Tag: Life Collections

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From pin to paper

Katherine Child, image technician in the Museum’s Life collections, doesn’t just use photography to capture the beauty of specimens. She is also an artist and has been trying out innovative techniques for her paintings. You may remember her amazing moth illustrations created with deposits of verdigris on pinned insects and she’s now using that technique to explore Museum staff’s favourite insect specimens.

Verdigris is a green corrosion often found on old pins within entomology collections (as well as elsewhere, on things like statues and copper pipes). Last year, after learning that the substance was once used as a pigment, I decided to try and make my own paint.

A clearwing moth before conservation, showing verdigris spreading where metal reacts with insect fats, or lipids.

Verdigris forms when copper or a copper alloy reacts with water, oxygen, carbon dioxide or sulphur. While a beautiful shade of green, the substance is damaging in natural history collections, where it can actually develop inside specimens and if left, split them irreversibly. So as part of the conservation of the Hope Entomological Collections, verdigris is removed.

I started to collect up the substance as it was cleaned from specimens and after about three years (you only get a little bit per pin) I was ready to make my paint! After my first moth project, the only question was, what to paint next…?

Attelabid_small
Byctiscus populi or ‘The Attelabid that changed my life’, chosen by Zoë (collections manager) who said ‘I saw a pink version of this species in the Natural History Museum in London and that’s when I decided I wanted to study entomology’.

With an estimated 6 million insects and arachnids in the entomology collections, it’s very easy to feel overwhelmed. You can pull open any one of thousands of draws and find astonishing specimens. While I have favourites, my first inclinations as to what to paint still felt a little arbitrary. After mulling over various possibilities, I decided to get help!

Chosen by DPhil student Leonidas, Agalmatium bilobum is a little bug which lays its eggs on tree bark, then covers them with mud to protect them.

I asked my co-workers what their favourite insects were, then opened the question out to regular volunteers and visitors of the Life collections. I loved finding out why people chose the things they did. Answers varied from ‘It was the first spider I ever looked at under a microscope aged 12’ to ‘Because they’re cool’ to ‘Because they have an ingenious way of manipulating spiders!’

Nuctenea_small
One of arachnologist Russell’s favourite spiders: Nuctenea umbratica. Though common in the UK, umbratica is Latin for “living in the shadows”, and it often hides away during the day. The slight transparency of the paint lends itself to a spider’s glittering eyes.

 

Painting this live African Mantis Sphodromantis lineola (chosen by conservator Jackie) was made slightly more challenging by the fact that the subject thought Katherine’s pencil might be tasty.

Most of the subjects I painted were based on specimens from the Museum’s collections or specimens individuals had brought in from their own collections, but one favourite was a live African Mantis, housed in the department to help with education and outreach. When I began to draw her she was intrigued by the movement of my pencil and came to the front of the tank, to follow every mark I made with her intimidating gaze.

A detail from the final painting
Attelabid that...
Katherine’s fabulous finished painting, which will be framed and displayed in the Life collections department.

Though time consuming, the painting was loads of fun to research and do. It’s fantastic to be surrounded not only by extremely knowledgeable people, but also by people with a genuine passion for what they do and a love for the insects (and spiders) they study.

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Why do we need pinned insect specimens?

Since we posted about ten-year-old Sarah’s amazing beetle discovery, we’ve had lots of queries as to why the insect needed to be caught and pinned. It’s a question we’re often asked, so here’s Darren Mann, Head of Life Collections at the Museum, to explain the value of ‘voucher specimens’.

The Museum’s collection houses over five million insect specimens, amassed over the past 300 years. This collection is, in effect, a biodiversity database, but unlike virtual databases, each data point has an associated ‘voucher specimen’ that was caught, pinned and labelled.

Although technical advances in digital macro-photography do reduce the need for some collecting, it is impossible to dissect an image to confirm an identification. So for many groups, even the best photograph in the world is inadequate for identification purposes.

Shingle CrawlerD18 (Psammoporus insularis Pittino, 2006) one of our few endemic insects.

Unlike plants and birds, many insects can only be identified with the aid of a microscope, to study tiny features that distinguish closely-related species. Some groups even require the dissection of minuscule genitalia to really tell them apart.

Entomologists take voucher specimens to enable this correct identification and these are later deposited in museum collections, making them available for further study in years to come. From an entomologist’s point of view, we believe we need to know what a species is, where it occurs and as much about it as possible, so we can inform biodiversity conservation.

The conservation assessment of UK insects by Natural England in their Species Status Reviews has only been possible with the data provided by entomologists, generated from collecting and identifying voucher specimens.

Entomologists follow a Code of Conduct for responsible collecting, which ensures they don’t remove too many species or damage the environment during their work .

There are numerous examples of the value and use of insect collections in contemporary science, including the discovery of previously unknown species in the UK and population genetics for butterfly conservation. Recently a species believed extinct in the UK was rediscovered. This was only made possible by checking the identification of several thousand museum specimens.

Museum collections also contain numerous examples of species now considered extinct in the UK. Without voucher specimens much of this research would be impossible and our understanding of insect distribution patterns, ecology and conservation would be significantly diminished.

