Rob Partridge

[robpartridge]

Over the years, the White-letter Hairstreak has turned out to be more widespread in the intensively-farmed landscape of the Cambridgeshire fens than one might have expected. Some of the droves are very old, and where elm re-growth has survived, it's not unusual to find the butterfly. Colonies are small but somehow they survive. I've visited two new sites this weekend and found ova at both.

[David M]

Nice find, Rob. I presume they were on the lower branches?

[robpartridge]

David - yes, quite low down. One problem I find in these locations is that hedges have been flailed and most of the branches that have the flowers are out of reach. Also, no two stands of elm are quite the same when one examines them - there seems to be an infinite variation in the appearance of twigs, buds and flowers. White-letters probably favour some over others; I looked at some today which was south-facing, full of opening flowers and looked perfect - nothing. At another site, just three or four scrubby saplings had survived the disease, and you wouldn't give it a second look, but the ova were there.

[David M]

Thanks for that, Rob.

I need to do a bit of the same in my local woodland. There are plenty of elms and hopefully I will find a few ova.

[robpartridge]

Today I've searched some elms just a couple of miles as the butterfly flies from where White-letter ova have been found this year. These are different in form again - I cannot say for sure until later in the season, not being tree expert, but one group looked like Wych elm. That is supposedly the food plant of choice but despite an extended search, not ova were located. Certainly a spot I'll check again in July.

Here's an image of the flowers on today's elms - feel free to correct my id :

[robpartridge]

A bright spell this afternoon saw my second Peacock (and second butterfly) of the year - a fly-through in the garden, with no chance of a picture.

The search of local elms continued with a visit to a site with plenty of field elm, of the type which has colonies of White-letter within two or three miles. Lots coming into flower but no ova found today. The plan is to check all these sites in July to see how effective the ova search is in finding new colonies.

After this extraordinarily wet winter, the adjacent Ouse Washes reserve is deeply flooded once again:

[Padfield]

Hi Rob. Searching for ova is rewarding but not efficient, for lots of reasons. Not least of these is the fact that females often lay high in the tree - and as branches in winter, devoid of leaves, spring higher anyway, you have access to relatively few eggs. Back in 2019, I discovered that searching for caterpillars by UV (at night) from March to May is much easier. You can buy yourself a UV flashlight for very little, and will be amazed at how much you see when you illuminate an elm with it! The caterpillars fluoresce from the time they turn green - so late 2nd instar or early 3rd instar. With a powerful light, you can spot larvae high up in the tree above your head. Brown hairstreak larvae are equally easy to find at night - and very difficult in the day.

If you want to find which trees are hosting white-letter hairstreaks and which aren't, this is in my opinion by far the most reliable method.





If you do use this method, be sensitive to night-flying birds, like owls (or roosting birds). I'm sure it wouldn't be good for them to get an eyeful of UV.

Guy

[robpartridge]

Guy - by coincidence I had read a reference to this by you recently and had been wondering what it meant - now I know! Did you discover this yourself or find it in the literature somewhere? This is something I will certainly look into because at many potential sites there are no low branches at all. As a moth person as well, I am used to being approached and asked what I'm up to, shining them there lights about in the middle of the night...

Many thanks,

Rob

[Padfield]

Hi Rob. When I moved back from Switzerland to the UK, to look after my father, I had to do something to make up for the sudden lack of species. I’m not putting the UK down here - I love Britain and its wildlife - it’s just a big change, moving from a village in the Alps to Woodbridge, Suffolk. SO, knowing that some insects glow under UV, I bought a flashlight and started exploring. The very first thing I found was that white-letter hairstreak cats shine a brilliant blue-white in the night when you point a UV lamp at them. It transformed my understanding of where the butterfly was. I found it in the middle of the town on Siberian elm, by the river on wych elm, and at various other, random spots. Strange times: in 2020, I would go out after dark, knowing that a second walk was strictly illegal (those pandemic rules), and sneak around, trying to be invisible, shining a brilliant violet light into the trees …

Try it - you’ll be amazed.

Guy

[robpartridge]

Guy - clever stuff! Thank you - I'm researching torches already. As a matter of interest, do you know whether it works for other cats, such as the grass-feeding ones, eg Meadow Brown, Gatekeeper and so on?

