Researchers examined soil samples for pollen, spores, pieces of plants and insect legs - organic debris that might otherwise have been considered "pond scum" when it was trapped in sediment during cataclysmic earth events 200 million years ago.
The slides of rock samples drilled in the German countryside included some material that looked similar to features found in insect wings.
However, these types of moths and butterflies - known as Lepidoptera - were long posited to have evolved 50 to 70 million years later, during the Cretaceous period when the first flowering plants emerged as their prime food source.
"The consensus has been that insects followed flowers," said Paul K Strother, from Boston College in the US.
"But that would be 50 million years later than what the wings were saying. It was odd to say the least, that there would be butterflies before there were flowers," said Strother, co-author of the study published in the journal Science Advances.
In the absence of flowers, primitive butterflies and moths, known as the Glossata, developed sucking proboscis to find nutrition by drawing off water droplets from the tips of immature gymnosperm seeds.
"What we've found is that these butterflies and moths with mouth parts were feeding on pollen droplets of gymnosperm seeds - from conifers related to pines, seed plants without fruits and flowers. They were feeding off the cone-borne seeds - mainly as a source of water," said Strother.
Even Charles Darwin called the mysterious evolution of flowering plants "an abominable mystery."
Scientists have reckoned that flowering plants preceded the insects that fed off of them.
However, researchers have gradually started to piece together evidence that moths and butterflies existed earlier than the Cretaceous period, which began 145 million years ago.
The team findings shed new light on the classic example of co-evolution: the evolutionary interplay between pollenating insects - flies, bees, wasps, butterflies and moths - and angiosperms, or flowers, Strother said.
"Our discovery does not change this, but instead, it demonstrates that the Glossata - which gave rise to the Lepidoptera - evolved earlier by a feeding adaptation to the gymnospermous ovules, or the pollen droplets," said Strother.
"These insects later transferred their feeding preference onto angiosperms, and, as a result, ended up co-evolving with flowers where they function to transfer pollen as they feed on nectar," he said.
Researchers assembled a portfolio of samples containing fossilised remains of moths and butterflies to carefully establish the presence of Lepidoptera in earth samples from a region where the cataclysmic transition between Triassic and Jurassic is preserved in rock.
The mass extinction event 201 million years ago wiped out an estimated 35 per cent of all species, which makes the survival and diversification of Lepidoptera all the more remarkable.
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