Brimstone (Early Stages)

[Vince Massimo]

The adults of most butterfly species in Britain live for as little as a few days to a couple of weeks. The Brimstone however is generally acknowledged as being the longest lived of all, with some individuals lasting for 11 months. After emerging in early July, the adults feed urgently in preparation for the forthcoming winter hibernation. At this time the males pay little attention to the females and both sexes can be easily be approached. After entering hibernation, usually in a clump of evergreen vegetation such as ivy or holly, but also bramble and privet, they can become active on any sufficiently warm day in winter and so could possibly be seen in every month of the year. In mid to late March they start to appear regularly on the wing. These are mainly males which are now avidly searching for females which have yet to become active.

A female Brimstone is not only very good at finding isolated larval food plants (which are sometimes great distances apart), but she is also a very determined egg layer and can sometimes be seen barging through undergrowth to get to the host plant. Two plant species primarily support the larvae of this butterfly; Common Buckthorn (Rhamnus cathartica) found on calcareous soils and Alder Buckthorn (Frangula alnus) which prefers damper acid soils. Usually a single skittle-shaped egg is laid on a leaf or developing leaf bud, but small groupings may also be found. Sometimes, larger groupings of eggs can also be observed on the buds of favoured bushes which are visited by numerous females.

Part 1 - The Egg and Larva

The egg is white when newly laid, but then turns pale yellow and then orange as it develops. It finally turns pale grey before the larva emerges.

Brimstone ovum (freshly laid) - Woldingham, Surrey 30-April-2012

Brimstone ova (freshly laid) - Crawley, Sussex 24-April-2015

Brimstone ovum (freshly laid) - Woldingham, Surrey 10-April-2011

Brimstone ovum (maturing) - Woldingham, Surrey 19-April-2011

Brimstone ova - Crawley, Sussex 21-May-2019

Brimstone ova nearing emergence - Gatwick, Sussex 22-May-2022

Brimstone ova (three hatched) - Gatwick, Sussex 22-May-2022

Brimstone ovum (hatched) - Crawley, Sussex 28-May-2018

After hatching, the 1st instar larva moves to the nearest fresh leaf and commences feeding by chewing holes in either the upperside or underside. When at rest it will either align itself along the midrib on the upperside of the leaf, or against a rib on the underside, particularly so in periods of poor weather. From the 2nd instar onwards, they are usually found feeding, resting and moulting on the upperside of the leaf. It soon progresses to feeding on the leaf edges and then whole leaves as it develops. After every moult the newly emerged larvae will consume their old larval skin before they recommence feeding on the plant. One has even been observed eating the shed skin of a sibling that has just moulted.

Brimstone larvae (1st instar) hours old - Crawley, Sussex 11-May-2015

Brimstone larva (1st instar) 1 day old - Crawley, Sussex 12-May-2015

Brimstone larvae (1st instar) at rest - Crawley, Sussex 12-May-2015

Brimstone larva (1st instar with feeding damage) - Crawley, Sussex 30-May-2017

Brimstone larva 1st instar (pre-moult) - Crawley, Sussex 1-June-2017

Brimstone larva 2nd instar (post-moult) - Crawley, Sussex 2-June-2017

Brimstone larva 2nd instar (post moult) consuming old larval skin - Crawley, Sussex 1-June-2018

Brimstone larva (2nd instar) - Crawley, Sussex 6-June-2017

Brimstone larva (2nd instar) - Crawley, Sussex 3-June-2017

Brimstone larvae (2nd instar) - Crawley, Sussex 3-June-2017

Brimstone larva 2nd instar (pre-moult) - Crawley, Sussex 4-June-2017

Brimstone larva (2nd instar moulting to 3rd) - Crawley, Sussex 5-June-2017

Brimstone larva 3rd instar (post moult) consuming old larval skin - Crawley, Sussex 5-June-2017

