Wildlife experts have been warning about the alarming decline in insects for decades.

But the fall in numbers of bugs in Britain has now reached such a troubling extent that even motorists are noticing that their windscreens are clear of squashed flies, gnats, moths and wasps.

Where a trip in high summer would once have necessitated taking a squeegee to the front window, now the glass is largely clear, drivers are reporting.

Writing in The Telegraph letters page earlier this week, Michael Groom of Teffont Evias, Wiltshire asked: “Where have all the insects gone? My windscreen remains clear whatever the speed.”

Reader Richard Acland, of Chepstow, in Monmouthshire, also noticed the vanishing bugs, and said he believed insecticides on crops were wiping out insect life, adding: “This is why cars are not bug-splattered anymore.”