Fossil insects – 400 million years of evolution

Insect fossils date back 400 million years – they witnessed the rise and fall of the dinosaurs and the evolution of almost every other group of land-based animals.

Fossil insects

Everything we know about ancient life comes from fossils. Insect fossils, however, are very rare. This is because the parts of animals that fossilize well are the hard parts. We know a great deal about dinosaurs because dinosaurs had hard bones, strong teeth and were usually large (even the smallest dinosaurs were the size of chickens). Insects, on the other hand, are small, fragile and lack teeth and bones.

Insects in amber

The most complete evidence we have of ancient insects comes from specimens preserved in amber or fossilized tree sap. Insects occasionally get caught in the sap that drips from trees. Sap hardens over time to form a plastic like substance. An insect trapped in amber will be perfectly preserved for millions of years.

Insect preserved in amber

Insect preserved in amber
Photographer: John Broomfield. Source: Museum Victoria

The fossil history of insects

Springtails, bristletails and the first true insects first appear in the fossil record in the Devonian, 410-354 mya. The first winged insects, the mayflies, grasshoppers and cockroaches, did not appear until the Carboniferous, 354-298 mya (spiders and scorpions also evolved at this time). Beetles, flies, true bugs, booklice, thrips, stoneflies, webspinners and lacewings (and frogs) all appeared in the Permian, 298-251 mya.

The Triassic (251-205 mya) heralded the arrival of the dinosaurs along with the dragonflies, stick insects, wasps and caddisflies, while earwigs, butterflies and moths accompanied the evolution of birds in the Jurassic (205-141 mya). Termites and fleas arrived just in time to witness the extinction of the dinosaurs in the Cretaceous (141-65 mya) and praying mantids first appear on the scene in the Palaeogene (65-25 mya). Finally, in the Quaternary (1.78 to the present), both humans and blood sucking lice appeared.

Fossil flea, Tarwinia australis

Fossil flea, Tarwinia australis; Early Cretaceous (c. 118 my old), Koonwarra, South Gippsland, Victoria.
Photographer: John Broomfield. Source: Museum Victoria

Why are insects so successful?

Insects have been an evolutionary success story for 400 million years because of several amazing adaptations:

Size. Bugs are small, which means they can fit into the ‘cracks and crevices’ of nature. They can live in places too small for larger animals and survive on tiny amounts of food that would not sustain larger animals.

Wings. Insects were the first animals to develop wings and for 90 million years they were the only animals to fly. Wings greatly improved their ability to escape predators, locate new food sources, migrate to new habitats and find mates. It took another 90 million years before the first pterosaur, a flying reptile, could fly and another 300 million years, before bats took to the air.

Metamorphosis. Metamorphosis allows insects to make dramatic and highly specialised changes between the larval and adult stages – for example, a caterpillar does not have wings, but an adult butterfly does. This allows adults and larvae to exploit different foods, seasons, habitats and lifestyles. So successful is complete metamorphosis, that it is part of the life cycle of over 85% of all insect species.

Fossil insect, Duncanovelia extensa

Fossil insect, Duncanovelia extensa, Early Cretaceous (c. 118 my old), Koonwarra, South Gippsland, Victoria.
Source: Museum Victoria

Insect relatives - spiders

The earliest fossil spiders date back as far as 300 million years. The oldest fossilised spider yet found in Australia was discovered in the Koonwarra fossil bed in South Gippsland, Victoria. It has been dated at approximately 118 million years ago (Early Cretaceous Period).

Fossil spider, Early Cretaceous

Fossil spider, Early Cretaceous (c. 118 my old), Koonwarra, South Gippsland, Victoria. This is the oldest fossil spider known from Australia.
Photographer: Frank Coffa. Source: Museum Victoria

Further Reading

An academic review of fossil insects in Australia is included in:

CSIRO (editor). 1991. The insects of Australia: a textbook for students and research workers, 2nd edition, vol. 1. Melbourne University Press, Carlton, Victoria.

Comments (5)

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Beth 11 June, 2009 12:01
This website has been very helpful with my science assignment. Thanks :)
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Dr. Fernando Hernández-Sánchez 20 February, 2010 08:11
Dear Sirs I have your photography “Insect preserved in amber" on the page WEB of museum Victoria. I am writing a scientific article about amber. May I use your Photo in my work? We will give you the recognition. Sincerely, Dr. Fernando Hernández-Sánchez
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Discovery Centre 24 February, 2010 10:39

Hi Dr Hernández-Sánchez - The Discovery Centre at Museum Victoria coordinates all requests for images owned by Museum Victoria as well as those that appear in our exhibitions, publications and websites. You can submit your request via our 'Image Requests' webpage. Before submitting your request, please read our image request guidelines.

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Talia 8 October, 2012 19:47
Hey, thank you so much for this sit, it has helped me with my extremely boring assignment to make it easy to understand and to make it interesting. I love fossils as a subject, but doing this was still a boring task, Thank You!
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josh 14 March, 2013 21:19
thanks this was VERY helpfull with my science project keep up the good work ;)
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