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Holly Blue: variation in female markings between broods
Posted: Tue Jan 14, 2020 11:44 am
by millerd
There is a generally accepted clear difference in the degree of black marking between the first and second brood females in Holly Blues, the latter having markedly more black than the former. I have posted examples of third brood females over the last few years, and several people have asked me recently whether there is any noticeable difference between second and third brood examples. As a consequence I thought I would look at a selection from all three broods and see just what the extremes are. The periods shown for the broods are an approximation, between the first sighting (usually a male) until the last (usually a female).
First Brood: from the end of March until the end of June
![HB7 020519.JPG (2.53 MiB) Viewed 820 times 2nd May](./files/thumb_9839_372e6226935da4055daabf155828857c)
- 2nd May
![HB13 040519.JPG (2.66 MiB) Viewed 820 times 4th May](./files/thumb_9839_ceb682084461d836c9e6c51487c09a4f)
- 4th May
![HB1 160519.JPG (1.64 MiB) Viewed 820 times 16th May](./files/thumb_9839_08442bfa45d4e28532ce35915545ffd0)
- 16th May
![HB2 200519.JPG (3.88 MiB) Viewed 820 times 20th May](./files/thumb_9839_34a7bb765d48ba05744217ea2da579e7)
- 20th May
![HB2 240519.JPG (2.64 MiB) Viewed 820 times 24th May](./files/thumb_9839_c5c1f2c74acb000c1459651e0d242a44)
- 24th May
![HB9 300519.JPG (2.8 MiB) Viewed 820 times 30th May](./files/thumb_9839_c562d064c0d290302a67f9d3168387aa)
- 30th May
![HB7 050619.JPG (1.26 MiB) Viewed 820 times 5th June](./files/thumb_9839_61d53424fe8fd58ed15277eb850ad127)
- 5th June
The last female seen from this brood was found laying on 30th June
![HB1 300619.JPG (1.76 MiB) Viewed 820 times 30th June](./files/thumb_9839_165443fd33b926702b1738ceaefb224e)
- 30th June
As can be seen, these examples cover May to mid-June, though worn individuals were found for another couple of weeks. The first males from the second brood appeared about a fortnight later, in mid-July.
The next post will contain second brood examples, and the final one the third brood.
Dave
Re: Holly Blue: variation in female markings between broods
Posted: Tue Jan 14, 2020 11:59 am
by millerd
Re: Holly Blue: variation in female markings between broods
Posted: Tue Jan 14, 2020 12:34 pm
by millerd
Third Brood: October-November
![HB3 091019.JPG (1.56 MiB) Viewed 817 times 9th October](./files/thumb_9839_141e7ce57f6296b6e5713454c93ff2de)
- 9th October
![HB34 101019.JPG (2.13 MiB) Viewed 817 times 10th October](./files/thumb_9839_844ab3144aefb4241cdd46cac2583510)
- 10th October
![HB2 221019.JPG (2.07 MiB) Viewed 817 times 22nd October](./files/thumb_9839_0e228232db343b86ed9b66580bbc7b3f)
- 22nd October
![HB32a 301019.JPG (4.61 MiB) Viewed 817 times 30th October](./files/thumb_9839_eab4dec4aa2c13485537f7c7095126e5)
- 30th October
![HB23 311019.JPG (2 MiB) Viewed 817 times 31st October](./files/thumb_9839_01b11e636d8233b766c3ca9c64de10bd)
- 31st October
The last 2019 sighting (a male) was on 27th November. Here are some females from November in previous years for comparison in the absence of a 2019 November female.
![HB1a 161117.JPG (4.88 MiB) Viewed 817 times 16th November 2017](./files/thumb_9839_659d3e9c02e0bbf59c2d0257db9e0a0e)
- 16th November 2017
![HB7 141118.JPG (3.1 MiB) Viewed 817 times 14th November 2018](./files/thumb_9839_9e3edf2797f0e7006cd73e1e8fc3774b)
- 14th November 2018
Looking over the three broods it can be seen that within each there is quite a bit of variety (the various examples all seen on 17th August demonstrate this). Though the general rule remains true that the second has heavier black markings than the first, some of the first nearly approach the second in this respect. What can be seen however, is that the third brood females do not differ particularly from those of the second.
What actually determines the degree of black marking is difficult to pin down. The conditions under which the pupa develops are no doubt significant, but these will vary enormously with the only definite factor being that the spring emergence will have spent a relatively long time in cool conditions, and will undergo the period of the year when day-length increases markedly. The other two broods experience a shortening day, not much for the second but much greater for the third.
What it is that triggers the third brood itself, particularly those that appear right into November, is also mysterious. Days are very short, sunshine relatively weak even if the air isn't too cold, and there may even have been a few slight frosts. Why do some pupae not enter hibernation as the majority must?
I hope this has been an interesting study - even if it is not particularly conclusive, it may provide food for thought at least.
Dave
Re: Holly Blue: variation in female markings between broods
Posted: Tue Jan 14, 2020 12:49 pm
by Pete Eeles
Excellent report, Dave!
millerd wrote: ↑Tue Jan 14, 2020 12:34 pm
the third brood females do not differ particularly from those of the second.
Thanks for the confirmation!
millerd wrote: ↑Tue Jan 14, 2020 12:34 pm
What actually determines the degree of black marking is difficult to pin down. The conditions under which the pupa develops are no doubt significant
My understanding is that the cells that contain the pigments are laid down shortly after the pupa has formed - some aberrations are artificially created by exposing them to extremes of temperature just after the pupa has formed. Since those formed at the end of the year will be in cooler temperatures (on average) than the offspring in the summer, then the environmental conditions (higher temperatures) may be the cause of the differences in colour.
I feel an experiment coming on
millerd wrote: ↑Tue Jan 14, 2020 12:34 pm
What it is that triggers the third brood itself, particularly those that appear right into November, is also mysterious.
With a 3rd brood becoming an increasingly frequent occurrence, and with second broods of other species more regularly appearing, it's almost certainly due to temperature I would suggest.
millerd wrote: ↑Tue Jan 14, 2020 12:34 pm
I hope this has been an interesting study - even if it is not particularly conclusive, it may provide food for thought at least.
One of the best this year
Cheers,
- Pete
Re: Holly Blue: variation in female markings between broods
Posted: Tue Jan 14, 2020 7:30 pm
by David M
millerd wrote: ↑Tue Jan 14, 2020 12:34 pm..Though the general rule remains true that the second has heavier black markings than the first, some of the first nearly approach the second in this respect. What can be seen however, is that the third brood females do not differ particularly from those of the second.
Thanks for this, Dave. Extremely interesting. I presume these findings are borne out on the continent where third brood Holly Blues are commonplace.
As you have found, the main distinction is between the spring brood and the first summer brood.
Perhaps time spent in the pupa plays a role?