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Part 1 – The Comma egg and larva

This butterfly has an interesting life-cycle in that it has two forms which exhibit different behaviour. Upon emerging from their winter hibernation in March, the adult butterflies mate and eggs are laid. These give rise to a new generation which appears on the wing at the end of June to the beginning of July. The majority of the offspring have dark undersides and rusty orange upper sides and those individuals that survive the summer go on to hibernate in October without mating. The remainder (approximately 20%) have paler undersides and brighter golden upper sides and are known as the form hutchinsoni. These individuals breed and produce another generation which emerges at the end of August and beginning of September. The parents will die before winter but their dark offspring will go on to hibernate with the dark individuals that hatched in June.
The principal trigger for the development of the hutchinsoni form is the day-length, but warm temperatures can also be a factor. It has been found that the majority of larvae that have completed their development before the summer solstice on 21st June (when the days are lengthening), will become the golden form. This strategy enables the butterfly to fit in another brood if there is a warm early spring which will therefore produce a higher proportion of breeding hutchinsoni adults.

The principal larval host plant is Common Nettle (Urtica dioica), but elm, hop and currant species are also used as well as some willows and occasionally hazel. Nettle plants growing in sheltered sunny positions, as well as dappled shade are preferred. Eggs are laid singly, mainly on the upper surface of a leaf, and usually on the tip or one edge. They are similar in appearance to those of the Red Admiral, although (in my experience) the latter species tends to lay more towards the centre of the leaf.
Eggs can hatch in as little as 5 or 6 days, but it usually takes 2-3 weeks. The emerging larva will immediately make its way to the underside of the leaf, where it begins to feed by chewing holes in the centre, before moving to the leaf edge. It will invariably maintain a curled position either when feeding or at rest. This behaviour is carried through until pupation.
Some authors state that larvae of the first brood have 5 instars while those of the second brood have 4 instars. However, Henwood (1997) shows that this is not so, with both broods going through 5 instars. In both broods the early instars remain largely dark with pale markings and spines. The bright colouration on the body and spines usually starts to develop towards the end of the penultimate instar.
In addition, some late-instar larvae can be quite pale, giving rise to correspondingly pale final instars, but the resultant adults will be of normal appearance.
During all stages of its development the larva is trying to camouflage itself by mimicking a bird dropping. This is partly through colouration but also by adopting various contorted shapes while it sits on the underside of a leaf.
A mature final instar larva will reach a length of approximately 32mm.
The larva is fully grown and ready to pupate after approximately 30 days. It usually remains on the host plant and suspends itself from a stem or the underside of a leaf in the “J” position. Pupation takes place within 24 hours.

Vince

Part 2 – The Comma pupa

The fresh pupa soon darkens, taking on the colours and appearance of a withered leaf, complete with small gleaming drops of dew.
There are many elements to the pupa which contribute to its appearance.
The different pupae exhibited various shades of brown colouration, with some being significantly darker than others. After approximately 20 days each pupa suddenly darkened further, masking the developing colouration of the wings within. However the orange/brown wing colours became more apparent in the few hours before emergence as the pupa pales noticeably and the abdominal segments become distended.
One of the emerging adults had a bleached patch on part of one hind wing, probably as a result of some pathological problem.
The butterfly gets it name from the comma-shaped white mark on the underside of the hind wing. Occasionally an aberrant form (ab. o-album) is encountered where the mark is closed.
This report was produced by rearing 4 individuals from eggs laid on 5th and 17th August 2012. A fresh pupa was also found on 4th September. All were raised under cover, so development rates may have been affected. The pupal stages lasted between 12 and 20 days with emergences taking place between 22nd September and 4th October. All adults were released to their sites of origin or other appropriate locations when weather conditions permitted. Further images of eggs and larvae observed in the 2013 and 2017 seasons have now also been added.
Background Notes

The larvae developed as follows:

9th July 2017 - eggs hatched (1st instar larvae).
15th July 2017 - moulted to 2nd instar.
17th-18th July 2017 - moulted to 3rd instar.
20th-22nd July 2017 - moulted to 4th instar.
25th-27th July 2017 - moulted to 5th instar (then all except one larva were released).
5th August 2017 - remaining larva pupated.
15th August 2017 - adult emerged.


Reading References:

The Butterflies of Britain and Ireland (Thomas and Lewington 2014)
UK Butterflies Website

Vince

Hi Vince,

Inspiring work showing a side of entomology often overlooked ...

Good hunting.

Kind regards. Mark

That's a magnificent piece of work, Vince, with many splendid and inspiring photos.

Mike

Magnificent report. Thanks for sharing.

This is fantastic work Vince and should be published as I'd buy it!

Have a goodun

Wurzel

Vince, this is simply superb stuff! Of all the many fantastic facets of this website I feel that your "early stages series" are easily the most educational and visually stunning pieces to be found. Thankyou for sharing, and I mean that sincerely.

Gibster.

Very many thanks for all your your enthusiastic and encouraging comments guys
Getting usable images of the larvae of this species was particularly challenging, so I was relieved to have completed the job in one season. The rest was relatively easy and mainly involved observing the timings of the development of the first few larvae in order that I would hopefully be ready to capture the critical stages of the ones that followed.
The Comma was a particularly interesting species to study and one which produced a lot of new information from my point of view.

I did say that this was to be the final report of the year, but there is one more project, which involves re-working the Brown Hairstreak report. This will be posted in the next few weeks and will hopefully assist any of you that are thinking of rescuing eggs and rearing this species next year.

Vince

Vince Massimo wrote: I did say that this was to be the final report of the year, but there is one more project which involves re-working the Brown Hairstreak report. This will be posted in the next few weeks and will hopefully assist any of you that are thinking of rescuing eggs and rearing this species next year.

That will be of particular interest, Vince. Thanks in advance.