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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Content last updated: 17/10/2005

About our writer

Patricia Ash is an associate lecturer in science and biology with the Open University and also works as a consultant in the fields of biology and the environment. Her research is a study of the ecology and diet preferences of the speckled bush cricket in two locations: the coast and Oxfordshire.

Previously she worked for the Medical Research Council as a member of the Scientific Secretariat for the Committee for Protection against Ionizing Radiation. Her role was to study the medical effects of ingested radionuclides, such as plutonium-239 and strontium-90 and also to monitor reports on radioactive discharges from nuclear power stations.

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