Now the group of German entomology enthusiasts can boast a world-class scientific treasure: evidence of what is described as one of Earth’s worst extinction phases since the dinosaurs vanished.

Insects, which comprise two thirds of all terrestrial species, have been dying off at alarming rates, with disastrous impacts on food chains and habitats, researchers say.

The home of the Amateur Entomology Society of Krefeld on the Dutch border is a former school building where thick curtains block out the sunlight.

Inside in glass cabinets are stored thousands of butterflies, their wings bleached by time, along with exotic fist-sized beetles and dragonflies, brought back from around the world by amateur collectors.

Treasure trove

Traditionally “entomology was mainly about drying and collecting rare specimens,” says the society’s president Martin Sorg, wearing John Lennon-style glasses, a multi-pocket jacket and sandals.

He and an army of volunteers have over the years gathered as many as 80 million insects that are now floating in countless ethanol bottles.