order to produce fresh new growth. This prolonged the life of the trees, supplied new shoots for animals to eat and also provided a plentiful supply of timber.

The best ancient trees in Europe

This way of managing British parklands over the centuries have resulted in them containing the best examples of ancient trees in the whole of western Europe.

Big, hollow, over-mature trees can survive for many hundreds of years. Along with many forms of fungus and lichens, these ancient trees support a large number of rare invertebrates (animals with no backbone) like beetles and flies.

The Ancient Forest

Nearly 700 species of British beetles, and a large number of other invertebrates depend on timber and fungi for their existence. These animals are known as saproxylics and would have been widespread before man cleared the original forest which once covered Britain.

In the last 200 years almost 20 species of saproxylic beetle are thought to have become extinct in Britain and some species are now amongst the rarest and most endangered British invertebrates. Only in established parklands and wood-pasture, where ancient trees were maintained, do these rare species manage to survive.

Welsh Parkland survey - the first of its kind

Welsh parkland sites had never been properly investigated to discover how important they were for the survival of saproxylic insects, until a survey in 1996 by Amgueddfa Cymru on behalf of the Countryside Council for Wales.

Species new to Britain

Over 350 species of saproxylic beetles and flies were discovered including some species previously unrecorded in Wales or Britain. The insect collection at Amgueddfa Cymru has been greatly enhanced by the addition of these new species. Three of the Welsh parkland sites investigated are probably amongst the top 20 sites in the United Kingdom in the diversity of saproxylic invertebrates they support.

A number of items in the collection of watches at Amgueddfa Cymru 'glow-in-the-dark'. The material that causes this glow (luminescence) is radium. As radium is radioactive, the watches in question now have to be treated with care, making their conservation, accessibility and display a big challenge.

Radium

1918 gent's wristwatch showing degraded and missing areas of radium paint

Marie Curie discovered Radium in 1898, and was the wonder of the new century - ironically thought to cure everything from arthritis to cancer. Mixing materials such as zinc sulphide and radium produces the glowing effect. In 1902, this luminescent material was first used to paint on the dials and hands of watches and clocks, allowing them to be seen in the dark.

Marie Curie eventually died from exposure to radium in 1934. Her notebooks, in which she was recording all her experiments are still too radioactive to handle today.

The Radium Girls

Glow-in-the-dark watches soon became popular with the mass market, and in the 1920s, production factories were set up where women would mix together glue, water, and radium powder into a glowing greenish-white paint that was then put onto the watches.

In order to paint neat and sharp numbers on the dials, the brushes needed a very fine tip. After a few strokes, the brushes would lose their shape, so the women "sharpened" the fine brushes by rolling the brush tips on their tongues to straighten the bristles, sometimes up to 6 times for every watch dial. Some even painted their teeth or applied glowing "makeup" as a novelty to show their friends. Many of these women would later die from cancer.

Testing for radioactivity at the museum

A radioactive contamination monitor (Geiger counter) was used to measure the radiation given off by the clocks and watches held in the collections housed at the museum. The highest readings showed dials to have a reading of 3000 counts per second against a naturally occurring level of 8 - 10 counts per second.

The measurable dose of Radium in a watch is apparently about 5 times the dosage from a standard chest X-ray.

The readings confirmed that the dials could be hazardous if exposure was not limited in some way. To combat this, the radioactive items were:

• Enclosed in a sufficiently dense material;
• Confined to a little used area of the stores;
• Warning signs displayed as to the nature of the hazard.

All objects containing radium that were on public display were identified and withdrawn and put into safe storage.

Radioactive Dust

Although the storage of these items can be controlled and managed properly, the conservation of these objects is of concern. Since the dials are anything up to 100 years old, the paint breaks down into dust resulting in an increased risk of contamination from exposure to the radioactive dust.

There is the possibility of breathing in this dust by carrying out work on the dials, such as working on the mechanism, cleaning the dial, hands or covers. As a result, all items in the Museum that pose a radioactive risk are handled with suitable precautions taken to prevent any harm done to the conservator.

Radioactive decay

Interestingly, tests show that the brightness of the dials is not related to the level of radioactivity. Even if the dial paint is dim or invisible in the dark, it could still give a high reading of radioactivity, since although the reactive luminous chemical might have broken down, the radioactive element, radium will continue to be hazardous for many generations to come.