Tag Archives: natural sciences

Object of the Month – June 2023

This is the cast skin / exoskeleton (exuvia) of a dragonfly larva, found in Elsenham in August 2005. The shape of the eyes and the length (40mm) suggest it’s a hawker dragonfly, while the finder’s description of the adult dragonfly being green and yellow means it is probably a southern hawker, which are common in July and August.

Dragonfly exuvia © Saffron Walden Museum

These dragonflies spend 2 or 3 years as a larva, or nymph, living underwater, before coming above water to shed their skin and emerge as an adult.

Southern hawker dragonfly by Tom Wiersma, via Wikimedia Commons.

Dragonflies, like all insects, have a hard exoskeleton which does not grow with them. After hatching from an egg, dragonfly nymphs gradually grow into adults through a series of moults to shed their skin, which allows it to grow in size each time, emerging as an adult directly from the last moult.
The nymphs look similar to the adult, with a long body and six legs. Nymphs in the last stages of growth have wing buds that you can see on this specimen.
This method of growth, through nymphs with wings developing on the outside, is called incomplete metamorphosis.

This is different from other insects including flies and butterflies, which hatch as maggots or caterpillars. This is the larva of the insect, and it looks very different from the adult. The larva in these insects also has to moult to increase in size, but the final moult is different. It creates an inactive pupa (called a chrysalis in butterflies) where the final radical transformation into the adult takes place. This method of growth from larva to pupa to adult is called complete metamorphosis.

Visit the Museum to learn more about the two types of metamorphosis in the Discovery Centre, and take a closer look at two exuviae from our Malaysian stick insects.

Exuvia of female Malaysian stick insect © Saffron Walden Museum

Exuvia of male Malaysian stick insect © Saffron Walden Museum

Image credit:
Female Southern Hawker – Tom Wiersma, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons. Accessed 25.5.2023.

Valentines in our collections

A bit of Valentine’s related history for February from our collections!

An invitation to a Valentine’s ball at Wimbish Village Hall, 12 February 1943. Miss McQueen was well-known locally she had a small farm at Rowney Corner from which people could buy fresh eggs and she also played the organ in the 1970s at the church in Wimbish.

We also have a selection of Victorian Valentines cards. These 19th century designs typically include floral decoupage, lace doilies, ribbon details and lace trimmings. Inside the cards are lovely little poetic verses.

In our Natural sciences collections we also have these amethyst gemstones associated with love and romance.

Amethyst is the birthstone for February, but as a symbol of love, St Valentine is said to have worn an amethyst ring so Christian couples in Ancient Rome could identify him. Valentine was a priest who carried out forbidden Christian marriages and married young couples, when the Roman empire persecuted Christians and preferred their soldiers to be unmarried men.

Lapis lazuli can represent truth and friendship, and in Christianity represents the Virgin Mary. With the blue of the sky and gold of the sun, it represents success in Jewish traditions, while beads found in the ancient town of Bhirrana from 7500 BCE are its oldest known use by people. The remains of Bhirrana are in the Indian state of Haryana.

Sapphires are popular for engagement rings, as used for Lady Diana’s engagement ring from Prince Charles. Sapphire is the traditional gift in the UK for a 45th wedding anniversary and can symbolise truth and faithfulness.

In Ancient Greece and Rome, the word sapphire was used for lapis lazuli, as sapphire was only widely known from the Roman Empire onwards.

Object of the Month – February 2023

A picture of a taxidermy common eider duck. It has a black cap to its head, a yellow beak, white head, neck and back and a black underside, with yellow legs and feet. Against a painted backdrop of a rocky mountain and hazy clouds.

This month we’re celebrating the Lost Language of Nature project, putting the finishing touches to this common eider. James and Charlotte have cleaned its plumage, repainted its beak and feet, and refreshed its base to help preserve it for future exhibitions.

Common eider mounted skin

Eider ducks are famous for their soft downy feathers which help keep them warm in freezing conditions. ‘Down’ comes from the Old Norse word ‘dúnn’, the word for the fluffy feathers of young birds and the same feathers which insulate adult birds. In adults, the down is hidden beneath the larger contour feathers which give birds their colour, patterns and shape.

A fluffy white feather on a black bacground

Down feather © Wouter Hagens, CC BY-SA 4.0, via Wikimedia Commons

These wild ducks can be ‘farmed’ sustainably for their down feathers, which are taken from the nests once chicks have fledged. This down is used to make traditional eiderdown pillows and quilts. In the UK, eider ducks are sometime called St Cuthbert’s duck or Cuddy duck, according to the belief that St Cuthbert’s holiness protected Farne island and its population of eider ducks.

