There can be few more uplifting moments after a long, dark, winter than to see a bright yellow brimstone butterfly fluttering through your garden; a sure sign that spring has arrived! Well, may be not, as the brimstone hibernates and if there is a sunny, mild day in the depths of winter they will emerge for a while before returning to their 'slumbers' when the weather deteriorates again. Brimstones are somewhat nomadic and individuals will travel far and wide through parks and gardens, along woodland rides, by hedgerows, almost anywhere there are shrubs and scrub. They are also long-lived for a butterfly and having survived the winter they mate in March and then continue to fly in to May and possibly June. The new generation of butterflies then hatch in late July and August. Whilst the male is bright yellow the female is a pale green, almost white, and are often mistaken for large white's even though they have no black markings on the wings.
In Dorset the weekly reports chart shows a sighting in January and in February 2018 but it is in March when they start to be seen regularly. There are a number of reports each week from week 7 onwards until week 17 at the end of April. There is then a gap until week 27 at the beginning of July although there is one report from week 20 in 2018. The newly emerging adults are then seen sporadically and in lesser numbers than in spring right through until they are driven back into hibernation for the winter.
The distribution map shows just how widespread brimstones are with reports from across Dorset but closer examination shows them scarce along the Purbeck coast and along the Fleet; this reflects the absence of woodland type habitats here and the lack of their larval food plant, buckthorn.
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