Insects have an important role as part of the living planet, and they make up four-fifths of all animal species. But what difference do they make to our lives?

Insects as a problem

【小题1】We plant crops which some insect species love, and they thrive on them. That’s when we start to call them pests.

Humans have caused some insect species to be moved from one part of the world to another—deliberately or by accident. If the introduced insect species has no natural enemies in their new home, they can become a real problem. A recent UK example is the Harlequin ladybird, which has found its way to Britain and eats other ladybirds.

Some insects can sting, bite, or transmit disease to humans.【小题2】Mosquitoes, for example, gain nourishment by sucking blood, and in the process they can transmit diseases, such as malaria.

So, when it comes to insects, its important to understand the consequences of human actions.

Insects as an opportunity

Insects are very important as pollinators(传粉者). Bees are perhaps the best example of this. 【小题3】Pollination is needed before many crops and fruits that we eat can be formed.

Insects are also useful as models in scientific research. The Fruit Fly is a good example. It breeds rapidly, and can produce very many generations per year in the laboratory, so it is ideal for the study of evolution.【小题4】

Insects can be useful to the gardener too—ladybirds, for example, are the gardeners’ friend because they eat aphids. Hoverflies and wasps also hunt and kill other insects for food in the garden. These species are called predators(捕食者).

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