This classification is according to TVR Ayyar

1. Dr. Majid Jamali
IMPORTANCE OF CLASS INSECTA
Assistant Professor
School of Agricultural Sciences
Glocal University
Saharanpur
Entomology

2. Insects which constitute 70-90% of all animals
present in this world came into existence 250-
500 million years ago during Ordovician period.
On the basis of their economic importance insects
can be classified as:
1. Insects of no
economic importance
2. Insects of economic
importance

3. Most of the insects found in forests, and
agricultural lands which neither cause harm nor
benefit us.
1. INSECTS OF NO ECONOMIC IMPORTANCE

4. 2. INSECTS OF ECONOMIC IMPORTANCE
A. Injurious insects
a). Pests of cultivated crop
 Field crops and horticultural crops are attacked
by many insect species.
 These pests feed on them and reduce the
yield.
Example: Thrips, rice stem bores etc.
b). Storage pests
 Insects feed on stored products and cause
economic loss.
Example: Rice weevil, Pulse beetle.

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c). Pest attacking cattle and domestic animals
 They suck blood and sometimes eat the flash of
cattle.
Example: Horse fly, Flesh fly, Flee & Lice.
d). House hold pest
 Pests which cause damage to belongings of human
being like furniture, wool, paper etc.
Example: Cockroaches, furniture beetle, sliver fish
etc.
 Pests which cause painful bite, inject venoms.
Example: wasps, bees sting us.

6. e). Disease carrying/ causing insects
 Disease carrying insects are mosquitoes,
houseflies, bed bugs, fleas etc.
Mosquito causes- Malaria, Filariasis, Dengue fever.
Housefly causes-Typhoid, Cholera, Leprosy,
Anthrax

7. B. Beneficial insects
a) Productive insects
Silk worm: The silk worm filament secreted
from the salivary gland of the larva helps us in
producing silk.
Honey bee: Provides us with honey and many
other byproducts like bees wax and royal jelly.
Lac insects: The secretion from the body of these
scale insects is called lac. Useful in making vanishes
and polishes.

8. b). Use as medicine
Sting of honey bees- remedy for rheumatism and
arthritis.
Eanthoridin - extracted from blister beetle –useful as
hair tonic.
c). As food: Used as for animals and human being.
They have been used as food by human beings in
different parts of the world.
For animals- aquatic insects used as fish food. Grass
hoppers, termites, pupae of moths.

9. d). Ornaments, entertainers
 Artists and designers copy colour of butterflies.
 Beetles worm as necklace.
e).Scientific research
 Drosophila and mosquitoes are useful in genetic
and toxicological studies respectively.

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f). Other useful insects
Parasitoids
 Parasitoids are species whose immature develops
on or within a single insect host, ultimately killing
or fatally infecting the host.
 These may be egg, larval or pupal parasitoids.
Example. Trchogramma,Encarcia.
Predators
 These are large insects which capture and devour
harmful insects.
Example. Coccimellid beetles, Preying mantis.

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Pollinators: Many cross pollinated plants depend on
insects for pollination.
Example: Honey bees, butterfly.
Weed killers: Insects which feed on weeds, kill
them thereby killers.
Example: Mexican beetle, Cochineal insect.
Scavengers: These insects feed on dead and
decaying matter and maintaining hygiene in the
surroundings.
Example: Carrion beetles, Rove beetles.