a glorious morning for butterflies

The first of the spring’s butterflies is always a welcome sign; not the Peacock disturbed from its winter slumbers in the woodpile or the Small Tortoiseshell that has spent the winter in the cool of the spare room but one that has truly emerged from hibernation, brought to life by the rising daytime temperatures. The other morning, venturing into a different part of the forest to check out some ponds marked on the large scale map, I found not one but many butterflies on the wing, each one making the most of the early springtime warmth. All bar one of the two dozen or so individuals that I encountered in a little under two hours was a Brimstone, invariably a brightly coloured male, sulphurous yellow in colour.

That these individuals are on the wing so early in the year stems from the fact that they have chosen to overwinter as adults, fattening up on autumn nectar before finding somewhere suitable to pass the winter; in the case of the Brimstone the site will often be deep within an evergreen shrub. Just a handful of our butterflies overwinter as adults. Along with the Brimstone, Small Tortoiseshell and Peacock there are the Comma, Red Admiral and Large Tortoiseshell, the latter now effectively extinct as a resident. Other species pass the winter as caterpillars, eggs or as pupae, with each species overwintering at the same stage each year. There is an exception to this rule in the form of the Speckled Wood, which may pass the winter as either a caterpillar or a pupa depending upon late summer temperatures and their impact on larval development times.

The Brimstone has the longest adult lifespan of any British butterfly and individuals on the wing now may have emerged from their pupal stage early last July, and they may continue on the wing through into this June or even July. The brightly coloured males emerge from hibernation before the females (hence my seeing almost entirely males the other morning) and they can be wide ranging in their habits. Over the coming weeks the males will meet and court the pale coloured females, initiating what the great lepidopterist and illustrator F. W. Frohawk described so beautifully as ‘a prolonged dalliance flight in the sunshine’. The eggs will be laid towards the end of May, each one deposited singly on the underside of Buckthorn or Alder Buckthorn leaves.

It is an encouraging sign to see so many on the wing and equally reassuring to hear of other reports from across the county charting the emergence of other species. This might suggest that the cold weather has had little impact on their overwintering success, a good omen for the coming season.