Large Tortoiseshell butterflies, now considered to be extinct in the UK. The voucher specimens act as record in time of its occurrence in the UK.

What is rare?
Sarah’s False Darkling Beetle (Anisoxya fuscula) has been described as ‘rare’, but what does that mean in reality? For most invertebrates when we talk about a rare species we are not talking about a tiny number of individuals. This conservation status is based on their known distribution and the level of threat they face. A species can be rare if it is only found at one or two locations, but at those locations there may be many thousands of individuals.

The greatest threats to biodiversity are well known and include habitat loss, fragmentation and degradation and pollution, such as pesticides and light. Taking a small number of voucher specimens to confirm the identification of species has negligible impact on its population. But if we don’t know it’s there because we couldn’t identify it, then a housing development destroys its entire habitat… well you get the picture!

Further Reading
Ask an Entomologist
Entomological Collections
Natural England Species Status Reviews
To Kill or Not to Kill That is the Question Part 1
To Kill or Not to Kill That is the Question Part 2
To Kill or Not to Kill That is the Question Part 3
– Austin, J. J., & Melville, J. (2006). Incorporating historical museum specimens into molecular systematic and conservation genetics research. Molecular Ecology Notes, 6(4), 1089-1092.
– Colla, S.R., Gadallah, F., Richardson, L., Wagner, D., & Gall, L. (2012). Assessing declines of North American bumble bees (Bombus spp.) using museum specimens. Biodiversity and Conservation, 21(14), 3585-3595.
– Short, A. E. Z., Dikow, T., & Moreau, C. S. (2018). Entomological collections in the age of big data. Annual review of entomology, 63, 513-530.
– Suarez, A.V., & Tsutsui, N.D. (2004). The value of museum collections for research and society. AIBS Bulletin, 54(1), 66-74. Abstract available here
– Wandeler, P., Paquita, Hoeck, E.A. & Keller, L.F. (2007). Back to the future: museum specimens in population genetics. Trends in Ecology & Evolution 22.12, 634-642.

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Odd egg out

This is a great time of year to hear the distinctive call of the Cuckoo (Cuculus canorus) as it spends the summer in the UK. Collections Manager Eileen Westwig recently shared Cuckoo specimens with the public in one of our Spotlight Specimens sessions. You missed it?! No problem, here she is with the fascinating story of this threatened bird…

Cuckoos could be described as absent mothers, laying their eggs into the nest of a ‘host bird’, such as Dunnocks, Meadow Pipits, Garden Warblers, Whitethroats or Flycatchers. When she finds a suitable nest, the female Cuckoo will remove one of the host’s eggs and lay hers in its place. She lays between 12 and 22 eggs in a season, all in different nests. No worries befall her about building a nest, brooding out any eggs or raising her young as she leaves it all to strangers. One challenge for the Cuckoo is to make sure her trickery is not discovered.

When the female host returns to her nest, she will inspect it for any changes and if she discovers the intruder’s egg, she will simply toss it out. So the female Cuckoo has to be pretty good at forgery and mimic the host bird’s egg ‘signature’, copying the colour, pattern and shape of the original eggs. This is the only way to get away with her ‘brood parasitism’. Around 20% of Cuckoo eggs never make it. In the top picture, you can see the nest of a Garden Warbler with three Warbler eggs and one larger Cuckoo egg, on the top left.

An adult Garden Warbler (Sylvia borin borin) can reach a weight of 16-22g with a wingspan of 20-24.5cm

After twelve days, the Cuckoo hatches and pushes the other nestlings out. As the single remaining occupant of the nest, it has the full attention of the host parents, which try to feed a nestling soon outweighing. An adult Cuckoo is more than 6 times the weight of an adult Garden Warbler. The Cuckoo young will leave the nest after 19 days, but gets fed by the parents for a further two weeks. That is one busy summer.

OUMNH.ZC.11868_Cuculus_canorus_canorus_Eileen_Westwig
An adult Cuckoo (Cuculus canorus) can reach a weight of 105-130g with a wingspan of 55-65cm.

According to the RSPB, there are about 15,000 breeding pairs in the UK and Cuckoos are now included on the Red List, giving them the highest conservation priority. Ten years ago, numbers of this migrant bird fell by 21% and more than half of the population has disappeared in the past 25 years. Threats include damage to the bird’s winter habitats and a decline in large insect species that are its major food source.

Cuckoos migrate to West Africa over the winter months and can be seen in the UK from late March or April through July or August. Young birds leave a month or so later to give them time to grow and prepare for the long journey ahead. Wintering grounds are not exactly known but include Cameroon, Gabon and other African nations.

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Amour for armour

If you pop in to the Museum at 2.30pm on a Monday-Thursday afternoon, you’ll meet one of our Museum experts with some of their favourite specimens. Here Eileen Westwig, Life Collections Manager, shares one of her recent Spotlight Specimens.

