Beauty of butterflies

A male brimstone in flight is a dazzling sight when its sulphur-yellow wings catch the sun

The butterflies of early spring are all hibernators. They were caterpillars last year and spent the winter as adults. You’ll see butterflies on the wing well into autumn but, as temperatures cool, their metabolic rate slows down dramatically.

If they’re tucked away somewhere relatively sheltered they’re more likely to survive. Hibernating butterflies have limited reserves of body fat, which they use slowly. So, it’s best if butterflies don’t reawaken at any time during hibernation.

In Britain, four species spend their winters hibernating – peacock, small tortoiseshell, red admiral and brimstone. Most hibernators don’t venture out until the end of this month, or during April.

Of the four, the consistently early riser is the brimstone, a striking butterfly that’s often on the wing from mid-March onwards. A male brimstone in flight is eye-catching – the upper sides of its wings are a bright sulphur-yellow when they catch the sun.

However, when they settle they close their wings and it’s the pale green underside that you see. That’s if you see it at all, because the colouring is an excellent camouflage when the insect chooses to sit on fresh, new foliage. The female doesn’t have the yellow colour that makes the male so striking. Her pale green shade can often mean she’s mistaken for a large white (or cabbage white).

The brimstone is a butterfly of woodland and hedgerows, where it can find buckthorn and alder buckthorn. Leaves of these two shrubs are the only ones that its caterpillars will eat.

It means female brimstones are relatively long-distance travellers. They’ll keep on the move until they find a buckthorn they can lay their eggs on, and so will often pass through gardens at this time of year.