The Big Butterfly Count 2020 saw the lowest numbers of butterflies recorded in 11 years.
Wildlife charity Butterfly Conservation said the count from July 17 to August 9 saw a reduction in the average number of butterflies logged per count of -34% in comparison with 2019.
It was also the lowest average number of butterflies logged overall since the event began 11 years ago.
Dr Zoë Randle, senior surveys officer, said: “The fall in butterfly numbers this summer may be due to a number of factors. An unusually warm spring led many species to emerge earlier than usual, so we may have only caught the tail end of the flight period for many species.
“It’s important to look at butterfly trends over longer periods, so our scientists will be using these results alongside our other datasets to get a clearer understanding of what is happening.”