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I have been lucky to have seen all our hairstreaks close-up but I have knowingly seen only White-letters and Purples in flight near the tops of trees. As most of you know, White-letters are usually just dark-brown and smaller than Purples which often show a silvery tint at certain angles from the sun. White-letters show a little bit of silver on occasions but less so than the Purples.

Over the years I have seen hairstreaks over one ash tree on my local patch from at least 20 yards away so even with binoculars it is not easy to distinguish between the Purples and the Browns when they are jinking about. I know Browns are slightly larger and should show more orange but even Purples can be 'orangey'. Does anyone have any thoughts?

ATB

Peter

Hi Peter,
Having spent many years of my UK butterflying "career" studying hairstreaks, I couldn't resist replying to this post! My own experience differs a little from your observations.

Firstly, I assume that we are only talking about tree-top hairstreaks in flight, so we could probably remove Green Hairstreak from the discussion. Secondly, in my experience, appearances of hairstreaks in flight can vary considerably according to how fresh the individuals are.

So, for example, starting with Purple Hairstreaks, which are quite possibly the most numerous butterflies in many woodland settings - when fresh, these can appear quite dark in flight when viewed from below, but this dark appearance reduces considerably as the flight period progresses and individuals become more worn. The silvery flashes of the Purple Hairstreak as they catch the sunlight are absolutely characteristic in my opinion, especially when this species is viewed in early evening when activity is often at its most frenetic. I cannot say that I have seen similar silvery flashes from White-letter.

White-letter appear incredibly dark when freshly emerged, almost black in flight when viewed, but again this diminishes as they age and by the time they are a week or so old they may possibly be mistaken for Purples if only viewed at rest from a distance, without getting a good look at any markings.

I can't say that I have ever had any problem distinguishing between Purple and Brown when jinking about - they are like chalk and cheese - Browns always appear to have a much more orangey-gold colour to them, evident even at tree-top height, and even when quite worn.

Black hairstreak is a different beast again, but for different reasons!

The hairstreaks are intriguing insects to study and observe, all the more so because of the challenges of finding them!

Would be interested to hear of other peoples opinions.

I presume Browns are known at the site near you? I found taking pictures rather useful with these (I also do this to passing Whites when I'm recording on my transects so I can get an a confirmed ID). When Browns first started emerging at Bookham this year I took plenty of pictures of Hairstreaks fluttering around an Ash and zooming in you can get a good idea. Even when it's just a silhouette the wing shape is often enough to confirm ID

That's a great aerial silhouette shot there bugboy!

petesmith wrote:That's a great aerial silhouette shot there bugboy!

Thanks, one of several dozen I took that day !

petesmith wrote:Hi Peter,
Having spent many years of my UK butterflying "career" studying hairstreaks, I couldn't resist replying to this post! My own experience differs a little from your observations.

Firstly, I assume that we are only talking about tree-top hairstreaks in flight, so we could probably remove Green Hairstreak from the discussion. Secondly, in my experience, appearances of hairstreaks in flight can vary considerably according to how fresh the individuals are.

So, for example, starting with Purple Hairstreaks, which are quite possibly the most numerous butterflies in many woodland settings - when fresh, these can appear quite dark in flight when viewed from below, but this dark appearance reduces considerably as the flight period progresses and individuals become more worn. The silvery flashes of the Purple Hairstreak as they catch the sunlight are absolutely characteristic in my opinion, especially when this species is viewed in early evening when activity is often at its most frenetic. I cannot say that I have seen similar silvery flashes from White-letter.

White-letter appear incredibly dark when freshly emerged, almost black in flight when viewed, but again this diminishes as they age and by the time they are a week or so old they may possibly be mistaken for Purples if only viewed at rest from a distance, without getting a good look at any markings.

I can't say that I have ever had any problem distinguishing between Purple and Brown when jinking about - they are like chalk and cheese - Browns always appear to have a much more orangey-gold colour to them, evident even at tree-top height, and even when quite worn.

Black hairstreak is a different beast again, but for different reasons!

The hairstreaks are intriguing insects to study and observe, all the more so because of the challenges of finding them!

Would be interested to hear of other peoples opinions.

Thank you very much for your most informative reply, Pete. Yes, I just meant tree-topping hairstreaks which rule out the Greens. It is wishful thinking on my part to believe there are Brown Hairstreaks on my local patch but the fact that the ones on the ash appear different than the usual Purple Hairstreaks made me think. Yes I agree the condition of the butterflies has a lot to do with how they may look from a distance, e.g. do ageing male Brown Hairstreaks have a duller'or paler orange look in flight? Only once have I seen a tiny flash of silver on White-letters that I shouldn't have mentioned it .

ATB

Peter

bugboy wrote:I presume Browns are known at the site near you? I found taking pictures rather useful with these (I also do this to passing Whites when I'm recording on my transects so I can get an a confirmed ID). When Browns first started emerging at Bookham this year I took plenty of pictures of Hairstreaks fluttering around an Ash and zooming in you can get a good idea. Even when it's just a silhouette the wing shape is often enough to confirm ID
Brown Hairstreak, Bookham Commons #13.JPG

Thanks Paul. No confirmed sightings locally in the Stevenage area, unfortunately. A nice silhouette shot of one in flight. I must admit I hadn't thought of the wing-shape before so this is a very useful tip - something I will have to consider on future visits.

ATB

Peter