Scientists at the University of York have revealed that the 1976 drought is the worst extreme event to affect butterflies and moths in the 50 years since detailed records began.
The summer of 1976 saw standpipes in the streets and billions of seven-spot ladybirds swarming in search of food.
Since then, the UK has warmed by a full degree Celsius and experienced numerous bouts of extreme weather, from heavy rainfall and flooding to heatwaves and drought; yet no single year has caused so many butterfly and moth species to crash simultaneously.
"It was the culmination of a two-year event."
said Dr Phil Platts, Postdoctoral Research Associate in York’s Department of Biology and co-author of the study.
"Hot and dry conditions stretched back to the spring of 1975.
The study also looked at the impact of extreme weather on birds, determining that the cold winter of 1981-82 had the biggest effect on their numbers.
"This seems to be truer of short-lived species that can multiply rapidly, like butterflies and moths, than of the birds we studied."
said Professor Tom Brereton, co-author and Head of Monitoring at Butterfly Conservation.
However, global warming is projected to increase the frequency of extreme weather events such as heatwaves and drought, and it is likely that some of these will generate even greater population changes than we have seen so far.