Sexing Hairstreaks

[Max Anderson]

Have been sitting on this since July, but only just remebered that I had it to share...

Very interested to learn how others go about determining the sex of Black Hairstreaks based on underwing morphology. I've read about various characteristics being used, but it's something I've struggled with. Would appreciate any input from those that are confident in their ID. I know some of the other hairstreaks can pose similar issues, so could also repeat the exercise for other spp. in future, e.g. WLH.

All images used have been taken from the Black Hairstreak UKB species page. If anyone has any issue with me using their image, please let me know (with apologies in advance)!

[bugboy]

I use a few aspects. The main one which is probably the most well known is the length of the tails, I find this is not as clear cut as in the WLH, (obviously only useful if they still have them!) Another aspect is the roundness of the outer margin of the forewings. Females tend to be rounder, males more straight giving the wing a more angular look (something that use for quite a few other species, particularly other lycids). Sometimes you can also make out the males scent brand showing through if the wings catch the sun right.

If PhiliB sees this thread I'm sure he'll have some good advice.

[bugboy]

There was also another guy who used to be active on here (his name now escapes me and its been a few years since he posted) who found that comparing the size of the butterflies head to the length of the leading edge of the forewing was pretty accurate. I can't remember the details or which way round it was but for the sake of argument it was along the lines of males forewing was 10 heads long and females were 9. The suggestion was it was accurate for all the hairstreaks.

[bugboy]

So now I’m on my computer at home I’ve had a go at trying to sex each image twice, each time using only a single feature: Firstly, the length of the tails and secondly the shape of the forewing (specifically how curved the outer edge is). Also, on any that I think I can see the shadow of the scent brand I’ve added a third. It’s actually very difficult to focus on just the single aspect, my natural instinct is to take in the whole insect and judge on its general jizz.

1) M M M
2) M M M
3) M M
4) F F
5) F F
6) F F
7) F F
8 ) F F
9) F F
10) F F
11) F F
12) F M
13) F F
14) M M M
15) M F
16) F F
17) M M
18) F F
19) F F
20) F F
21) M M
22) F F
23) M M
24) F F M
25) M M
26) F F
27) F F
28) F F
29) F M
30) F F
31) F M
32) F F
33) F F
34) F F
35) M F M
36) F F
37) M F M
38) F M
39) F M
40) F M
41) M M
42) M F
43) F F

It’s difficult to be objective on the final one since it does seem to be oviposturing!

Also I’ve remembered the name of the chap I mentioned in my previous post, Jamie Burston.

Anyway, I'll stop hogging this post now