As for the White-letter, it turns up in very odd places. I'm sure it disperses more freely than older textbooks suggest - or behaviour has changed since they were written,

Rob

[robpartridge]

The best sunshine of the year so far brought my fourth butterfly of the year, but somewhat surprisingly they have all been Peacocks. Yesterday's was an unusually large specimen which fled before I could get a picture; today's basked high up on the back of the house between two dormer windows, the warmest and most sheltered spot in the garden.

[Wurzel]

Great to see that Peacock Rob - looks in fine fettle after it's winter sleep Mind you it might want to head back to bed for lie-in for the next fortnight if the weather forecasters are to be believed

Have a goodun

Wurzel

[David M]

The best sunshine of the year so far brought my fourth butterfly of the year, but somewhat surprisingly they have all been Peacocks...

That is surprising, Rob. This species is usually the laziest of the adult overwinterers. Occasionally you see the odd one prior to March but to see four is most odd.

[robpartridge]

Thanks to Wurzel and David. Yes, it seems odd to me, only to have seen Peacocks. The first was on the 22nd of January which was vey early, according to my records. I think it helps to have woodland nearby, as it does with moth records at this time of the year, and I'm a long way from anything remotely resembling a proper wood.

Outside temperature here this afternoon is only 8.5C with a stiff north-easterly, so not much is going to be flying anywhere yet!

Rob

[robpartridge]

At last some sunshine, although there's a brisk north-easterly. Out of the wind, the garden thermometer showed 13C, so there's a chance of the second butterfly species of the year. A common lizard basked on the wood edging a raised border - we have a small colony on the track next to the house - and a few minutes after that a grass snake appeared out of some nearby brambles but didn't wait for a photo.

There were several Buff-tailed Bumblebees on the wing. One was exhausted but it recovered after my wife gave it some maple syrup on a spoon. There's always something new to see...

Finally, at 1.00pm, the season's first Small Tortoiseshell landed among the crocuses, but it too didn't wait around. The afternoon is clouding over and rain is forecast.

[Wurzel]

Great shot of the Bumble Bee Rob I find that I use these as an indicator - when they start flying you only need a little bit more sun usually and then the butterflies come out

Have a goodun

Wurzel

[David M]

At last some sunshine...

Send some of it my way, Rob!!

But for a brief half hour, we've been under a blanket of cloud between 10am and 3pm for over a week now. That said, bumblebees are still active. They don't seem to need the sunlight like butterflies do.

[robpartridge]

A Small White fluttering along in a few minutes of weak sunshine this morning was my third species of the year. I'm seeing very few butterflies at all, especially compared to those people posting from sites much further to the south.

[robpartridge]

A couple of hours of unexpected sunshine this morning, the 26th of March, brought a veritable flood of butterflies at last - well, 5 of 3 species. ! Small Tortoiseshell, 2 Peacocks and the season's first two Brimstones, both males. We're short of nectar sources at this time of year here, and most of the butterflies had been attracted to the blossom of a tall cherry laurel bush - something I haven't noticed before.

[Chris L]

Hi Rob. Searching for ova is rewarding but not efficient, for lots of reasons. Not least of these is the fact that females often lay high in the tree - and as branches in winter, devoid of leaves, spring higher anyway, you have access to relatively few eggs. Back in 2019, I discovered that searching for caterpillars by UV (at night) from March to May is much easier. You can buy yourself a UV flashlight for very little, and will be amazed at how much you see when you illuminate an elm with it! The caterpillars fluoresce from the time they turn green - so late 2nd instar or early 3rd instar. With a powerful light, you can spot larvae high up in the tree above your head. Brown hairstreak larvae are equally easy to find at night - and very difficult in the day.

If you want to find which trees are hosting white-letter hairstreaks and which aren't, this is in my opinion by far the most reliable method.





If you do use this method, be sensitive to night-flying birds, like owls (or roosting birds). I'm sure it wouldn't be good for them to get an eyeful of UV.

Guy

I bought a UV torch for about £12 after reading about the fun one can have with one in The Guardian. I read about it in The Guardian - not have fun shining it on The Guardian. Is there one that you can recommend? Mine was useless. I note that you used the word 'flashlight' whereas mine is a torch, which might be where I went wrong.