First recorded

In a location that you monitor regularly (at least once a week), record the first time you see a live, active brimstone outdoors.

Overwinters as an adult, we are recording the first emergence dates of these adults.

Active very early in the year, they appear from March to early April.

There is a single brood each year, observations made after the end of May are likely to be the offspring of the overwintering butterflies and should not be recorded.

Available historic data: we have individual records from 1770-1810 and 1846-1906. We have some data from 1907-1955 and 1965-1999