INTRODUCTION TO PHYLUM ARTHROPODA
1. The word 'Entomology' is derived from two Greek words 'Entomon' means insect and logia' means knowledge. Entomology is the scientific study of insects.
2. Insects came into existence 350-500 million years ago.
3. Insects originated during Devonian period, Paleozoic era.
4. The earliest known fossil insect, Rhyniella praecursor (Collembola) was discovered in Scotland by Hirst and Maulik (1926).
5. First winged insects originated in Carboniferous period.
6. Phytophagous insects originated during Carboniferous period.
7. Highly advanced insects like Lepidoptera, Diptera evolved during Mesozoic era.
8. The last to appear is the order Lepidoptera during Cretaceous period (Mesozoic era).
9. Insects are grouped in Phylum Arthropoda, Subphylum Uniramia, Class Insecta/ Hexapoda.
10. Largest phylum is Arthropoda. Second largest phylum is Mollusca.
11. 3/4th of animal species comes under Phylum Arthropoda.
12. The word 'Arthropoda' is a combination of two Greek words 'Arthro' means jointed and 'pod' means foot.
13. Arthropods are schizocoelomates. Body cavity (coelom) is formed by splitting the mesodermal embryonic tissue. ?
14. Phylum Arthropoda has seven main classes:
1. Onychophora e.g. Peripatus.
2. Crustacea e.g. Prawn, crab, wood louse.
3. Arachnida ee Scorpion, spider, tick, mite,
4. Chilopoda eg. Centipedes,
5. Diplopoda eg. Millipedes.
6. Trilobita (an extinct group)
7. Hexapoda or Insecta e.g. Insects,
15. Peripatus is a living example which shows that arthropods are derived from annelidan stock
16. In Onychophorn, respiration is cutaneous and nephridia are the organ of excretion.
17. Crustaceans have 2 pair of antenna and stalked eyes. They have gills for breathing and green glands for excretion. They have minimum 5 pairs of biramous legs.
18. In Arachnida, antenna is absent, has 4 pair of legs, booklungs are the organs of respiration. Malphigian tubules and coxal glands are the organs of excretion.
19. Chilopoda has one pair of leg per segment, poison glands are present in front pair of legs. Respiration is through trachea and Malphigian tubules are the organs of excretion.
20. Diplopoda has two pair of legs per segment. Respiration is through trachea and Malphigian tubules are the organs of excretion.
21. The word 'Insect' is derived from Latin. Insectum means 'animal with a notched or divided body
22. Phytophagous insects (26%), saprophagous and predaceous insects (31%) contribute a higher share in abundance of species in major taxa excluding algae, fungi and microbes.
23. Heaviest insect is Goliath beetle.
24. Biggest insect is the giant atlas moth. Attacus atlas.
