According to A D. Imms there 29 insect orders. These are as following

The Apterygota

Protura

Collembola Springtails

Thysanura Silverfish

Diplura Two Pronged Bristle-tails

The Exopterygota

Ephemeroptera Mayflies

Odonata Dragonflies

Plecoptera Stoneflies

Grylloblatodea

Orthoptera

Phasmida Stick-Insects

Dermaptera Earwigs

Embioptera Web Spinners

Dictyoptera Cockroaches and Mantids

Isoptera Termites

Zoraptera

Psocoptera Bark and Book Lice

Mallophaga Biting Lice

Siphunculata Sucking Lice

Hemiptera True Bugs

Thysanoptera

The Endopterygota

Neuropter Lacewings

Coleoptera Beetles

Strepsiptera Stylops

Mecoptera Scorpionflies

Siphonaptera Fleas

Diptera True Flies

Lepidoptera Butterflies and Moths

Trichoptera Caddis Flies

Hymenoptera Ants Bees and Wasps

Dear Dr. Upadhyay,

Thanks for your very prompt reply. I was in your department few years ago to attend a symposium organized by Prof. Rajendra Singh. However, can you please mention the year of last edition of the said book (A D. Imms) from where you referred.

With extension of Imms ...Mantophasmoiteda is newly member have been incorporated.  

In recent classification, there are 30 orders of Insects, which are as follow:

Protura, Diplura, Collembola, Archeognatha (=Microcoryphia), Thysanura, Odonata, Ephemeroptera, Grylloblattodea, Plecoptera, Embioptera, Phasmida, Orthoptera, Blattodea, Mantodea, Dermaptera, Isoptera, Zoraptera, Psocoptera, Phthiraptera, Thysanoptera, Hemiptera, Strepsiptera, Neuroptera, Mecoptera, Coleoptera, Diptera, Siphonaptera, Trichoptera, Hymenoptera, Lepidoptera

Dear Prof. Singh,

Thanks for your sharing. How are you?

I got (personal communication) the following comments on this issue from an expert. These are:

" It is indeed challenging to select a consensus classification of insects at the ordinal level, since there are numerous competing ideas and ongoing changes as research continues on the relationships among the orders..... Such changes as including Isoptera within Blattodea, Phthiraptera within Psocodea, and "Homoptera" within Hemiptera seem to be becoming better and better established as time goes on..."

Margaret Thayer

Margaret K. Thayer, Ph.D.

Curator Emeritus, Field Museum of Natural History

Lecturer, Committee on Evolutionary Biology, University of Chicago

Fieldiana Life and Earth Sciences - Associate Editor (Zoology)

1400 South Lake Shore Drive

Chicago IL 60605-2496, USA

PHONE: +1-312-665-7741 (direct) FAX: +1-312-665-7754

FMNH personal web page Austral Staphylinidae & Staphyliniformia databases

FMNH Insects collection database

Dr. Thayer is right. Sometime the understanding of rank of taxonomic category is difficult. Recently, Phylum Arthropoda is divided into 5 subphyla, all arthropods having six legs are grouped under subphylum Hexapoda. The Hexapoda is divided into two classes : Entognatha (retracted within the head) and Insecta (Ectognatha, no taxonomic rank, head not retracted). The class Entognatha is divided into 3 orders Protura, Collembola, and Diplura. Class Insecta is divided into three subclasses: Monocondylia, Apterygota and Pterygota. Monocondylia consists of only one order Archaeognatha (=Microcoryphia). Apterygota includes order Thysanura. Isoptera as suborder of Blattodea.

How many insect pests species do we know?

Sharp decline of insect populations in many insect orders due to unregulated use of insecticides/ other pesticides, chemicals pollution. This is going to effect all food web/ chains on the planet.

Dear Dr. Ahmad,

Thanks for your comment. Yes, this is true; but we do not have precise statistics on this. Most of us are interested on big animals, i.e. charismatic group and the insects are really neglected group for conservation practitioners. This attitude should be changed in order to conserve the diversity of lives on this planet.

Dear Dr. Chandra Das,

Thanks, as I am aware there are only, only max 10000 insect species as pests, including all types of pests and this is from more than about 3 million insect species .....this is important to know that now for many years since 20 century there are many extinctions and so surely number of species and even insect speciation is decreasing.

It is hard to say these number of insect orders but i have got 34 orders. The number increased from 29 to 34 or more because of split of few orders like Orthoptera in to three and another new insect obtained from South Africa.

Here are the list of the 34 orders'. I have collected from different sources.

Protura ………….. Proturan

2. Diplura …………. Dipluran

3. Collembola …….. Springtail

4. Microcoryphia …. Jumping Bristletails

5. Thysanura ……… Silverfish

6. Ephemeroptera … Mayflies

7. Odonata … Dragonflies and Damselflies

8. Blattodea ……….. Cockroaches

9. **Mantodea ………. Mantids

10. *Isoptera ………… Termites

11. Zoraptera ………. Zorapterans

12. Grylloblattodea … Ice Insects

13. **Dermaptera …….. Earwigs

14. Plecoptera ……… Stoneflies

15. *Orthoptera … Grasshoppers and Crickets

16. **Phasmatodea …… Walkingsticks

17. Embioptera ……. Webspinners

18. Psocoptera ……… Book Lice

19. Mallophaga …….. Chewing Lice

20. Anoplura ……….. Sucking Lice

21. *Hemiptera ……… True Bugs

22. *Homoptera …….. Leafhoppers, Cicadas, etc

23. *Thysanoptera ….. Thrips

24. Megaloptera …… Alderflies and Dobsonflies

25. Raphidioptera …. Snakeflies

26. **Neuroptera …….. Lacewings

27. *Coleoptera ……... Beetles

28. Strepsiptera ……. Twisted-Wings

29. Mecoptera ……… Scorpionflies

30. Siphonaptera …… Fleas

31. Tricoptera ……… Caddisflies

32. *Diptera …………. Flies

33. *Lepidoptera ……. Butterflies and Moths

34. Hymenoptera …… Bees, Wasps, and Ants

Dear Dr. Dejen Asmare,

Thanks for your feedback. However, Protura, Diplura & Collembola are no longer insects orders. They are considered as non-insect hexapod by an authority (P.J. Gullan and P.S. Cranston (2014): The Insects: An Outline of Entomology, 5th Edition.

Thanks Dr. Chandra Das,

Is this accepted globally now that these three orders called in the past "Ametabola" are no longer insect orders?

Would you refer on recent books? The book you mentioned, i have it but it old.

https://www.insectidentification.org/orders_insect.asp