www.ukbutterflies.co.uk

I caught up with White Letter Hairstreak for the first time this season. Could somebody please confirm the sex of these 5 individuals please ( I have tried to pick images where the abdomen is visible. I think the first 3 are female but am not 100% sure

Fantastic photos!
This is what I got -
1)Female
2)Female
3)Female
4)Female
5)Male
Photos 3 & 5 are great examples of the two sexes, especially as the tails remain intact, which helps.
I'm fairly certain I've got the sexes right but I'm always happy to be proven wrong. I've been around them enough this year, I estimate I've seen 50 this season.
If you haven't, check out my post covering the species - viewtopic.php?f=29&t=8319
All the best,
Jamie

Thanks Jamie That confirms what I thought. What other criterion are you using other than tails and abdomen size

jackz432r wrote:Thanks Jamie That confirms what I thought. What other criterion are you using other than tails and abdomen size

Photo number 1) Female - presence of a long tail confirms this.
photo number 2) Female - the top 'minor' tail is clear and intact, this protruding out from the wing margin, in males it's barely noticeable. This however is the real give away which I've discovered, the ratio of the head size to wing length, measured along the front edge of the forewing. This will sound weird but generally seven heads will fit along the edge of the wing in females, and around 5 heads for males. The starting point being at the top of the head, finishing at the very wing tip. (closed wings/ side view) This was originally discovered with my work on Purple Hairstreak which it also applies, distinguishing the sexes, wings closed. That kind of sorts the remaining photos out. Once you notice this difference the sexes become clear and exaggerated (when you have the opposite to compare), making females look like they have huge wings compared to their body. This will be covered and illustrated in my Purple Hairstreak article, once complete.
photo number 3) Female - 100% female as of long tails.
photo number 4) Female - a slither of the 'minor' tail is attached, again clearly protruding out from the wing margin.The ratio applies here again. Additionally the base colour on the females, though this individual is older is paler, males have a darker brown colouration.
photo number 5) Male - darker base colour to wings, short tails.
Ok maybe I do know the sexes

Thats fascinating, I've just gone through all my pictures with a ruler and managed to sex nearly all of them now . It would be very intersting if this fact holds with other Hairstreaks as well.
Thanks Jamie

bugboy wrote:Thats fascinating, I've just gone through all my pictures with a ruler and managed to sex nearly all of them now . It would be very intersting if this fact holds with other Hairstreaks as well.
Thanks Jamie

Wow, that's great! Yes just checked, the ratio applies to all our UK species of Hairstreak. ''nearly all'' I would be happy to help with the remaining photos if you like. If so perhaps send me a PM ?

Thanks Jamie
I put quite a lot of effort into finding White Letter Hairstreak this season, something which I intend to work on further over the winter and next flight season. Your excellent information is really useful thankyou
I look forward to reading your Purple Hairstreak article.

jackz432r wrote:Thanks Jamie
I put quite a lot of effort into finding White Letter Hairstreak this season, something which I intend to work on further over the winter and next flight season. Your excellent information is really useful thankyou
I look forward to reading your Purple Hairstreak article.

Great so do I, I'm really hoping to find my first White-letter Hairstreak egg over the next few months, I'll post anything if I'm lucky. My main focus is always Purple Hairstreak each year, however they had a bad year (weather) locally. That's when I switched my focus onto White-letter Hairstreak and finding new colonies near to me, the closest being on my road! As a result I was asked by Sussex Butterfly Conservation if I would like to take on the role of the Species Champion, so I said yes
Speaking of which I'll be doing a guided walk at Hollingbury Park, Brighton next year with the former Species Champion to look for the species. I'll post on my diary nearer the time when and where so anyone who would like to come can. Really pleased to hear, always happy to help. Thank you, I hope to have the Purple Hairstreak identification section complete and released by late spring, I'll send you a link to it once it's online.

I have often noticed that a blister like swelling on the underside leading edge of the male forewing is visible and which corresponds to the sex brand on the upper surface. It is generally more prominent in fresh males as in the example in the attached photo.

downland boy wrote:I have often noticed that a blister like swelling on the underside leading edge of the male forewing is visible and which corresponds to the sex brand on the upper surface. It is generally more prominent in fresh males as in the example in the attached photo.

Stunning photo, as is the individual, your point really is brilliantly illustrated. Especially so in the way the lighting shows up the area. Thanks for sharing

Wow, that's great! Yes just checked, the ratio applies to all our UK species of Hairstreak. ''nearly all'' I would be happy to help with the remaining photos if you like. If so perhaps send me a PM ?

Thanks Jamie, I've managed to work out them all now, I had a few previously sexed animals photographed at challenging angles!

Jamie Burston wrote:

downland boy wrote:I have often noticed that a blister like swelling on the underside leading edge of the male forewing is visible and which corresponds to the sex brand on the upper surface. It is generally more prominent in fresh males as in the example in the attached photo.

Stunning photo, as is the individual, your point really is brilliantly illustrated. Especially so in the way the lighting shows up the area. Thanks for sharing

Interesting point however This female I photographed this summer also has a similar blister like patch, although slightly less prominant

Bugboy, great to hear, yes foreshortening can be a problem in photos. Like you I also when back to my own photos and found the same regarding females, it is less prominent, probably as the patch doesn't have as much of a relief from the wing surface.. I can see how different lighting conditions play apart in the boldness of this blister patch, I imagine this wouldn't be a reliable indicator of the sexes out in the field. Brilliant discussion