🗂️ Classification of Class Insecta

Classification of Class Insecta helps organize the enormous diversity of insects into manageable groups. For exam purposes, the major focus is on the broad division of Insecta into subclasses and on the distinction between exopterygote and endopterygote orders.

Classification of Class Insecta up to Orders

Insects are six-legged arthropods belonging to:

• Phylum: Arthropoda
• Class: Insecta or Hexapoda

A widely taught classification was proposed by A. D. Imms.

Characters of Class Insecta

Important general characters of insects are:

1. Body divided into three regions: head, thorax, and abdomen
2. One pair of antennae usually present
3. One pair of compound eyes usually present
4. Thorax bears three pairs of legs
5. Usually two pairs of wings are present
6. Excretion mainly through Malpighian tubules
7. Respiration by a well-developed tracheal system
8. Brain divided into protocerebrum, deutocerebrum, and tritocerebrum

Subclasses of Insecta

Class Insecta is divided into two subclasses:

1. Apterygota
2. Pterygota

Comparison of Apterygota and Pterygota

Character	Apterygota	Pterygota
Wings	Primarily wingless; evolved from wingless ancestors	Winged or secondarily wingless; evolved from winged ancestors
Metamorphosis	Absent or slight	Present
Mandibular articulation	Monocondylic	Dicondylic
Pleural sulcus	Absent	Present
Pregenital abdominal appendages	Present	Absent

Examples of secondarily wingless pterygotes include flea, head louse, and bed bug.

Orders of Subclass Apterygota

The subclass Apterygota includes four important orders:

1. Thysanura: silverfish
2. Collembola: springtails or snow fleas
3. Protura: proturans
4. Diplura: diplurans or japygids

Divisions of Subclass Pterygota

The subclass Pterygota is divided into two major groups based on wing development:

1. Exopterygota
2. Endopterygota

Comparison of Exopterygota and Endopterygota

Character	Exopterygota	Endopterygota
Wing development	External	Internal
Metamorphosis	Gradual or incomplete	Complete
Pupal stage	Absent	Present
Immature stage	Nymph or naiad	Larva
Number of orders	16	9

Thus, the commonly taught total becomes:

• 4 orders in Apterygota
• 25 orders in Pterygota
• 29 orders in Class Insecta

Exopterygota Orders

Group I. Paleopteran orders

1. Ephemeroptera: mayflies
2. Odonata: dragonflies and damselflies

Group II. Orthopteroid orders

3. Plecoptera: stoneflies
4. Grylloblattodea: rock crawlers
5. Orthoptera: grasshoppers, locusts, crickets, mole crickets
6. Phasmida: stick insects and leaf insects
7. Dermaptera: earwigs
8. Embioptera: webspinners
9. Dictyoptera: cockroaches and praying mantids
10. Isoptera: termites
11. Zoraptera: zorapterans

Group III. Hemipteroid orders

12. Psocoptera: book lice
13. Mallophaga: bird lice
14. Siphunculata: head and body lice
15. Hemiptera: bugs
16. Thysanoptera: thrips

Endopterygota Orders

Group IV. Panorpoid complex

1. Neuroptera: antlions, aphidlions, owl flies, mantispid flies
2. Mecoptera: scorpionflies
3. Lepidoptera: butterflies and moths
4. Trichoptera: caddisflies
5. Diptera: true flies
6. Siphonaptera: fleas

Other major endopterygote orders

7. Hymenoptera: bees, wasps, ants
8. Coleoptera: beetles and weevils
9. Strepsiptera: stylopids

Summary Cheat Sheet

• Phylum: Arthropoda.
• Class: Insecta or Hexapoda.
• Main subclasses: Apterygota and Pterygota.
• Apterygota: Primarily wingless, little or no metamorphosis.
• Pterygota: Winged or secondarily wingless, metamorphosis present.
• Pterygota divisions: Exopterygota and Endopterygota.
• Exopterygota: External wing development, no pupal stage.
• Endopterygota: Internal wing development, pupal stage present.
• Apterygota orders: Thysanura, Collembola, Protura, Diplura.
• Total commonly taught orders: 29.
• Examples of exopterygotes: Orthoptera, Hemiptera, Thysanoptera.
• Examples of endopterygotes: Lepidoptera, Diptera, Coleoptera, Hymenoptera.
• Exam tip: Learn the subclass differences first, then memorize the orders under Exopterygota and Endopterygota as grouped lists.

References

2 sources • [1] [2]

[1]

Fundamentals of Entomology

[2]

Insect Morphology and Systematics