A number of insects and other ‘friends’ prey on various forms of insect, animal and bird life which are harmful to garden crops. It should be emphasised, however, that such indirect means of controlling insect and other pests are rarely sufficient to keep downetc. so that they are no longer a nuisance or often a real menace to the garden. Hand-picking and preventive spraying or dusting with insecticides are additional and essential weapons of defence and should always be used where necessary. Centipedes are excellent friends to the gardener. They are generally light yellowish-brown with longer legs than millepedes and do not curl themselves up when disturbed, being active, quick-moving creatures. Centipedes prey on woodlice and small slugs. .
Lacewing Flies are greenish-coloured insects allied to dragonflies. They prey on aphids (green and black fly). Ladybirds alsoon aphids, but the young or ‘niggers’ as some people call them, are often overlooked. They are a little longer than a Ladybird and are black with yellow spots.
Ground and Rove beetles consume caterpillars, slugs and snails. Frogs, toads and hedgehogs devour slugs, beetles and the larvae or grubs of various insects. The ichneumon fly is among the most helpful of all insects. The female lays her eggs in the caterpillars of certain butterflies and moths, notably the familiar cabbage white butterfly. When the grubs have devoured the caterpillars, they spin themselves yellow silk cocoons alongside. Never destroy these cocoons.
Wasps destroy aphids early in the season but from late summer onwards they are serious pests of plums and other top fruits. See WASP. Birds can do considerable harm to many, shrubs, fruits and vegetables, and deterrents are discussed under BIRDS. It is, however, only fair to add that they do eat many harmful insect and other pests. For example, sparrows eat slugs, chaffinches consume caterpillars, robins devour various insects, slugs and wireworms, thrushes destroy snails etc. Earthworms help to aerate, drain and lighten soils by their constant movement. They also reduce organic matter into .