Last month, as part of our regular Spotlight Specimens activity, I chose to highlight armadillo specimens. They got lots of attention, which is not surprising considering how amazing armadillos are. The word armadillo is Spanish meaning ‘little armoured one’. It is true that all armadillos have armour wrapping around their body as protection. Their size, however, varies a lot. The smallest one is the Pink Fairy Armadillo (Chlamyphorus truncatus), which grows up to 18cm (including tail length) and weighs up to a tiny 100g. At the other end of the spectrum, the aptly named Giant Armadillo (Priodontes maximus) is the largest, and can grow up to 150cm (head to tail) and weigh up to 60kg.

Giant Armadillo from the OUMNH collection. Sharp, big claws help to scratch and dig for food, such as tubers and termites, and dig burrows for sleeping.

Armadillos are found in South and Central America. However, the common Nine-banded Armadillo (Dasypus novemcinctus) has spread over the last hundred years, all the way into the southern United States. What makes it so successful is its varied diet of tubers, termites, ant larvae and other insects, as well as snails and bird eggs found on the ground. The expanse of ranching and the absence of natural predators such as cougars have made it easy for this long-nosed armadillo to spread as far as Texas and Florida.

Beside their stiff protective armour, all armadillos are capable of curling up their body to some extent, in order to protect the soft and vulnerable underside. Only one armadillo is the true champion when it comes to rolling up tightly into a perfect sphere. This astonishing achievement can be found in the Southern Three-banded Armadillo (Tolypeutes matacus). In the picture at the top of this page, you can see two armoured triangles in the middle, which are its head (on the left) and tail (on the right).

Common Nine-banded Armadillo showing its body plates, which usually lie underneath a layer of horn.

The armour of armadillos is made out of two layers. There are bony scute plates (visible in white in the picture above) that are overlaid with horny plates. The horny plates are made of keratin, the same material as hair and fingernails.

Nine-banded Armadillo made into a basket as souvenir

Sadly the existence of this amazing creature is threatened by loss of habitat and hunting. Not only are armadillos widely eaten, they are also made into tourist souvenirs, such as this basket.

According to the Centers for Disease Control and Prevention, some armadillos from the southern USA are naturally infected with the bacteria (Mycobacterium leprae), that cause leprosy (Hansen’s disease). Most people (95%) are immune to it, but please use caution if you’re ever in a position to handle an armadillo!

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Paint it green

In the process of researching or conserving old pinned insects, it’s common to find a green deposit clustered around the pin. This is known as verdigris and is a natural patina created when the metal oxidizes over time. Katherine Child is Image Technician in the Museum’s Life collections and takes photos of insects for researchers, students, artists and publications. She is also an artist in her own right, so when she witnessed verdigris being removed during a conservation project, she came up with an inspired idea.

A clearwing moth before conservation, showing verdigris spreading where the metal and the insect fats, or lipids, react.

A few years ago I read a book called Colour: Travels Through the Paintbox, by Victoria Finlay, and was interested to learn that verdigris was once used as a pigment. Verdigris, which I now know translates from French as ‘Green of Greece’, is a word that’s been in my vocabulary since I was small.  I loved its rich bright blue-green colour, which is often seen on old copper piping or copper statues.

Verdigris forms when copper or a copper alloy reacts with water, oxygen, carbon dioxide or sulphur.

L: Three years’ worth of verdigris, ground and ready to make into paint.
R: A second attempt at mixing the paint, this time using linseed oil.

As early as 5thcentury AD, it was used in paint-making, and until the late 19th century it was the most vibrant green pigment available. But it was unstable – Leonardo da Vinci warned that it ‘vanishes into thin air if not varnished quickly.’ These days synthetic pigments provide a more constant alternative.

Despite its past uses, verdigris is a big problem in pinned insect collections. Nowadays stainless steel pins are used, but pins containing copper still remain in old collections and these react with air and insect fats. The more fatty the insect, the more verdigris tends to form and, if left, it can damage a specimen irreparably.

Comprising around five million or so insects, the Hope Entomological Collections here in the Museum take quite a bit of looking after. A few years ago a project to catalogue and conserve many of its butterfly and moth specimens was undertaken and the removal of verdigris and repining of insects was part of this.

With paint-making in mind, I asked that the beautiful, but problematic, substance be saved.  About three years on I finally got around to using the pigment, which I had also been adding to while photographing the collections.

I chose a variety of differently shaped moths to paint (most of the verdigris came from moths, so moths seemed the most apt subject). To narrow my options further I went for green moths. Some of the specimens I chose had verdigris on their pin, so I was able to take pigment and use it to paint the very specimens from which it came!

Katherine tested out the newly made verdigris paint in her sketchbook.

After a first failed attempt to make watercolour paint (during which pigment and water remained stubbornly separate due to the greasy insect fats still present), I tried again, this time using linseed oil to make oil paint – and it worked! Traditionally a flat bottomed tool called a muller was used to press pigment into the water or oil. Not having one of these, I used the flat end of a pestle and a mortar which did the trick.

A Miscellany of Moths, the finished verdigris painting.

The paint went surprisingly far and, following on from the 14 green moths, I plan to use up the remainder to paint beetles.

Katherine’s Miscellany of Moths painting can be seen on display in the Museum’s Community Case until 18th October.