Brimstone larva (3rd instar) - Crawley, Sussex 6-June-2017

Brimstone larva (3rd instar) - Crawley, Sussex 6-June-2017

Brimstone larva 3rd instar (pre-moult) - Crawley, Sussex 8-June-2017

Brimstone larva 4th instar (post moult) - Crawley, Sussex 8-June-2017

Brimstone larva 4th instar (eating shed skin of another larva) - Crawley, Sussex 10-June-2018

Brimstone larva (4th instar) - Crawley, Sussex 10-June-2017

Brimstone larva 4th instar (eating flower bud) - Crawley, Sussex 14-June-2018

Brimstone larvae (4th instar) - Crawley, Sussex 3-June-2015

Brimstone larva 4th instar (pre-moult) - Crawley, Sussex 14-June-2018

Brimstone larva 4th instar (moulting) - Crawley, Sussex 14-June-2018

Brimstone larva 5th instar (emerging from moult) - Crawley, Sussex 14-June-2018

Brimstone larva 5th instar (emerging from moult) - Crawley, Sussex 14-June-2018

Brimstone larva 5th instar (emerging from moult) - Crawley, Sussex 14-June-2018

Brimstone larva 5th instar (emerging from moult) - Crawley, Sussex 14-June-2018

Brimstone larva 5th instar (emerging from moult) - Crawley, Sussex 14-June-2018

Brimstone larva 5th instar (completing moult) - Crawley, Sussex 14-June-2018

Brimstone larva 5th instar (eating moulted skin) - Crawley, Sussex 14-June-2018

Brimstone larva (5th instar) - Crawley, Sussex 13-June-2017

Brimstone larva (5th instar) - Crawley, Sussex 13-June-2017

Brimstone larva (5th instar) - Crawley, Sussex 14-June-2017

Brimstone larva (5th instar) - Caterham, Surrey 7-June-2012

Although well camouflaged, the larvae are quite easy to detect in the wild due to their characteristic feeding damage and of course they get quite large towards the end of their development. At the slightest disturbance they adopt a characteristic posture where they raise the front half of their body slightly, tucking in the front 3 or 4 pairs of legs as they do so. They can also be seen resting in this position.

Brimstone larva (4th instar) - Crawley, Sussex 3-June-2015

Brimstone larva (4th instar) - Crawley, Sussex 11-June-2017

The posture can also be more aggressive.

Brimstone larva (3rd instar) - Crawley, Sussex 7-June-2018

Brimstone larva (5th instar) - Crawley, Sussex 13-June-2017

This is one of the species which produces droplets of a orange-coloured secretion at the tips of some of the short hairs which cover the body. This has also been observed on Orange-tip larvae, but is more noticeable on the Brimstone because it is a much larger beast. The purpose of this fluid has been the subject of some debate.

Brimstone larva 5th instar (head close-up) - Caterham, Surrey 30-May-2012

Brimstone larva 5th instar (body close-up) - Caterham, Surrey 30-May-2012

When fully grown the larva stops feeding and its colour lightens as it prepares to pupate. It may leave the food plant to seek a safe location in vegetation nearer the ground, but some stay on the host plant. It then suspends itself in a horizontal or head-up position by means of a silken pad at one end and a long silken girdle at the mid-line.

Brimstone larva preparing to pupate - Crawley, Sussex 15-June-2015

Brimstone larva (preparing to pupate) - Crawley, Sussex 24-June-2018

Vince

[Vince Massimo]

Part 2 - The Pupa

The pupa is pale green, imitating a rolled-up leaf, and it takes approximately 14 days for the adult to emerge.

