Butterflies are one of the most sought after visitors to gardens. They are very valuable insects in the garden as they carry pollen whilst flitting from flower to flower in search of sugary, energy-giving nectar. Around sixty native species of butterfly are to be found in the UK.

Eggs, caterpillars, chrysalises and butterflies are very variable in terms of size and colour. Eggs are usually around 1mm tall and spherical or elongated. Like the adult, the caterpillar has six legs on the thorax but also has around eight stumpy prolegs which have tiny hooks and a pair of claspers at the rear. Chrysalises are usually dark colours for camouflage. Butterflies are the most often seen stage and are the familiar beautful colours and fascinating flight patterns.

Butterflies and moths are often confused but there are some general rules: butterfly antennae have swollen tips whereas moth antennae are toothed or hair-, comb- or feather-like; butterflies generally fly by day and moths by night; and butterflies hold their wings vertically above their body when at rest whereas resting moths fold their wings in a roof shape or flat over the body.

The intensification of agriculture has contributed significantly to the decline of butterflies. Caterpillars mostly eat wild flowers that only grow on poor soils. Farmland fertilisers make the soil too rich, reducing the number of plants for butterflies to lay eggs on and for caterpillars to eat. For species that live on grass, regular cutting and grazing destroys eggs, caterpillars and the food source. The use of weedkillers removes food plants and pesticides kill caterpillars and butterflies.

Woodlands are home to many species of butterfly but many have been cleared to make way for plantations of conifers which block light and prevent the growth of wild food plants. Woodlands were once well-managed with regular cutting which let in light and encouraged food plants to grow. These days many woodlands are dark with little vegetation.

The drainage of marshes and fens and the extraction of peat from bogs has had a dramatic effect on marsh species and insensitive road, house and industry building projects have all taken their toll.

The typical gardener is both friend and foe. Many gardens offer rich pickings in terms of nectar for butterflies. Yet, whilst many gardeners adore butterflies, they often have much less respect for caterpillars which are regarded as pests. Butterflies have also inadvertently being pushed out of gardens as gardening fashion has shifted away from the rich provisions of the cottage garden to the relative sterility of manicured lawns, ornamental plants and flowerless plants such as conifers. Other dangers come from collectors who kill specimens and people keeping these wild animals as pets.

There's lots we can do to help. Grow wildflowers and leave areas of long grass for caterpillars. Grow plenty of single flowers rather than doubles for butterflies as they usually yield more nectar. Favourites are: sweet rocket, buddleia, michaelmas daisy, red clover, birdsfoot trefoil, red valerian, field scabious, verbena, rosemary, golden rod, marjoram, ice plant (Sedum spectabile), which should be planted in groups. Provide butterfly houses for butterflies to shelter and hibernate in. Avoid using pesticides and artificial fertilisers.

Caterpillars eat vegetation specific to the species. Butterflies are far less picky, taking nectar from all sorts of flowers as well as honeydew secretions from aphids, tree sap and wet soil.

Eggs are laid on the food plant of the caterpillar which varies between species. They are laid singly, in rows, or in clusters, usually on the underside of leaves or on stems. The number of eggs laid varies from around twenty to several thousand. The caterpillars usually hatch within one to three weeks although in some species, such as the wall brown, the eggs over-winter with a hibernating caterpillar inside.

The caterpillar needs to eat enough to carry it through hibernation or the next stage of metamorphosis, that is, the change from caterpillar to butterfly via the pupal (chrysalis) stage. The caterpillar grows very quickly. The caterpillar has to moult as the skin becomes tight. Many moults will take place before the caterpillar is fully grown, which may take only a few weeks.

The final moult results in a chrysalis or pupa. The soft skin hardens. Inside, the animal undergoes the massive transformation into an adult. Most species hibernate during the pupal stage, often as fully developed adults which are ready to emerge in spring as plants begin to flower and nectar becomes available.

Emergence of the adult from the pupa only takes a few seconds or minutes. First the butterfly pumps up the tubes in its fore- and hind-wings with blood and air. This takes ten minutes or so. The following few hours are risky for the butterfly as it is easy prey while it waits for its wings to harden before they are ready for flight. The transparent wings are covered in millions of individual pigmented scales which are already arranged into the familiar patterns we see. These sometimes reflect and refract light to produce a stunning metallic sheen.

Butterflies need places to shelter from the rain and wind. Many butterflies, including Peacocks and Small Tortoiseshells need places to hibernate from autumn until spring when flowers are few. The ideal spot will be dry, insulating and without easy access for predators. Butterfly houses are ideal. Like hedgehogs and bats, they wake temporarily in warmer weather and often seek new accomodation.

Birds, bats, spiders and parasitic wasps attack butterflies at various parts of the lifecycle. There are some interesting defences. Eggs are ususally laid on the underside of leaves. Some caterpillars look like twigs, leaves or bird droppings, or they have hairs, or they release unpleasant tastes, poisons or smells as a deterrent. They are best not handled! Butterflies are often either camouflaged or have bright warning markings. The Peacock butterfly looks like its has an extra pair of eyes to scare predators away!

This is very variable across species. Some such as small tortoiseshells are common. However, five species have become extinct since the mid-1800s and others such as the heath fritillary (Mellicta athalia) are at risk.

A swallowtail caterpillar's weight increases a thousand-fold in just two weeks - faster than any other animal.

Please don't be tempted to keep caterpillars and butterflies. Many caterpillars each year die in claustrophobic jam jars stuffed with wilting leaves and butterflies lose their scales easily as they try to escape. Look on the underside of leaves for eggs, in sheds for chrysalises, near holes on vegetation for caterpillars and in the flower border or wildflower meadow for butterflies. Butterflies are fond of sugary water and yellow colours.