Give examples of Economically Important Insects
Answers
Answer:
Insects have tremendous economic importance. Some insects produce useful substances, such as honey, wax, lacquer, and silk. Honeybees have been raised by humans for thousands of years for honey. The silkworm greatly affected human history.
Answer:
. Beneficial Insects:
Insects which produce honey, wax, lac, dyes and silk are commercially beneficial. Some insects are very helpful in destroying injurious insects.
1. Commercial Products:
Apis, the honeybees produce millions of tons of honey every year, it also gives bees wax from its combs.
Benefits of bees are cosmopolitan, not only in producing honey and wax, but also in bringing about cross-pollination of many fruits and flowers without which these plants could not exist. Tachardia, the lac insect secretes commercial lac produced from integumentary glands as a protective covering by females, shellac is made from lac in India.
Dactylopius, the cochineal insect of Mexico is found on cacti, dried bodies of females of this scale insect are used for making cochineal dyes. Bombyx and Eupterote are silk moths, they are reared in India, China, Japan and Europe, their larvae called silk worms spin cocoon of raw silk, the silk fibre is reeled off and used for making silk.
In Asiatic countries over 25 million kilograms of silk are produced annually. Dried elytra of two beetles, Lytta and Mylabris are used for making cantharidin, a powerful aphrodisiac.
The larvae of two flies, Lucilla and Phormia are used in healing such wounds of bones which do not respond to medicines, the larvae are put in wounds of bones and bone marrow, they clear away suppurating and dead tissues, prevent bacterial growth and excrete allantoin which heals the wounds.
2. Useful Predaceous Insects:
Some insects are predaceous, they feed upon and destroy a large number of injurious insects. Stagomantis, a mantis is voracious, it feeds on flies, grasshoppers and caterpillars, some of which are injurious to crops. The larvae and adults of Chilomenes, a lady-bird beetle, feed on aphids which infect cotton plants.
Novius, a lady-bird bettle, destroys scale worms which are pests of orange and lemon trees. Epicauta is a blister beetle, it deposits eggs where locusts occur, the larvae on hatching enter egg capsules of locusts and eat up masses of eggs. Calasoma, a ground beetle preys upon many kinds of lepidopterous larvae which destroy cereals and cotton.
3. Beneficial Parasitic Insects:
Some insects parasitise injurious insects, they usually lay eggs in the bodies of larvae and adults of harmful insects; the young on hatching from eggs finally kill their hosts. The larvae of Tachina and related flies are parasites of injurious lepidopterous larvae, such as army-worms which are injurious to cereals.
Larvae of hymenopteran flies and carnivorous wasps devour aphids in large numbers. Chalcids and ichneumon flies are parasitic, laying eggs in cocoon and larvae of phytophagous Lepidoptera. Apanteles, a hymenopteran fly lays eggs in army-worms and boll worms, the parasitic larvae gnaw their way through the skin of the host.
4. Scavengers:
Some insects are scavengers, they eat up dead animal and vegetable matter, thus, they prevent decay. Some ants and larvae of some flies can devour entire animal carcasses.
Injurious Insects:
Compared with beneficial insects the number of injurious insects is very large.
1. Disease Transmitting Insects:
Many types of mosquitoes, flies, fleas, lice and bugs transmit diseases to man and domestic animals, they have been described earlier in insects and diseases.
2. Household Insects:
Human food is spoiled by cockroaches, ants, flies and weevils. Tinea, Teniola and Trichophaga are clothes moths, they lay eggs on warm clothes, the larvae on hatching eat and destroy clothes, they also feed on furs, carpets and dry fruits. Anthrenus is a carpet beetle, it is a scavenger eating decaying animal matter, but its larvae destroy carpets and preserved biological specimens.
Tenebrio is the mealworm beetle, its larvae are mealworms, they eat meal, flour and stored grains, such as rice. Lepisma, the silver fish and Liposcelis, the book louse live in and destroy books and old manuscripts. Termites, the white ants cause untold destruction of books, carpets, furniture and wood-work of buildings.