Butterfly Conservation Yorkshire

Brimstone

Photo by D O'Brien

Brimstone Gonepteryx rhamni (Linnaeus 1758 )

Family: Pieridae, subgroup Coliadinae (The Yellows)

Name Origin ( Etymology): Traditionally called the Butter-coloured Fly and from that came Butter-fly. In Latin Gonepteryx means angled pointed wings, while Rhamni is for Buckthorn.

Identification

Very mobile, hibernating resident. One brood, with butterfly stage lasting up to 12 months (approx Jul/Jul). It is unique in that 1 year old overwintered adults can meet their offspring of the new generation in July. Its a very rugged butterfly and damaged or worn individual are unusual for such long lived insect and usually a bird peck at worst.

Photo by Tim Furness

ID tips

Our only large yellow butterfly and similar in size to a Large White and with same purposeful strong directional flight. It spends little time fluttering unlike the other whites. Only the male is citrus yellow, the female being very pale green but both sexes have a orange spot in the centre of both fore and hind wings which you can glimpse in flight plus you can occasionally glimpse the characteristic points on each wing . However the main diagnostic feature in flight is the female is the palest shade of green while the large white a pale cream. When not in flight they always have there wings shut. Both sexes have a pale green underside with realistic cryptic leaf like veining and even brown spots of leaf damage. The head, antennae and eyes are a rich dark burgundy. Both hind and forewings have a characteristic point, like a leaf tip, and its leaf like deep veining means it can literally disappear in front of your eyes when it lands to rest beneath a leaf.

Habitats: Wetlands and Woodlands

It is a strong, fast flying, far ranging species that can turn up in almost every corner of our county. However they do come together to form colonies often in woodlands where they will overwinter and tend to spread out into the wider countryside during the Spring and return to their woodland home later in the year..

The distribution of this insect roughly mirrors that of buckthorns with its northern limit lies mainly across Yorkshire and Cumbria, and into Northumberland, with the occasional sighting into southern Scotland in more recent years.

The maps from teh NBN atlas illustrate Alder Buckthorn prefers the wetlands of the Humberhead levels. Purging Buckthorn preference for limestone along the Magnesian limestone ridge, the tabular hills on the south side of the North York moors and the Craven Limestones.

Buckthorn is a rare plant but widespread which accounts for the Brimstones gypsy lifestyle. Its favoured foodplant in Yorkshire tends to be Alder Buckthorn which is found in damp, marshy areas or as an under-storey in open woodlands. Sometimes associated with old woodlands where it was grown to produce gunpowder charcoal but also for game bird food and cover. Alder Buckthorn became strategically very important after the invention of the Lee Enfield rifle and buckthorn charcoal production from it was state controlled during both world wars.

Often confused at the bud and young leaf stage with alder which also grows in the same wet habitat. It grows mainly as a shrub, only occasionally reaching as high as 5-7m (15-20ft) and tolerates partial shade. It has also been widely planted as part of new hedgerow in the countryside stewardship scheme and by local authorities, nature reserve, biodiversity projects and wildlife trusts and thankfully increasingly in gardens so we are seeing this species more often.

Purging Buckthorn is thorny and can be used in hedging but can grow into a tree 3-10m (10-30ft) in height. It is found along woodland edges and in scrubby areas and hedgerows in limestone areas.

Buckthorn ID Tips

Common or Purging Buckthorn Alder Buckthorn

Common buckthorn leaves are hairless, have toothed edged and curved veins (left two) and leaves have a pointed tip; while alder buckthorn leaves are glossy have smooth edges and parallel veins and red/brown petioles (right two) Alder buckthorn is also easily confused with young common alder and share the hairy karki coloured shoot tips and also grow in the same habitat. Both species are often confused with Dogwood.

Conservation Gardening Tips

Why every butterfly enthusiast should have a buckthorn plant

If you plant a young alder buckthorn plant in your garden you are nearly guaranteed more regularly visits by adults and the delight of watching the eggs develop into caterpillars from April- Late July and thus perfect for school gardens and households with children.

Alder Buckthorn has other big pluses as a garden plant as they flower all summer and attract large numbers of bees and sometimes you can hear the 'buzz' from a buckthorn bush before you see the bush itself! As well as the flower there is the red/black berries which are great food for birds in the autumn.

An all rounder!

Status Common and becoming more widespread with both abundance and occurance increasing rapidly : A climate change winner!

