Applied entomology has as its aim the manipulation of insects (both harmful and beneficial) to man’s advantage. Successful manipulation of any organism depends on adequate biological understanding. Since time immemorial mankind has had to contend with insect pests which attack his cultivated plants, his domestic animals and his person. However, insects have also long provided man with valued products, in particular,honey, wax, silk, lac etc., so their actions are not entirely harmful. In addition, in more recent years, the beneficial roles of insects in facilitating pollination of many cultivated plants and as natural enemies of pest species have been recognized. Some knowledge of insects, both harmful and beneficial, is therefore essential for anyone engaged in agriculture or horticulture.