WLH feeding damage

[ChrisStamp]

Just wondering whether anyone feels qualified to identify White-letter hairstreak feeding damage, vs damage from the various other things that eat elm leaves.

These photos were taken from around Dundee, which had its first reports of WLH this summer. As it is a colony that was found (as opposed to an individual butterfly), presumably it was the result of eggs laid last year so they existed there in spring as larvae and pupae, and larval feeding damage should be present if it could be found and identified (before the leaves drop). I've been looking at elm for survey sites next year and noting elms that appear to have been eaten. The question is, could any of this damage be identified as specific to WLH, and what level of confidence anyone would have?

[Jack Harrison]

Can't answer that one.
However, in a straight line, I am only about 100 miles further north. I have a smallish elm in the garden - last year had a Comma laying on it.

I am expecting Holly Blue any year but it never crossed my mind that I might get WLH first.

Jack

[Benjamin]

Hi Chris -
Here are a few examples of feeding damage from my own surveys that might help you make up your mind. Your final photo looks particularly good for final instar damage IMO but as you say, there are lots of other things that feed on elm so we can’t be 100%. The holes in the leaves are often formed by larvae (generally younger) nibbling on young leaves just as the buds burst and begin to grow - as they expand fully these nibble marks become windows of damage in the final leaf.

As I’m sure you are aware (and as much as I still value all these traditional field skills) we now have an extremely effective ‘cheat method’ that enables anyone to very easily locate WLH larvae in spring. With a UV torch you’ll very quickly be able to survey all the likely areas and map the distribution very accurately.

[ChrisStamp]

Thanks very much Benjamin, very interesting.

Jack, it is certainly an interesting time to be a butterfly observer in Scotland!

[Jack Harrison]

Chris:

Jack, it is certainly an interesting time to be a butterfly observer in Scotland!

Indeed, but with just two months to my 86th birthday, will I last long enough to see these new arrivals?

Still I've had a good run. 79 years since my mum caught a Peacock that got me into butterflies. Thanks Mum!

Jack

[Jack Harrison]

The follow up to the Mum's Peacock catch still amuses. Remember that I was just six-years-old at the time.

Mum told me that there were blue butterflies. I had never seen a blue butterfly. Some of you older people might remember Smith's Crisps. In the early days, they came with a little twist of salt in blue greaseproof paper. Mum had to buy several packets of crisps just to get the blue paper. They later became boring sachets of salt. She twisted them into something resembling butterfly wings and hung them to flutter in the breeze on the washing line.

The next year I saw my first real Common Blues.

Jack

[Padfield]

I agree with Benjamin that the last picture is very good for final instar feeding patterns. Compare with this picture, for example:



But equally, there are many other things that feed on elm and this is not a rare pattern.

Guy

[ChrisStamp]

Thanks very much Guy, it will be a very exciting new record if that one turns out to be WLH. Itching to find out - shame I have to wait until next year! I know that egg-hunting is a possibility but there are not many branches within reach and not much chance of fallen twigs, which I often rely on for Purple hairstreak egg surveys.