Economic classification of insects

• Insects can be classified as follows based on their economic importance.

This classification us according to TVR Ayyar. 

Insects of not economic importance

• There are many insects found in forests, and agricultural lands which neither cause harm nor benefit us.

• They are classified under this category. 

• Human beings came into existence 1 million years ago. 

• Insects which constitute 70-90% of all animals present in this world came into existence 250- 500 million years ago.

Insects of economic importance 

A. Harmful insects 

a) Pest of crop (Pests of cultivated plants)  

• Each cultivated plant harbors many insects pests which feed on them reduce the yield of the crop. 

• Field crops and horticultural crops are attacked by many insect species. (eg) cotton bollworm, Rice stem bores.

b) Pests of Storage produce

• Insects feed on stored products and cause economic loss. (eg) Rice weevil, Pulse beetle.

c) Pest of farm animals (Pest attacking cattle and domestic animals)

• Cattle are affected by pests like Horse fly, Fleshfly, Flese and Lice. They suck blood and sometimes eat the flesh.

d) Pest of Public health

• Disease carrying insects are mosquitoes, houseflies, bed bugs, fleas etc.

• Disease causing Mosquito- Malaria, Filariasis ,dengue fever. Housefly- Typhoid, Cholera, Leprosy, Anthrax

  e) Pest of House hold 

• Pests which cause damage to belongings of human being like furniture, wool, paper etc. Eg. Cockroaches, furniture beetle, sliver fish etc.

• Pests which cause painful bite, inject venoms. Eg. Wasps, bees sting us. Hairy caterpillar nettling hairs are poisonous. Mosquitoes, bugs bite, piece and suck blood from us.

B. Beneficial insects 

a) Productive insects 

i) Silk worm 

• The silk worm filament secreted from the salivary gland of the larva helps us in producing silk.

ii) Honey bee 

• Provides us with honey and many other by products like bees wax and royal jelly.

iii) Lac insects 

• The secretion from the body of these scale insects is called lac. Useful in making vanishes and polishes.

iv) Miscellaneous (Insects useful as drugs, food, ornaments etc,) 

 (a) As medicine eg. Sting of honey bees- remedy for rhenmatism and arthritis 

• canthoridin - extracted from blister beetle –useful as hair tonic.

(b) As food - for animals and human being. 

• For animals- aquatic insects used as fish food.

• Grass hoppers, termites, pupae of moths.

• They have been used as food by human beings in different parts of the world.

(c) Ornaments, entertainers 

• Artists and designers copy colour of butterflies.

• Beetles worm as necklace.

• Insect collection is a hobby

(d) Scientific research 

• Drosophila and mosquitoes are useful in genetic and toxicological studies respectively.

(II) Helpful insects 

(i) Parasitoids 

• These are small insects which feed and live on harmful insects by completing their life cycle in a host and kill the host insect.

• Eg. Egg, larval and pupal parasitoids

(ii) Predators

• These are large insects which capture and devour harmful insects.

• Eg. Coccinellids, preying mantids.

(iii)Pollinators 

• Many cross pollinated plants depend on insects for pollination and fruit set.

• Eg. Honey bees, aid in pollination of sunflower crop.

(iv)Weed killers 

• Insects which feed on weeds kill them thereby killers.

• Eg. Parthenium beetle eats on parthenium. Cochineal insect feeds in Opuntia dillenii.

(v) Soil builders 

• Soil insects such as ants, beetles, larval of cutworms, crickets, collembola, make tunnels in soil and facilitate aeration in soil. They become good manure after death and enrish soil.

(vi) Scavengers

• Insects which feed on dead and decaying matter are called scavengers. They important for maintaining hygine in the surroundings.

• Eg. Carrion beetles, Rove beetles feed on dead animals and plants.