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Friends, Foes And Aliens

Updated Wednesday 9th November 2005

Do you have an insect-friendly garden? Not all insects are pests and there are many beneficial insects that prey on invertebrate garden pests, reveals Patricia Ash.

Butterfly on flower Copyrighted image Icon Copyright: Patricia Ash

Beneficial insects also include hoverflies and bees, which are essential for pollinating food crops. We benefit too from the enjoyment of seeing beautiful insects, such as butterflies and dragonflies. In addition, insects provide important food for birds such as sparrows, robins, house martins, swifts, fly-catchers and blue tits.

Everyone can encourage beneficial insects by stocking a garden, balcony or window box with suitable plants.

Early spring is a crucial time for insects, as they emerge from winter dormancy needing to feed to replenish their energy reserves. To help these insects to survive, choose spring plants with flowers rich in nectar and pollen such as bluebells, Pulmonaria, primroses, celandines and rosemary.

Grow a selection of plants to provide flowers all year round. Plant borage, sage, thyme, marjoram and fennel, in patio pots or in your garden, and you have fresh herbs for cooking, and bees, butterflies and hoverflies have nectar and pollen from the flowers. Shrubs with attractive flowers for bees, hoverflies and butterflies include Buddleia, honeysuckle, bramble and Cotoneaster. Ivy is important as the flowers provide nectar in winter. Choose herbaceous plants such as lupins, foxgloves, lavender, teasel, sunflowers, ice plant and aquilegia.

If you have space, leave a sunny area to go wild, and let nettles grow, the food plants of caterpillars of at least five butterflies. Seeds of native wild flowers can be bought and sown in your wild corner: choose vipers bugloss, lady’s smock, daisies and clovers.

Leave some logs in a pile to provide shelter for ground beetles and devils coach horses, which prey on slugs and snails hiding under the logs. A garden pond provides a habitat for aquatic insects, including dragonfly nymphs, which develop into beautiful adult dragonflies. There is more guidance on planting a garden that attracts beneficial insects on the National Insect Week website.

Beneficial insects living in your wild area can include common green lacewings, green insects with large transparent iridescent wings. Ladybirds are well-loved brightly-coloured small beetles, most red or yellow with black spots. In summer, adult ladybirds and lacewing and ladybird larvae prey on aphids, scale insects and caterpillars. In your garden these insects will soon find and eat aphids infesting your plants.

Why is it that one day you wander into your garden and notice that your roses or bean plants are infested with huge numbers of greenfly, when just a few days ago, there were none? You have witnessed the result of a huge population explosion. The secret of aphid success is that in spring and summer, the females reproduce without males.

Female aphids give birth to tiny live females that immediately set to work sticking their long needle-like mouthparts into plant stems and leaves to suck up sugary plant sap. As aphids fly or crawl from plant to plant, and suck sap they spread virus diseases, deplete plants of nutrients and spoil and diminish crops. Aphid-infested French beans have a gnarled twisted look and garden plants are blackened by mould growing on the sticky sugars excreted by the aphids.

Pause to take a close look at an aphid colony before you decide to zap it with insecticide. You are likely to see voracious aphid predators, ladybirds and their larvae, eating the greenfly on your roses or beans.

The most common garden ladybirds are the seven-spot, two-spot and 14 spot, all aphid eaters. The seven-spot is five to eight milimetres long with three black spots on each red wing case, and one at the front spreading across both wing cases. The adults are dormant in winter, hiding in crevices in tree branches and bushes.

They become active between February and March and feed on pollen and nectar in early-flowering plants, as well as any aphids they find. Peak aphid time comes later on, and then a seven-spot eats up to 70 aphids a day over about six months.

After mating, a female seven-spot can lay 1,500 eggs, each hatching into a larva that eats about 500 aphids before it pupates and develops into an adult. Two-spot ladybirds are red with two spots, and smaller than seven-spots. 14-spots are yellow with 14 black spots.

You may find other ladybirds in your garden, especially if you have trees.An easy-to-use guide to identifying 23 species can be downloaded from the Nature Detectives website.

You can also help with a scientific investigation. UK Phenology is collecting information about the dates and places that people first see a seven-spot ladybird. This study is monitoring the effects of global warming. As the climate warms, the timing of natural, seasonal events such as the emergence of ladybirds changes. Phenology studies the timing of these events from year to year. One finding is that seven-spot ladybirds are first appearing 11-14 days earlier in comparison to 20 years ago.

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Butterfly on flower Copyrighted image Icon Copyright: Patricia Ash

Your observations may assist in monitoring the spread of the alien harlequin ladybird, imported by commercial greenhouse owners to control aphids. Some harlequin ladybirds escaped and multiplied and colonised mainland Europe. They reached southeast England in 2004. Harlequin ladybirds eat aphids - but they also eat our native ladybirds. In cold weather, they congregate in houses, and they bite and spit a bright yellow liquid, which stains clothes and soft furnishings. Log into the Harlequin Survey where there is guidance on how to recognize these aliens and send in records of sightings.

Pollinators such as hoverflies and bumblebees are of the utmost importance for food crops such as beans, courgettes and fruit. The bad news is that bumblebees have declined in recent years because of a reduction in plant diversity. They are especially vulnerable in early Spring, when queen bumblebees emerge from winter dormancy. They need nutritious nectar and pollen to sustain them in their search for a nest site, which they prepare for egg laying. By planting nectar-rich plants in your garden, patio or window box, you help the bees to survive.

A bee gathers pollen Copyrighted image Icon Copyright: Used with permission

Bumblebees have specialised mouthparts, which form a long tongue that laps up nectar from flowers. The length of the tongue varies in different species so choose a variety of plants. Give the queens another helping hand in spring by providing bumblebee nest boxes in your garden, available from a number of suppliers. It is also possible to make simple bumblebee nesting boxes. Check out the instructions for making a bumblebee or mason bee box.

Once you have made your bumblebee box, place it in a flower bed, or under a hedge so that the bees have easy access to flowers.

There are about 26 different bumblebee species in the UK; most are rare. If you are interested in identifying bumblebees there are good guides available and a simple one is available from Rothamsted experimental station. This guide helps you to identify the six most common species in the UK.

Very few of our butterflies are pests and so it is worthwhile preparing a garden that attracts these beautiful insects. Your nettle patch may feed caterpillars of red admiral, peacock, comma and small tortoiseshell butterflies. Orange tip butterflies can be seen in gardens, and their caterpillars feed on ladies smock, which is not difficult to establish in a damp lawn. You may spot common blues; their caterpillars eat clovers and related plants. Holly blues may be seen if there are holly trees and ivy in your area.

In contrast to their leaf-eating caterpillars, adult butterflies feed on nectar, by sucking it from flowers using a long tube or proboscis, which when not in use is curled up under the head. Take the time to watch butterfly behaviour and have a butterfly guide handy for identifying them. You can take your interest in butterflies further with the butterfly monitoring scheme, which collects data on sightings of butterflies and so obtains information on increases and declines in numbers of the 71 species of butterfly in the British Isles.

Insect diversity is so huge that we have only covered a minute proportion of the insects found in gardens. If you search for insects in your garden, or use some means of collecting them such as passing sweep nets through shrubs or long grass, and using a moth trap, you will find many more species. Sweep nets and moth traps can be made from items found in the home.

To identify the insects you find, use guides. For example, the Field Studies Council publishes a collection of reasonably priced guides of particular types of insects. Keep a note of the species that you find in your garden and you can build up a year-by-year record. Most important of all, enjoy the diversity of insect life in your garden!

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