The number of flying insects has plummeted by 75 per cent in the last 25 years, according to a study that suggests we are approaching an “ecological Armageddon”.

The implications for humanity are profound, with insects providing an essential role for life on earth as pollinators of plants and prey for larger animals.

Although it was known species such as bees and butterflies were declining, scientists were left shocked by the drop in numbers across nature reserves in Germany.

While no single cause was identified, the widespread destruction of wild areas for agriculture and the use of pesticides are considered likely factors. Climate change was also cited as playing a potential role.

Dave Goulson, professor of life sciences at the University of Sussex and the study’s co-author, said: “Insects make up about two-thirds of all life on Earth but there has been some kind of horrific decline.

“We appear to be making vast tracts of land inhospitable to most forms of life, and are currently on course for ecological Armageddon. If we lose the insects then everything is going to collapse.”

The researchers were able to rule out weather events and changes in the landscape of nature reserves as possible causes.

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The results are based on the work of dozens of amateur entomologists across Germany, who have been catching insects in malaise traps – large tent-like structures that funnel insects into a collecting cylinder.

When the weight of the samples taken from the malaise traps was compared to samples taken in 1989, an average loss of 76 per cent was recorded. The decline was even starker in summer – when insect numbers are at their highest – with a loss of 82 per cent.

A malaise trap at a nature reserve in Germany (Plos One)

“The fact that the number of flying insects is decreasing at such a high rate in such a large area is an alarming discovery,” said Hans de Kroon, an ecologist at Radboud University who led the new research.

Scientists believe the fact the declines were recorded in well-managed nature reserves makes the results even more troubling, as numbers outside them, where wildlife has less or no protection, are likely to be even worse.

Mr Goulsen said a possible explanation would be insects dying when they fly out of nature reserves into farmland “with very little to offer for any wild creature”.

Wet summers drive five British butterflies close to extinction Show all 5 1 /5 Wet summers drive five British butterflies close to extinction Wet summers drive five British butterflies close to extinction Pearl-bordered fritillary (Boloria euphrosyne) ALAMY Wet summers drive five British butterflies close to extinction Wood white (Leptidea sinapis) ALAMY Wet summers drive five British butterflies close to extinction Lulworth skipper (Thymelicus actaeon) Wet summers drive five British butterflies close to extinction Duke of Burgundy (Hamearis lucina) ALAMY Wet summers drive five British butterflies close to extinction High brown fritillary (Argynnis adippe) ALAMY

“But exactly what is causing their death is open to debate. It could be simply that there is no food for them or it could be, more specifically, exposure to chemical pesticides, or a combination of the two,” he said.

A UN report in March warned that pesticides, which are “aggressively promoted” by chemical industries, were found to have “catastrophic impacts on the environment, human health and society as a whole”.

It said the idea that they were necessary to feed the world’s growing population was “inaccurate and misleading”.