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Save our Butterflies: Biology and threats (1 of 2)

This is a Guest blog by DIY Garden.  Illustrations by Lizzie Harper.

Butterflies and moths have been around for millions of years. They used to be a common sight in gardens and countryside, but numbers have declined since the 1940s along with our other native wildlife species such as bees and hedgehogs.

Meadow land landscape with butterflies natural history illustration by Lizzie Harper

It will come as no surprise to hear this loss is due to destruction of natural habitats such as wildflower meadows, peat-bogs and ancient woodlands.  Intensive farming practices, roads and housing developments have stripped away the majority of their nesting and foods sites.  Climate change is partly responsible for butterfly decline too, producing wetter weather that alters the distribution of certain species.  The relentless march forward of ‘progress’ damages our 56 species of butterfly and 2,500 species of moths who are sensitive to change – but your garden can help them find food and shelter.

The Decline Of Butterflies

The State of the UK’s Butterflies Report shows ‘serious, long term and ongoing decline of UK butterflies’. It highlights how 76% of our butterfly species have declined over the past forty years, with species such as the High Brown Fritillary Argynnis adippe at risk of extinction.  The once common Small Tortoiseshell Aglais urticae has become an increasingly rare sight.

Small tortoiseshell butterfly Aglais urticae natural history illustration by Lizzie Harper
Small tortoiseshell butterfly Aglais urticae

The new State of Britain’s Larger Moths 2013 report mirrored this decline, which is hardly surprising since many moths are daytime creatures, and others are could be described as “night butterflies”.  Records show moths have declined 28% over the same period.

Why should we care about  butterflies?  Because it’s bad news for the food chain.  Animals rely on butterflies for food, including us.  Butterflies and moths are pollinators and without them our crops are in trouble.  The decline is not only of concern to butterflies, its evidence of a problem in our environment.  The face of our environment is changing.  It’s turning into an urbanised monoculture reliant on pesticides, intensive farming and building to house and feed our ever increasing population.  This comes at the cost of our wild creatures.  Some butterflies have declined so severely they’re protected under law – the Large Blue Phengaris arion, Large Copper Lycaena dispar and Swallowtail Papilio machaon being just a few at  risk of extinction.

Life Cycle of a Butterfly

It’s worth remembering that butterflies have four stages of life, so it’s no wonder environmental changes wreak havoc on their life-cycles. We all learn about the caterpillar to butterfly in primary school, but it’s easy to forget that wriggling grub emerging from a tiny egg to eat your hard grown vegetables will turn into a beautiful pollinating insect. Talk about ugly duckling syndrome!

Small tortoiseshell butterfly Aglais urticae natural history illustration by Lizzie Harper
Small tortoiseshell butterfly Aglais urticae life cycle

Of course, they will be a chrysalis for a time too.  Butterflies don’t live that long, the lifespan depending on their species and the weather.  Larger butterflies like the Peacock Aglais io can live a season with hibernation, but other smaller ones only manage a few weeks to a few months.

Peacock butterfly Aglais io natural history illustration by Lizzie Harper
Peacock butterfly Aglais io
The Anatomy of a Butterfly

A butterfly or moths wings are the most dramatic part of their anatomy, but there are other parts too (for more on insect anatomy, check out Lizzie’s blog).

They have six jointed legs beneath a head, a thorax which is the chest, and an abdomen – the tail.  A butterfly’s head has large compound eyes that allow it to check all around for predators.

It has two antennae.  Antennae assess the surrounding environment and report back on chemical activity – a bit like a snake’s tongue. They’re used to detect nectar producing plants and to track the pheromones of a mate.  Near the antennae is a special organ used for flight orientation and balance. It’s called Johnston’s organ.  Butterflies with a damaged Johnston’s organ may fly in circles and be unable to manage a straight line.

butterfly
Small copper butterfly Lycaena phlaeas with striped antennae

Butterfly wings are made from scales.  Unlike fish scales, they are made from thin material called chitin which is stretched over veins. There are four wings. The wings closest to the head are usually triangular in form, and the lower pair of wings is fan shaped. Wings provide insulation, allowing the butterfly to heat up, and are often brightly coloured to scare away predators.  Since a butterfly can’t live without warmth, the wings are a very important method of retaining and building up body heat. Wings don’t regenerate, which is why butterflies seek shelter in winds and rain.

Where do Butterflies live?

Butterfly habitat depends on the species and the point of the butterfly’s life-cycle. Species prefer different locations for shelter and egg laying, which is one of the reasons why they are declining.  Certain habitats like wildflower meadows are hard to come by – we’ve lost 97% of wildflower meadows over the past few decades.  Small Tortoiseshell butterflies lay their eggs on nettles.  Large Whites Pieris brassicae prefer your cabbages, and Brimstone butterflies Gonepteryx rhamni lay their eggs on buckthorn.

