White-letter Hairstreak in Shropshire (Vice-county 40)

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	Winter surveying for the White-letter Hairstreak Satyrium w-album - Rob Thorne
	2007 records - Rob Thorne

THIS IS THE STORY FROM SHROPSHIRE (VC40)......

WINTER SURVEYING FOR THE WHITE-LETTER HAIRSTREAK - Rob Thorne
First published in the Comma No 67, Spring 2007. The newsletter of the West Midlands Branch

Winter can be a frustrating time for any naturalist and by the end of January spring and summer cannot come too soon. There are however a few things that can be done, one of which is egg hunting.

With a work-related morning in Ironbridge, Shropshire (a large area of mature woodland) I had the afternoon free to do as I pleased. I had seen on local records of the area, reports of White-letter Hairstreaks. So, with some last minute egg revision and some local knowledge of an area of un-surveyed Wych Elm, I set off up one of the many wooded dingles in the area. I arrived amongst the Elms and began my search. Within about an hour of searching I had located 6 eggs on two different trees.

A few days later a botanical survey, for a proposed sewage works, took me to Worcestershire, in the Malvern area. Walking up one hedgerow I noticed a lone flowering Wych Elm clinging on for dear life around a telegraph pole. To satisfy my curiosity I bent a couple of branches down and within a few minutes I had 2 eggs, followed by a further 3 on a tree some 200 yards further down the lane. I was both excited and intrigued, deciding then and there that I should investigate further in areas closer to home.

I was brought up in a village called Pulverbatch, situated in the foothills of the Long Mynd. The area is full of wooded dingles, copses and old hedgerows, perfect Elm hunting territory. With any spare time I had, I searched the local area for eggs and, although sceptical of finding any to begin with, all my forays were successful and my search began to spread further a field. To date (March 15th) the 20 trees/areas of Elm I have looked at have all produced eggs. Some of these sites are located around the Pulverbatch area but many were located simply by either driving along the roads of central and southern Shropshire or whilst out walking. As Elm is often associated with hedgerows driving is quite an effective way of locating the trees. Tree spotting from a moving car can be a hazardous process, so remember to keep at least one eye on the road! In addition to hedgerows, look for Elm around old-established settlements, especially churches, and in woodland. Tapping into local botanical knowledge can help to locate Elm sites as can looking at old tithe maps for Elm-related names.

Once the Elm has been located your search can begin. To start with you will scrutinize every lump and bump but, as with so many things searched for, the egg will become very apparent when you see it.

The egg itself is about the size of a pinhead and is 'flying saucer' shaped in appearance with a hairline, white fringe around its outermost perimeter. In the right light the top of the egg reveals an indentation (the part which the young caterpillar chews out when hatching). The egg is mid tone grey in colour, darkening towards hatching point to a much blacker colour. The grey egg shows up remarkably well against the black of the Elm buds and with a short amount of practice is easy to spot. Once you begin to see the eggs it will only take a few minutes to find them in future searches.

To speed up your search, look for branches receiving good sunlight. The tree itself will tell you if its suitable for breeding butterflies and if its receiving enough sunlight as it will have round black buds (the sign of a flowering tree). The leaf buds of Elm appear obelisk in shape and are located at the tip of the branch and sometimes leading up to and including the terminal bud. The easiest way to locate the eggs is by searching the very base of both the leaf buds and the round flowering buds. The butterfly also lays on the scarring of the previous years growth.

This scarring resembles the skin on a human knuckle. However the eggs are hard to spot due to their colouration resembling that of the bark. Until you 'have your eye in' it's best to stick to examining the buds. The most successful twigs appear to be the short flowering shoots which radiate from the main branch, like the rib bones of a cartoon fish. Limit your searches to the ends of branches (for 2ft from the tip) and you will have greater success. Also there is no need to twist and examine the underside of the branches as the eggs will almost always be laid facing skywards or slightly to the side, literally sunny side up.

In areas of more abundant Elm growth the butterfly seems to be more selective of the trees it lays on. It will still lay the odd egg here and there but a much higher density of eggs will be found on these special 'master' trees. Unless planning a thorough search avoid wind-exposed, shaded trees when locating these 'master' trees. Look at trees receiving good sunlight, preferably on the edge of or in a sheltered clearing.

Also trees in dips and hollows or at the base of a dingle or valley are likely to produce many eggs. Branches poking out through scrub into sunlight can be excellent, holding greater densities of eggs than other similar branches.

Egg © photo: Rob Thorne	Hatched egg © photo: Rob Thorne
1st instar larva © photo: Rob Thorne	1st instar larva © photo: Rob Thorne

Due to the butterfly's elusive nature and the fact that it was never a 'childhood butterfly' like the Tortoiseshell or Peacock we seem to overlook it, choosing Open Days at known sites to catch a glimpse. However, after a small amount of egg hunting you could locate your very own colony, which is something very exciting and will give you the opportunity to watch the adult any time you want during its flight season. One 'master' tree I discovered was only 15 yards from the house I grew up in and I've never seen an adult in my life! This is something I plan to put right come the summer.

There is a good chance of finding a colony close to where you live and locating a 'master' tree will offer you your very own viewing galley, come summertime. The butterfly appears to be highly mobile and able to support colonies on small areas of Elm, or indeed single trees. The ability of the Wych Elm tree to re-grow after the original tree has apparently died from disease (and English Elm to also sucker) means that colonies can hold on. Most of the trees I've looked at are young, albeit flowering, re-growth from diseased trees. With this in mind the chances of finding eggs where-ever there is Elm within the butterfly's geographical range (particularly in the West Midlands) on your Sunday walk, drive to work or even your very own back garden are excellent.

Flowering is clearly of importance, as the newly hatched caterpillars crawl into the opened flowers and take on the same pink and green colouration. The closed leaf buds (which open later) appear to be bypassed although the caterpillar will begin to eat the leaves when it is about half grown.

Finding a colony also allows you to send in a valuable record for a very elusive and under-recorded butterfly. In a time of Dutch Elm disease and hedgerow flailing the butterfly has many threats and many of these valuable unknown colonies, found in hedgerows and woods, are at considerable risk. Your records can also add to a greater understanding of the butterfly's distribution helping, ultimately, to assess a resurgence or decline in a species, which needs to be monitored.

Finally, if like me your car boot has a variety of butterfly related paraphernalia add a walking stick with a crook to your collection.

It can be a valuable tool to have, as many of the hedgerow Elms have a habit of growing their branches a couple of millimetres above finger tip height.

Above all enjoy your searching safe in the knowledge that winter won't be a butterfly-free zone anymore.

White-letter Hairstreak distribution (1km squares) as a result of Rob Thorne's egg and larva searches - 2007 Reference: Rob Thorne

Rob Thorne
June 2007

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