Brimstone pupa on Alder Buckthorn - Caterham, Surrey 17-June-2012

Brimstone pupa - Crawley, Sussex 24-June-2015

Brimstone pupa - Crawley, Sussex 1-July-2018

Pupal Development

Brimstone larva suspended for pupation - Crawley, Sussex 17-June-2017

Preparing to pupate - Crawley, Sussex 18-June-2017

Commencing pupation - Crawley, Sussex 18-June-2017

Larva pupating - Crawley, Sussex 18-June-2017

Larva pupating - Crawley, Sussex 18-June-2017

Larva pupating - Crawley, Sussex 18-June-2017

Larva pupating - Crawley, Sussex 18-June-2017

Larva pupating - Crawley, Sussex 18-June-2017

Larva pupating - Crawley, Sussex 18-June-2017

Completing pupation - Crawley, Sussex 18-June-2017

Discarding old larval skin - Crawley, Sussex 18-June-2017

Attaching cremaster - Crawley, Sussex 18-June-2017

Freshly emerged pupa - Crawley, Sussex 18-June-2017

Brimstone pupa (30 minutes old) - Crawley, Sussex 18-June-2017

Brimstone pupa (3 hours old) - Crawley, Sussex 18-June-2017

Brimstone pupa (6 hours old) - Crawley, Sussex 18-June-2017

Brimstone pupa (24 hours old) - Crawley, Sussex 19-June-2017

In the few days leading up to emergence, the wing case areas gradually change to pale or bright yellow while the antennae and wing root areas show red-brown.

Brimstone pupa (46 hours before emergence) - Crawley, Sussex 25-June-2017

Brimstone pupa (22 hours before emergence) - Crawley, Sussex 26-June-2017

Brimstone pupa (9 hours before emergence) - Crawley, Sussex 26-June-2017

Brimstone pupa (3 hours before emergence) - Crawley, Sussex 27-June-2017

Brimstone pupa (20 minutes before emergence) - Crawley, Sussex 27-June-2017

Brimstone emerging - Crawley, Sussex 27-June-2017

Brimstone emerging - Crawley, Sussex 27-June-2017

Brimstone emerging - Crawley, Sussex 27-June-2017

Brimstone emerging - Crawley, Sussex 27-June-2017

Brimstone emerging - Crawley, Sussex 27-June-2017

Brimstone emerging - Crawley, Sussex 27-June-2017

Brimstone emerging - Crawley, Sussex 27-June-2017

Brimstone male (expanding wings) - Crawley, Sussex 27-June-2017

Brimstone male (expanding wings) - Crawley, Sussex 27-June-2017

That was the emergence of a male butterfly. The following images chart the the pupal development of a female.

Brimstone pupa (38 hours before emergence) - Crawley, Sussex 25-June-2015

Brimstone pupa (15 hours before emergence) - Crawley, Sussex 26-June-2015

Brimstone pupa (8 hours before emergence) - Crawley, Sussex 26-June-2015

Brimstone pupa (3 hours before emergence) - Crawley, Sussex 27-June-2015

Brimstone pupa (1 hour before emergence) - Crawley, Sussex 27-June-2015

Brimstone pupa (15 minutes before emergence) - Crawley, Sussex 27-June-2015

Brimstone emerging - Crawley, Sussex 27-June-2015

Brimstone emerging - Crawley, Sussex 27-June-2015

Brimstone emerging - Crawley, Sussex 27-June-2015

Brimstone emerging - Crawley, Sussex 27-June-2015

Brimstone emerging - Crawley, Sussex 27-June-2015

Brimstone emerging - Crawley, Sussex 27-June-2015

Brimstone emerging - Crawley, Sussex 27-June-2015

Brimstone female (expanding wings) - Crawley, Sussex 27-June-2015

Brimstone female (expanding wings) - Crawley, Sussex 27-June-2015

Background Information

This report was originally produced by rearing a small number of larvae in 2011 and 2012. In April 2015 a further opportunity to study the species arose when a female Brimstone was seen to be ovipositing on a potted Alder Buckthorn plant in my garden. More data was collected following the discovery of further eggs laid in the garden in 2017 and 2018. All the resulting butterflies were released into a suitable and safe habitat.

