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A question for Susie, who has brown hairstreaks in her garden ( ), or anyone else who has experience of the larvae.

At lunchtime today I casually checked some local blackthorn and found I had a colony of brown hairstreaks just 3 minutes walk from my house. This was a big surprise - I didn't know they came up the mountain this far (1000m). It also means that when the eggs start hatching I should be able to check them daily and get some photos of the larvae. What I'd like to know is:

When do they leave the egg (in relation to flowering, leafing &c.)? The flowers come out before the leaves - do the caterpillars wait for the leaves to appear?
Where do they feed? Undersurface, uppersurface, &c.? Do they stay on the same twig they hatched on? Is it worth marking the egg twigs?
Do you have any tips on finding the caterpillars (bearing in mind this might be a very small, satellite colony)?

I've never had this opportunity before and I don't want to miss it!

It was a great day today - I also had my first ever post-hibernation Camberwell beauty for the local patch, as well as large tortoiseshell, small tortoiseshell, brimstone, peacock and red admiral, all on a lunchtime walk.

Guy

Today's eggs:

Guy,

Prior to hatching the larva will snip the micropile and rest with it's head clearly capsule visible as a black 'spot' in the centre of the egg. Upon emergence the larvae bore into a developing leaf bud. Usually timed perfectly so that the bud has 'broken' but the leaves remain tightly rolled.

As the larva (and the leaves) develop, the young (now green) larva proceeds to eat leaves from the edges (leaving scallops) and rests on the under surface.

Older larvae are pretty mobile and will crawl some distance to find choice leaves with a suitable aspect.

Prior to pupation the larvae darken and descend to the litter to pupate.

Brown hairstreak larvae are not usually cannibalistic, unlike many of their close relatives.

Keep us posted...!

Felix.

Thanks Felix - that's very useful information.

I'll be in India until 12th April, when our summer term starts, but I don't think there's any chance of the leaf buds bursting before then so I won't miss anything. With the daylight saving it will be light enough for me to check the eggs daily on my walk home from school and I will certainly keep you posted if I photograph anything interesting!

Guy

Hi, just to add...The BH i have reared have pupated on the bush and not on the ground.

Hi Guy,

Just wanted to say apologies for not replying, I have only just seen your post. As Felix has answered your questions better than I could I shall just look forward to your reports as they develop

It can't be long now! Here are a few of my local eggs today (25th April), with greenery bursting out all around them!! The altitude is about 1000m.










(There are two eggs in that last picture)

If I check these daily I hope I should be able to catch a larva or two...

Guy

Felix wrote:Prior to hatching the larva will snip the micropile and rest with it's head clearly capsule visible as a black 'spot' in the centre of the egg.

This morning, one of the eggs was at just that stage:



I shall go back this evening and see if it is still like that or if it has come out during the day. Perhaps they only come out at night...

Elsewhere this morning it was clear I had missed at least one of the big moments:



I searched without success for the larva, or evidence of it, though I was very careful not to disturb the eggs or leaves.

More pics to come, I hope.

Guy

The black-head egg hatched between 10.30am and 5.45pm today. And no sign of the larva anywhere now. This is clearly a six-pack job (camping chair, six-pack of beer, sit it out) but unfortunately I have to work during the day.


(5.45pm)

Guy

Roughly 50% of the eggs have now hatched and I still haven't had a sniff of a larva. I think they must make a bolt for freedom very quickly, as I have spent a long time waiting and watching - I kept one black-headed egg under surveillance for two hours yesterday evening without seeing any change, but by the time I got back from school today he had gone. I can find absolutely no sign of any larvae on leaves near the empty eggshells. Perhaps they will be more visible when they are bigger.

You can easily identify hatched eggs with the naked eye. There are two in this picture:



The larvae always emerge through the micropyle, which they snip into a gaping hole:



I've probably got just a few more days to see if I can catch a caterpillar coming out. There are plenty of eggs left, but I still have the day job.

This one is moving soon, I think:



The two remaining eggs here look as if something is going on inside them:



Guy

You have my sympathy, Guy. I know the feeling. I've been looking for the caterpillars but although there are a lot of nibbled blackthorn leaves I can't find a brown hairstreak cat anywhere.

Amazing photos, btw.

Looking at those images of the eggs with holes where the cats have emerged, don't the caterpillars usually eat the egg shell? I thought they usually did as it gives them enough to sart devolpment then they move onto the buds of the plant. I thought also if some didn't eat their eggshell, they wouldn't survive.

Nice photos Guy. Shame this one doesn't exist in Ireland, although later this year I may be going to look for Purple Hairstreak which is rare in Northern Ireland (have to check all the oaks around my area to see if any exist there, possibility, but no gaurentees)

Finally, I think I've found one of them!! I wasn't sure at first, because the lighting conditions (evening + very grim weather) made it difficult to see or photograph the little creature, and there are loads of other things living on the blackthorn, but I am quite confident now. Confirmation would be very much appreciated:





I didn't expect the dorsal hairs/spines visible in the second picture. Everything else seems to match the patterns in the pictures, given that this is a very young larva and the pictures show more mature ones.

Guy

That's 100% BH for me Guy!!
To my eye, they're a bit longer than usual for a lycaenid... do you think?

Glad you agree, Paul. Yes, it did look a little less squat than I expected, but it is still very much a baby and as I say, all the pictures are of rather more mature cats. This was about 3 mm long. You surely don't have these up in Richmond, do you? Have you seen them down south?

Guy

No, none up here, been shown them before though.

Excellent news, Guy

The pics look spot on to me. Here are a couple of mine from last year for comparison. The first one was taken on 18th April last year not long after they emerged and the second one about 10 days or so later. You can see how hairy they are.

Brilliant! Thanks Susie!

Guy

I've been digging through my old nature photos from last year and I've found an even earlier one. This was taken on 13th April, I would guess this was a day or two from them having hatched.

And absolutely no doubt whatsoever you have found what you were looking for, well done!

I just want to add one more pic to your thread, I hope you don't mind, this is right the other end of the process. Towards the end the caterpillars crawled down the plants to the ground and turned pink before shedding that skin and turning into pupa. This is from the inbetween stage and I've not seen anything else quite like it. It also gives you another good view of all those hairs.

That's very interesting! Less than a week after I found the first hatched egg I took this photograph:



It had been pouring with rain and was beginning to rain again, so I didn't hang around for more piccies. But back home I concluded this just didn't look enough like a brown hairstreak, and there were so many other eggs and strange creatures crawling over the blackthorn I left it at that. Looking at your picture of the young caterpillar I'm wondering again.

I really hope I'll be able to follow the process all the way through, like you, but that does depend partly on what happens when the farmer puts animals back in the field for the summer. Cows are very curious creatures. If my lying on the ground looking up through the leaves into the light (my new way of finding things on the leaves - sillhouettes - clever) causes them to come over and trample everything (including me) I'll let the hairstreaks alone...

Guy