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Insect Evolution in Different Era

  • Just as the PALEOZIC is often called the age of the trilobite, modern time is often called the "age of the insect".
  • The insect fossil record extends back some 400 million years to the lower DEVONIAN.
  • The pterygotes (winged forms) underwent a major radiation in the CARBONIFEROUS.
  • The Endopterygota underwent another major radiation in the PERMIAN.
  • Survivors of the mass extinction at the PT boundary evolved in the TRIASSIC to what are essentially the modern Insecta Orders that persist to modern times.
  • Most modern insect families appeared in the JURASSIC, and further diversity probably in genera occurred in the CRETACEOUS.
  • It is believed that by the Tertiary, there existed many of what are still modern genera; hence, most insects in amber are, indeed, members of extant genera.
  • What seems most fascinating is that insects diversified in a brief 100 million years (give or take) into the modern forms that exist with minor change in modern times.
  • Insect evolution is characterized by rapid adaptation with selective pressures exerted by environment.
  • Rapid adaptation is furthered by their high fecundity. It appears the rapid radiation's, and to this day the appearance of new species result in insects filling all available environmental niches.
  • Insect evolution is closely related to the evolution of flowering plants.
  • Insect adaptations include feeding on flowers and related structures with some 20% of extant insects depend on flowers, nectar or pollen for their food source. This symbiotic relationship is even more paramount in evolution considering that about 2/3 of flowering plants are insect pollinated.
  • Insects are also vectors of many pathogens that may even have been responsible for the decimation or extinction of some mammalian species.
  • Compared to other organisms, insects have not left a particularly robust fossil record.
  • Other than in amber, most insects are terrestrial and only preserved under very special conditions such as at the edge of freshwater lakes.
  • Yet in amber, age is limited since large resin production by trees developed later than the ancient insects.
  • Interestingly, while some 1/3 of non-insect species are extinct fossils, it is believed that only 1/100th insects are extinct fossils.
  • *Endopterygota is comprised by the orders of insects which are holo-metabolous, have larval (vs. nymphal) stages, and are separated from the Exopterygota in that they have an internal vs. external wing development.
  • Examples from this group are the Coleoptera, Lepidoptera and . Not included with this group are the Hemiptera, Homoptera, Orthoptera and Isoptera.

Note: red font indicate different eras


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Please note that this is the opinion of the author and is Not Certified by ICAR or any of its authorised agents.