Brimstone female (reared and released) - Caterham, Surrey 26-June-2011

Other Observations

On 24th April 2015 I observed a female Brimstone egglaying on my potted Alder Buckthorn. A total of 9 eggs were found on the plant in small groups, but they did not appear to have all been laid at the same time. The plant remained un-netted in the garden. The first of the eggs hatched on 11th May 2015 and within the following 10 days all 9 larvae were found. From these, 6 larvae pupated. Three stayed on the host plant, but these were all attacked by small parasitic wasps which injected eggs into them. These insects are part of the superfamily of Chalcid wasps, of which there are thousands of species. The adult wasps emerged fully formed through a hole in the underside of the dead pupae, approximately 4 weeks after their eggs were laid.

Brimstone pupa with parasitic wasp - Crawley, Sussex 20-June-2015

Brimstone pupa (parasitised) - Crawley, Sussex 6-July-2015

Brimstone pupa (parasitised) - Crawley, Sussex 8-July-2015

The 3 larvae that chose to leave the plant were collected and placed in a netted cage where they pupated. These all produced healthy adult butterflies which emerged on 27th, 28th and 29th June 2015 respectively.
On 22nd May 2017 twenty one freshly laid eggs were found on my potted Alder Buckthorn plant. Most of these hatched on 29th May and, by 31st May, fourteen first-instar larvae were located. Twelve larvae reached 5th instar and some were collected for further study as they started to leave the plant.

Development dates for the 2017 eggs are as follows:

22nd May 2017 - 21 eggs found
29th-31st May 2017 - Eggs hatched (1st instar)
2nd June 2017 - Larvae moulted (to 2nd instar)
5th June 2017 - Larvae moulted (to 3rd instar)
8th-9th June 2017 - Larvae moulted (to 4th instar)
11th-13th June 2017 - Larvae moulted (to 5th instar)
16th June 2107 -Larvae stopped feeding and started to leave the plant
17th June 2017 - Larvae started to spin-up
18th-19th June 2017 - Larvae pupated
27th-28th June 2017 - Adults emerged from captive pupae
5th-6th July 2017 - Adults emerged from garden pupae.

On 20th May 2018, 21 eggs were laid on the plant and these started hatching on 28th May.
On 16th and 21st May 2019 approximately 30 eggs were laid on the plant, Only two larvae pupated on the plant, while approximately four others emerged from pupae in surrounding vegetation.

Representative Images of Adults:

The upper sides of the adults are not seen at rest but can be displayed during courtship. In many cases this is when the female is rejecting the male.

Brimstone male and female (during courtship) - Addington, Surrey 14-June-2010

Brimstone male - Coulsdon, Surrey 12-Aug-2012

Brimstone female - Coulsdon, Surrey 11-Aug-2012

Brimstone male - Coulsdon, Surrey 25-July-2011

Brimstone male and female - Coulsdon, Surrey 12-Aug-2012

Reading References:

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

Vince

[Vince Massimo]

This report was completely revised in July 2015 and has now had another significant update. This mainly involves the addition of many new images in parts 1 and 2 (all dated 2017), as well as some minor changes to the text.

Vince

[Pete Eeles]

That's brilliant, Vince - I especially like the parasitic wasp-related images, but I'm kind of weird like that!

Cheers,

- Pete

[Padfield]

That Chalcid wasp looks extremely similar to this insect I found sitting on an adult male brimstone in March this year:





If they prey on the pupae, why would it be marking an adult male? Or is this just a coincidence? Perhaps adult and pupal brimstones have the same scent markers and the Chalcid homes in on these.

Guy

[Vince Massimo]

Thanks Pete, I think I have done as much as I can with this species.

Guy - Brimstones seem to attract all sorts of small flying insects to their wings when at rest. I don't know what the attraction is, but, perhaps they are just basking. However, in the case of the parasitic wasp, I cannot rule out the existence of a residual pupal scent.

Vince