Butterfly Conservation's 2026 count recorded 77,151 butterflies and day-flying moths in Devon and 47,712 in Cornwall. It called the totals very good, but warned prolonged hot, dry weather could lead to a population crash; drought's full impact may not be clear until next year.
The charity said the strong totals were likely due to favourable spring conditions for caterpillars, followed by hot, sunny summer weather for adult butterflies. But it said drought may have withered caterpillar food plants before the caterpillars finished feeding.
Butterfly Conservation science chief Richard Fox said droughts in 1976 and 1995 severely affected butterfly populations, with some species never fully recovering. He said 80% of the UK's butterfly populations have declined since the 1970s. The charity urged people to plant trees and shrubs, store rainwater in water butts and leave some grass uncut.