Grassy and muddy ground wiht a grey nest of fluffy eider down. Three eggs are in the middle of the nest.

Eider nest © Paul Gierszewski (Gierszep), CC BY-SA 4.0, via Wikimedia Commons

Saffron Walden Museum wants to hear your stories about wildlife and nature in your life, or that you know from parents and grandparents, to help create more interesting, relevant and diverse displays in the future. Fill in a postcard in the Museum to join in or search online for ‘Lost Language Saffron Walden Museum’.

Learn more about this Object of the Month in the Museum throughout February.

Identification – Fossil sponge in flint

Some flints do contain fossils, or look like whole fossils. Fossils inside the flints are often sea urchins, or cockles or other small shellfish. Sometimes, the whole flint looks like fossil, and this may be because the silica that created it was forced into a hollow space in the hardening chalk filled by a sponge. The silica fills the gaps in the sponge’s skeleton, and over millions of years, the skeleton itself can dissolve away and be replaced by other minerals. This skeleton is a fossil, and the flint fills the spaces left by the soft parts of the animal after they rotted away.

A grey, funnel-shaped fossil on a wooden surface

Typical funnel-shaped sponge, fossilised in flint. © L Hodgson.

The shape of this piece of flint looks a lot like a small sponge that lived on the sea floor, and was fossilised in flint as the thick mud solidified into chalk. It may have patterns inside it that show the structure of the sponge’s skeleton. The wiggly line around the widest part of the flint shows the top rim of the sponge and the rough texture of the line is the surface texture of the sponge preserved as a fossil.

More info on flint and chalk in Essex in this post from 2020. https://saffronwaldenmuseum.swmuseumsoc.org.uk/identification-flint-fossil-sponge/

Object of the Month – October 2022 – Alpine Swift

Dark alpine swift (Tachymarptis melba) on a white perch

This month we’re celebrating the Lost Language of Nature project, with repair work to this alpine swift. This bird has been cleaned and had its base refreshed to help preserve it for future exhibitions, and will be on temporary display in the Museum throughout October. Alpine swifts spend the warmer months around the Mediterranean Sea and further east, or in southern Africa, and spend the cooler months in parts of east and west Africa. This one was found or killed in Hinxton, Cambridgeshire, in 1832. They are related to the common swifts we see in Britain but are noticeably bigger. Old beliefs about swifts said that they had no feet, and the scientific name of the common swift and related birds – including the alpine swift and hummingbirds – even comes from the Ancient Greek for ‘without feet’.

We’d love to hear your stories about wildlife and nature in your life – rhymes, songs, saying, or names for plants and animals that you know from parents or grandparents. Fill in one of our special postcards in the museum, or click here.

Anyone and everyone has a story to tell, and your stories will help us create more interesting and relevant displays for everyone who comes to the museum in the future.

Alpine swift after conservation work

Swift work

This alpine swift is 184 years old and needed a good clean with special smoke sponge to remove dust and dirt from its feathers. Conservation work like this is always done very carefully, trying to avoid harmful chemicals, and using techniques that can be easily reversed if needed.
We cleaned its glass eyes with rubbing alcohol (isopropyl alcohol) and a hand-made cotton swab. The dust and dirt on the feathers can allow mould to grow, which damages the feathers because it produces acidic waste products. This bird had some possible mould patches underneath its tail and on top of its right wing, which we also cleaned with rubbing alcohol to kill and remove the mould.

We removed the swift from its base to paint the base white – you can see green splashes on the bird’s feet where the base was painted green in the 1930s without removing it. Birds are attached to their stands using wires from the bottom of the feet, and we had to cut one to remove the base.

Underside of bird with feet upwards. Wire protruding from foot on left of picture.

Alpine swift removed from perch, wire on right foot cut.

A new wire then needed attaching so the bird could be put back on its perch. We wound green florist’s green wire around the cut wire underneath the swift’s foot, and secured the new wire to its leg using Japanese tissue paper and conservation-grade PVA glue like tiny papier-mâché.

Underside of bird with feet upwards. New wire protruding from foot incentre of picture.

Alpine swift removed from perch, new wire on left foot.

Object of the Month – September 2022

The Museum’s ‘Object of the Month’ provides an opportunity to explore interesting and unusual objects from our stores.

To celebrate harvest time our ‘Object of the Month’ for September is the nest of a Harvest Mouse, Micromys minutus, made of woven grass. It was found in a clump of Knotgrass at Sweetings Meadow nature reserve, near Thaxted in 1999. The Harvest Mouse is Britain’s smallest rodent. Weighing only 4 to 6 grams it is light enough to climb grass stems and reeds, using its paws and long prehensile tail to grip the stalks.