Natural history sciart entomological illustratraion of the Brimstone butterfly
Brimstone butterfly Gonepteryx rhamni

A caterpillar and chrysalis won’t go far from the food source, but an adult butterfly will spend its life on the wing searching for nectar and egg laying sites.  At night they creep into small crevices in hedgerows and masonry, or anywhere that affords them protection.

Moths do the same –there are many species of daytime moth flitting around with the butterflies.

Honeysuckle Lonicera periclymenum and elephant hawkmoth Deilephila elpenor natural history illustration by Lizzie Harper
Honeysuckle plant Elephant hawkmoth Deilephila elpenor

A butterfly house provides welcome shelter.  Place your hotel in a south facing sunny location because butterflies like warmth – their wings are adapted to soak up as much heat as possible. Ensure it remains dry inside by attaching a porch.  Fix it to a fence post or brick wall to avoid a tunnel of freezing wind.  A butterfly house stood on away from a wall or on a chain is little use.  Peacock butterflies and Tortoiseshells may hibernate in your butterfly house, so don’t take the winter months as an opportunity to clean it out.  (Click on the link for guidance on how to build a butterfly house.)

What do Butterflies eat?

Butterflies survive on nectar.  They taste it through sensors on their feet, and drink it from the flower centre using a proboscis – a long, narrow tube just like a straw. If you stand quietly to watch a butterfly at a flower you will see this fascinating body part in action.

Other sources of food depend entirely on the species but fruit, tree sap and the salt found in our sweat are attractive to some.

Caterpillars eat plants, and plenty of them, each specific to their species.  So much energy is needed to transform into a butterfly that caterpillars are mini eating machines.  Peacock caterpillars eat and live on nettles.  Comma Polygonia c-album and Red Admiral Vanessa atalanta caterpillars also love nettles.  The Elephant Hawkmoth Deilephila elpenor caterpillar dines on willowherb and fuchsia, and the Holly Blue Celastrina argiolus is specific to, you’ve guessed it, holly.

American cabbage looper Trichoplusia ni caterpillar natural history illustration by Lizzie Harper
American cabbage looper Trichoplusia ni caterpillar

Other caterpillars love trees such as alder buckthorn, some like wild roses or lavender.  In fact most native flowers and weeds are utilised by our caterpillars.  In case you were wondering, only two out of the 2500 species of moth will eat your clothes.   They only enter the house because they are attracted to light, and not because they want to dine on your expensive winter wool coat!

Do Butterflies have any predators?

Unfortunately for butterflies they have a range of predators at their caterpillar, pupa and adult stage. Birds, spiders, frogs, toads, hedgehogs, bats, cats, dogs, wasps all eat caterpillars, butterflies and moths.

Butterflies are especially vulnerable when they emerge from the chrysalis as they need to pump liquid into their wings and wait patiently for them to harden before flying away.

To protect themselves an array of defences have developed.  Caterpillars blend into the foliage, have bright colours to indicate danger, or may have spines.

Butterflies often have bright markings that mimic something dangerous – for example the Peacock butterfly has two large spots that resemble eyes on his wings to scare predators, but at rest the wings are closed up to reveal a dull, camouflaged grey. When folded a butterfly is so thin it’s difficult to spot from above.  Some caterpillars and butterflies release a chemical scent to deter predators and other have foul smelling parts such as the Swallowtail.

Swallowtail butterfly Papilio machaon natural history illustration by Lizzie Harper
Swallowtail butterfly Papilio machaon
Do Butterflies hibernate?

Some of the larger UK butterflies hibernate as eggs, caterpillars, a chrysalis, or as fully fledged adults.

Some annual visitors such as the Painted Lady Vanessa carduii can’t stand winter temperatures, and fly to back to warmer African climates.  Most Painted Ladies returning to Africa in autumn are fresh, following in their parents’ footsteps with no directions or guidance. The fact they can do this at an altitude of 500 metres makes the Painted Lady an astonishing creature.

life cycle, cycles, adult, larva, natural history illustration, natural science illustration,
Painted lady Vanessa carduii life cycle

Those hibernating do so in the coldest winter months as there are no food sources available. Brimstone, Small Tortoiseshell, Red admiral and Peacocks will all hibernate.  Hibernation could occur in your butterfly hotel, in dried-out grass stalks, in brickwork, or in your house.

Don’t disturb a hibernating butterfly, they do not harm, and releasing one that’s woken in the central heating means death if it’s cold outside. Instead, put it in a shoe-box with a thin cut on one side.  Then place it in a cold, dark place like your garage or shed to continue hibernating.  The slot is vital – don’t forget to cut the box so a waking butterfly can escape on its own. If it’s warm and sunny outside put the box into a hot spot, and the butterfly will fly away – if it made it through hibernation safely.  Many don’t make it, either running out of stored energy or falling ill to fungal infections in damp hibernation spots.

Conclusion

Butterflies are amazing, and threatened insects.  We must all do what we can to help.

Join a charity such as Butterfly Conservation, and learn how to make your garden into a haven for these animals in the next blog by DIY Garden: Save our Butterflies: Gardening for Butterflies

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Lizzie Harper