Mostly insects are thought to be pestiferous creatures that should be destroyed at all cost. But there are many beneficial acts performed by insects that are indispensable to man.
Productive insects: Human beings are greatly indebted to certain insects, which supply them with useful products. Many commercial products produced by insects are indispensable to modern man. Honey and beewax are produced by the honey bees. Certain scale-insects also produce wax. The silkworms supply the commercial silk. Lac insects belonging to the family Coccidae secrete a wax known as shellac. The dyes tannin and cochineal are derived from the dried bodies of certain scale-insects living on cacti.
Pollinators of flowers: The greatest service rendered to man by his ‘insect friends’ is the pollination of flowers. Cross fertilization or cross pollination is very necessary for the fertility and the vigour of plants which depend upon certain insects for this purpose. In some cases special flower developments favour insect visits. Many insects and flowers are mutually dependent since many insects feed upon the nectar and pollen grains of the flowers. Among the outstanding pollinators are the bees, wasps, beetles, ants, flies etc.
Scavengers: The insects feed upon the waste materials such as the dead bodies and debris of plants and animals, thus preventing decay and obnoxious odours. The common examples of insect scavengers are the silverfish, termites, housefly, blowfly, maggots, dung beetles, carrion beetles, fleas, cockroaches and many larvae.
Insects as food: The insects provide an abundant food supply for animals like, frogs, lizards, snakes fishes, etc. Blue-birds, meadow-larks, and house sparrows depend chiefly on insects. Moles, shrews, armadillos, and ant eaters live wholly upon small insects. Man consumes many insects and their larvae, eggs, only accidently with fruits and other foods. The natives of Amazon valley eat Suab-ants. Termites form favourite food in tropics. Eggs of Coriza femorata are taken in Mexico, while larvae of Goliath beetle of Africa are a fine food morsel. The Greeks ground locusts in mortars and made flour of them. American Indians used to dry or smoke the larger caterpillars and preserve them for later use.
Insects in medicines: The cochineal insects contain carminic acid, coccerin, myrestin, fat and fatty acids and are used in the treatment of neuralgia, and whooping cough. Blowfly larvae are use in treating decay of tissues. Canthardin oil made out of blister-beetles, serve as hair restorer. The body extract of the cocoons of the silk moth, is used for checking profuse menstruation and in treating leucorrhoea and chronic diarrhea. Bee-venom has been used with some degree of success in treatment of some forms of arthritis. Bee-venom has also been used in the preparation of anti-venom to counteract snake bite. Honey is a natural antiseptic which prevents infection if applied to a wound. It is also applied to cure ulcers. The beewax is used as a base for ointments.