A month of butterflies
PUBLISHED: 06:25 25 August 2014
On a bright day all Norfolk's habitats shimmer with their ephemeral wings.
Also in grassland now are two species of skipper, small and Essex. Their caterpillars feed on grasses too but, although adults of these species are very similar indeed (so similar that the Essex skipper was only discovered in 1889), they have widely different life cycles. The small skipper, which has long been a common butterfly in Norfolk, overwinters as a caterpillar, just as the browns do. The Essex skipper, which has spread rapidly across Norfolk in living memory, overwinters as an egg, only emerging as a caterpillar in spring.
In some special types of meadow, rarer butterflies are to be seen. In the flower-rich grassland of old coastal sand-dunes, look at thistle and knapweed heads in July for nectaring adults of the beautiful dark green fritillary. The eponymous green is on the underside of the butterfly’s hind wing, and in truth it is more of a mossy blush. The insect’s upper wing, by contrast, is an exquisite chessboard of vivid orange and black. This species also overwinters as a caterpillar, feeding on the leaves of dog violets. Sadly, with the loss of unimproved grassland, it has hugely declined in Norfolk in the past century.
Rarer still is the gorgeous chalkhill blue. This small downy butterfly, with pale metallic blue wings bordered in white and smudgy black, is found at just one chalk meadow in north Norfolk where it was almost certainly introduced by an amateur lepidopterist. Its larvae emerge from overwintering eggs in early spring and feed exclusively on chalk-loving horseshoe vetch. Amazingly, these caterpillars secrete chemicals which attract ants; the ants tend them and protect them and are believed to go as far as hiding the pupae in their burrows. Adult chalkhill blues emerge in late July when huge clouds of them may be seen, like silver-blue confetti, blowing over the cropped grass.
July is also a fine time to head to the woods in search of butterflies. Where there are plenty of bramble flowers for adults to feed on and plenty of fragrant honeysuckle, which is the food-plant of the caterpillar, the lovely white admiral is on the wing now. With a darting flight on wings of velvet black, slashed by a bold line of white, this lustrous butterfly is unmistakable.
In just a few Norfolk woods a remarkable come-back is taking place. In very recent years the silver-washed fritillary, which had become extinct in Norfolk decades ago, has returned; its blousy orange adults are in flight in July, searching the woodland understorey for the common dog violets on which they will lay their eggs. Far above, in the tops of oaks, a tiny flash of blackish purple may be seen towards the end of the month. Overlooked, because no-one thinks to look for it in the crowns of the trees, this is the dazzling little purple hairstreak.
Whichever way you look in July, in whichever Norfolk habitat, if you choose a sunny day you are sure to see butterflies. And where there are butterflies there is fascination, there is child-like wonder, there is mosaic beauty, and there is joy.