This is our only mouse able to build nests by weaving living grass leaves together. In summer and autumn, the mice live above ground in camouflaged nests. Breeding nests are spherical and up to 10cm diameter in size to accommodate litters of two to eight young. Single mice build smaller, less robust nests up to 5cm in size. A Harvest Mouse survey in Essex found nests in the grass of roadside verges that bordered arable fields and in reedbeds, ditches, field edges and hedgerows. The nests may be sited up to a metre above ground in dense vegetation, or in the base of a tussock of grass.

Visit the Museum in September to see the Harvest Mouse nest on display, together with a photograph of another mouse with its nest in a barn taken by a local wildlife photographer. You can also find some tiny Harvest Mice on the Natural History gallery.

Chosen by Sarah Kenyon, one of the Natural Sciences Officers at the Museum.

Harvest mouse nest SAFWM : 2001.180

Saffron Walden Museum ©

Object of the Month – June 2022

June’s object of the month celebrates the Lost Language of Nature project, with repair work to this hen harrier. With Lost Language of Nature, we want to hear your stories about wildlife and nature in your life, or rhymes, songs and sayings for all kinds of animals that you might have heard from parents or grandparents. For example, different old names across the country for hen harriers include Blue sleeves, Vuzz kitt, Grey gled, Furze kite and Goss harrier; or Ringtail for females, like this fragile mounted skin. Head to our website for more information https://www.swmuseumlearning.com/the-lost-language-project

This bird came to the Museum in the 1800s, and was taken from the area around Saffron Walden. Today, hen harriers only live in the north of England, north Wales, in Scotland and on Scottish islands, including Arran and Orkney.

Hen harrier on temporary base during conservation work.

Hen harriers today

Hen harriers are one of the UK’s most endangered birds of prey, with only an estimated 545 breeding pairs left in the country. They are on the RSPB’s Red List of endangered species in Britain, but listed as ‘Least Concern’ globally by the International Union for Conservation of Nature.

Work carried out by the RSPB suggests that over 2,500 pairs could survive in the UK. They live in open areas with low vegetation, like heather moors.

Between 2014 and 2019, the RSPB ran the LIFE project to learn more about hen harriers in Britain, their movements throughout the year and to understand why their numbers are so low. They tagged over 100 birds that they tracked using satellites, and found that some fly 1000 miles to spend the winter in Spain and Portugal. Not all birds do this though – the brother of one of these wandering birds always stayed within 50 miles of where he hatched.

In the UK, hen harriers are protected under Schedule 1 of the Wildlife and Countryside Act, meaning it is illegal to kill, injure or capture the birds, their eggs or nests, or even disturb the birds and their young while they are nesting. Despite this, the study showed that the numbers of breeding hen harriers fell by 24% (about one-quarter) between 2004 and 2016. In particular, the project monitored seven Special Protected Areas in parts of the country where land is managed for driven grouse shooting. In these seven areas, hen harrier numbers fell by over 80%, which suggests that there is deliberate human action to reduce their numbers in these areas.

References

https://www.rspb.org.uk/birds-and-wildlife/wildlife-guides/bird-a-z/hen-harrier/

https://www.rspb.org.uk/our-work/conservation/projects/hen-harrier-life/about-the-project/

https://community.rspb.org.uk/ourwork/skydancer/b/skydancer

https://community.rspb.org.uk/ourwork/skydancer/b/skydancer/posts/hen-harrier-apollo-bomber-migrate-1000-miles-to-spain

https://www.rspb.org.uk/our-work/conservation/projects/hen-harrier-life/best-places-to-see-hen-harriersnew-page/

Identification – Sea urchin fossil

Did you know we identify items for free? Whether it’s a rock from a field or a mystery something from the back of the shed, just bring it in to the Museum and we’ll take care of the rest! (If it’s too big or heavy, just send us an email with a photo).

This piece of flint with a strange marking on it was found in Wethersfield, near Braintree.

The flint nodule has preserved the impression of part of a sea urchin, or echinoid (pronounced ek-in-oid).

The shape you see is the external mould of a single plate of the echinoid’s ‘test’, or shell. When a sea urchin dies or is eaten, the test will often break apart into the individual plates.
Flint is formed from a silica-rich goo which hardens over time, and must have formed on top of this echinoid plate and taken its shape. The plates are made from calcium carbonate and this one will have dissolved away over time, leaving the impression behind.

The shape of the plate suggests it belongs to a species in the genus Cidaris. Saffron Walden Museum has a similar echinoid, Stereocidaris sceptrifera, fossilised in chalk, on display as no. 23 in the How Did They Live display in the geology gallery (below, top). In life, the club-like spines would have been attached to the plates. One of the Museum’s volunteers took this photo of a similar echinoid found at a chalk pit in Grays, Essex (below, bottom).

