Graylings in Suffolk

by Rob Parker

The Grayling is the largest British member of the butterfly family of"Browns", and one of the

scarcest. We are lucky to have it in Suffolk,

although our populations are harder to find

than they used to be. ff you are interested in

seeing them, read on.

Grass sounds like an easily found larval host plant, but the Grayling is rather particular about the sort of grassland it frequents. It needs welldrained sandy soil, preferably slightly acidic. A glance at the UK distribution map in the Millennium Atlas of Butterflies in Britain & Ireland shows that it is found at mainly coastal sites, and hardly inland at all. The Suffolk Brecl<land provides something of an exception, as the soils here are very sandy, and akin to the Sandlings which is our most extensive habitat. The individual grass species vary from Marram on the dunes to Sheep's Fescue on heathland, but lush green fertilised pasture is totally unsuitable. Sandy soils often support conifers, and the Grayling is happy along the edge of the forest at Tunstall or Thetford, where sparse grass sprouts along the side of a stony track. Such a place often has heather too, which is the Grayling's favourite source of nectar.

The adult is on the wing in a single brood, from mid July through August, and well into September. Often there is a mass of heather at that time, but very little other blossom on the heath. It flies strongly, and often lands on the path a few metres ahead of you, only to disappear instantly; so effective is the camouflage of its undersides. Temperature regulation appears to be particularly important for the Grayling, and it basks not wings open like most species, but wings tightly closed and inclined away from the sun to catch the maximum heat on its undersides. When its body temperature has risen to the 30°C necessary for flight, it will either fly, or turn around until its body and wings are facing directly into the sun minimising heat uptake from then on. The cryptic markings on the hindwings are all that remains to be seen when the forewings are folded back, and the orange patch around the apical eyespot is· lost from view. Against sand, gravel or dead wood, the butterfly is extremely difficult to spot, even if you saw accurately where it landed; only when it flies off at your approach, does it become visible again. Taking nectar in the sun, it is less cautious, and may even open its wings partly, so look on the heather blossom for best results. Sometimes described as human friendly, they do seem to take an interest in passing humans, and bright T-shirts are said to attract them. A male alighted on Alex's pink blouse in the King's Forest this summer, and stayed for several minutes whilst I tried to focus the camera. What I did not see this year in West Suffolk, was any quantity of Graylings. In the recent past, I have found a dozen or more at a couple of spots on Lakenheath Warren, but this year it was just singles. I suspect that their distribution is polarising towards the Sandlings and the Brecks, leaving a bigger gap in the middle of Suffolk than is shown in the maps of Richard Stewart's The Millennium Atlas of Suffolk Butterflies - a visible change even over a 5-year period. [See map opposite for the latest picture) It has not been seen at Wortham Ling for some years, and our 2005 field visit sought to discover whether it was still present, but sadly failed to prove that it was.

Late in summer, the females visit clumps of grass and lay eggs singly, usually on a dried brown sheath, rather than on a growing blade. On one of our field trips a couple of years ago, some members were lucky enough to watch one laying an egg on apparently dead grass on the margins of Sizewell Beach. The larvae hatch in autumn, but do not feed much before hibernating, still as tiny caterpillars, at the base of a tussock. When fresh grass begins to grow in spring, they start to feed in earnest, climbing up the stems at night to eat the growing blades out of sight of predators. Moth

men searching fescue for Lunar Yellow Underwing larvae at night do find Grayling larvae at sites like Rendlesham Forest. Late in June they pupate in a silk-lined cavity at ground level, awaiting emergence some hot day in July. So, if you want to see Graylings, make a note in your 2006 diary now. In the west, visit Cavenham Heath NNR, the King's Forest, Lakenheath Warren (the public bits) or even Ramparts Field. Towards the coast, there is a wider range of opportunities around Minsmere, Dunwich and Sutton Hoo, to name but a few. Go on a fine day in July or August, and look out for patches of heather. Remember that Meadow Browns will be on the wing, and watch them first, noting their size and the appearance of their underwings when settled on the ground. When something larger flies by more strongly, watch it carefully - it could be Hipparchia semele.

And if it is, then be sure to note the date and precise location. The County Butterfly Recorder is waiting for your records! (butterflies@sns.org.uk ).

Grayling records 2000 to 2004 inclusive.

Note the polarisation towards the sandy areas of the Brecks and the Sandlings. Found in a total of I 08 tetrads over the five year period.

Written Autumn 2005

Key:

• 1 sighting • 2-9 max seen • 10+ max seen