Fossil in chalk of the extinct sea urchin Stereocidaris sceptrifera, on display in the Museum’s geology gallery. SAFWM : 2020.42.23

The plate in the flint nodule (and the plates in the photos) is an interambulacral plate, which make up most the test of a sea urchin. They fill the space between the ambulacral zones, which are the areas where the urchin’s tube feet pass through the test. Tube feet are used for movement and to exchange oxygen and carbon dioxide with the water for respiration. Sea urchins have 5 ambulacra arranged in a star shape, showing that they are related to starfish.

The Natural History Museum has a good page showing the structure of a sea urchin test: https://www.nhm.ac.uk/our-science/data/echinoid-directory/morphology/regulars/intro.html

The British Geological Survey has an interesting page with good photos of similar fossil echinoids – look out for Temnocidaris (Stereocidaris) sceptrifera about halfway down, and Heterocidaris wickense at the bottom: https://www.bgs.ac.uk/discovering-geology/fossils-and-geological-time/echinoids/

Another link to the NHM with photos of Stereocidaris fossils: https://www.nhm.ac.uk/our-science/data/echinoid-directory/taxa/taxon.jsp?id=1115

Object of the Month – February 2022

February’s Objects of the Month are minerals with connections to love and relationships, in honour of St Valentine’s Day on 14 February.

4 mineral specimens on a white background. Lines of shade cross the image.

Amethyst geode (top left), sapphire (bottom left), ruby crystals in sheet of mica (middle), lapis lazuli (right).

The deep red colour of high-quality rubies means it is associated with love and passion in modern societies. Throughout history it has been popular in Burma (Myanmar), Hindu culture and China as a protective gem in battle or to secure good fortune when put beneath a building’s foundations. In the UK, it is the traditional gift for a 40^th wedding anniversary.

Sapphires are popular for engagement rings, as used for Lady Diana’s engagement ring from Prince Charles. Sapphire is the traditional gift in the UK for a 45^th wedding anniversary and can symbolise truth and faithfulness. Ruby and sapphire are actually the same mineral (corundum), with different colours depending on small amounts of other metal atoms included in the crystal. Chromium makes the ruby red, while blue sapphires are coloured by iron and titanium.

Object of the Month – October

Dark stone with faint tracing of a fossil flower in two petal shapes

October’s Objects of the Month are pieces of fossilised plants.

Fossils can form in different ways depending on where they form and the type of plant or animal. Most fossils come from the hard parts of animals such as bones, teeth or shells. For plants, wood is the most common material to fossilise because it is quite hard, and takes longer to rot away than other parts.
Soft leaves and flowers need to be buried quickly in deep sediment like mud or volcanic ash where the low oxygen levels mean they won’t rot. Once underground, plant material can fossilise in different ways.

Compression

This flower is probably preserved by compression, like pressing and drying it in fine mud over millions of years. Heat and pressure deep underground turned the mud to stone and forced moisture and gases from the leaf at the same time.

The main ingredient in living plants is carbon, so a thin, black, carbon-rich film is all that’s left. In most fossils, new minerals replace the original material. But because this is a compression fossil, the carbon-rich film is the exact same carbon that was in the plant millions of years ago. Soft-bodied animals like squid can also be preserved like this.

Impression

Dark stone showing inpression of a fern leaf, with fronds alternating in an exaggerated sawtooth pattern

This fern leaf, or frond, is preserved as an impression. When something soft is preserved by compression, the shape of it is also preserved as an impression, like pressing a leaf into soft mud or clay and then removing it.

This fossil is one part of a small rock nodule which was split in two to show the leaf – this part shows the impression of the frond. Because compression and impression fossils usually form together, the word ‘adpression’ describes both at the same time.

Petrification

Wedge of dark fossil wood, narrow at left. Lines of pale grey run top-bottom showing growth rings.

Fossilised wood is often called ‘petrified’ wood, meaning wood ‘turned to stone’. It happens when the materials (cellulose and lignin) that make up the solid part of wood are replaced by minerals, turning it to stone.

Minerals dissolved in groundwater seeping through the sediment settle as solids in the microscopic cell walls of the wood as the cellulose and lignin slowly rot. This can create a perfect stone copy of the original structure of the wood.

See these objects up close in Curiosity Corner throughout October.

Image credit: Female Southern Hawker – Tom Wiersma, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons. Accessed 25.5.2023.

Image credit:
Female Southern Hawker – Tom Wiersma, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons. Accessed 25.5.2023.