All time high reached in 2023

Abundance Scale =

This species first appeared in the lowlands of southern half of the county in the warm spell in the first half of teh nineteenth century when temperatures were not dissimilar today but then declined and disappeared after Krakatoa in 1884 . It didn't return to York until the warm spell in 1940's but declined again to a minimum in the 1960's . It was the early 80's when it really got a hold again. It first appeared on our monitored sites down in the south in 1984, just as many other species did at that time. It has only reached the Tees in recent times and the spread continues at pace

Continues to show a fast increase in abundance by an incredible 6 fold in the last 20 years (300% in the last decade) as it continues to spread through the county up 70%. It is a big winner with climate change. It only showed a small dip in the ongoing trend during the cool wet summers between 2007-2012 but teh rate of increase seems to be even faster since 2017 with the recent run of warm years

Nationally abundance has increased by 53%. in the last 20 years.

In Yorkshire is reached an all time high in 2023.

Where and When to find

Good sites in Yorkshire where this species has been regularly seen in a good many woodlands and wetlands including: North Cave Wetlands, Strensall Common, Brockadale , Bishop Wood , and Nosterfield Nature Reserve , Potteric Carr , Thorne Moors and Newtondale

They are more active in the morning when temperatures rise above 12'C and its sunny (but not windy ) throughout late Winter and Spring

The majority of our records represent single sightings of wanderers, whilst clusters indicate breeding areas often wetlands & woodlands. The Brimstone is a butterfly invariably seen one or two at a time. Higher counts of 10 plus do occur in some woodlands. The butterfly has been recorded in every month of the year and increasingly reported earlier (Feb/Mar) and later (Sept/Oct). Emergence of the new generation has moved from starting in early August till now mid-July nearly 3 weeks earlier over the last 40 years

Life Cycle

Adults spread widely so it is not surprising we see them but finding their rare foodplant necessitates constant searching. Bothe sexes are not sexually mature untill emerging from hibernation. After wintering in woodlands males emerge first and hunt for females.

Eggs are placed on leaf buds at the shoot tip and the underside of the youngest developing leaves of foodplant leaves . At first ice blue through green and then later pale creamy yellow bottle-shaped eggs are quite conspicuous and are only laid on Buckthorn species. Females will spend time testing the plant selecting those in fairly good light and healthy and she will return many times over the spring months into summer. This species suffers greatly from predation from the tit family with Blue Tits taking large numbers of eggs , larvae and the pupa. The pupa has a uncanny resemblance to a blue tit complete with beak and eyes makes very accurate bird shaped silhouette. To counter birds the Brimstone female tends to select small plants standing on their own away from larger bushes which might attract searching bird looking for easy and predictable food. Even so most of the eggs laid in March and April get predated but fortunately females keep laying eggs well into June. Eggs hatch in 7- 10 days more quickly as temperatures rise.

Later instar larvae with typical arch posture along the mid vein in order to hide its silhouette from below > NB the pre-pupal stage just below the caterpillar before it splits to reveal the chrysalis

Photo by Nyree Fearnley

At first pale yellow larvae feed on the underside of the youngest leaves but rapidly grow and later instars are darker green larvae and masters of deception. Birds hunt by looking for shadows against the sky from beneath the leaves so the the caterpillar as well as being a remarkable match in colour to the leaf rests along the top midrib of the leaf with its tail towards the base of the leaf. It stands on just it tail clasper and last proleg raised up so its body forms an arch. This means a bird looking for a shadow cant the characteristic silhouette when the body is raised. Plus if searching from above its arched shape makes it equally difficult to discern. They grow rapidly in May and take around a month thro' 5 instars to mature and leave the buckthorn to pupate in low vegetation. Its way to dangerous to stay on the foodplant even if you do look like a blue tit. Small Buckthorn plants can be completely defoliated by July but do manage to recover during the rest of summer but continue to show their gnawed stumps of leaves till autumn.

Adult butterflies emerge after about 2 weeks and can remain active until the end of Sept or later, returning to their woodland home. They can re-emerge to take advantage of good conditions to build up reserves. In very hot years they hibernate quickly to maintain their reserves rarely reappearing as it would to big gamble. In wet years they will continue feeding up and can be seen in good numbers in their woodland homes if nectar is abundant till the end of September.

The species shows a strong preference for purple flowers when nectaring, and its long proboscis is well-adapted to feeding on flowers like Teasel. Brimstones often hibernate under evergreen leaves, especially Holly , Ivy and Brambles. They may 'test' the air on warmer winter days and visit ‘Pussy’ Willow catkins Salix sp or Primroses and early Dandelions

I'm really a Blue tit you know! Note the beak and eye

Photo by Nyree Fearnley

Thanks to Nyree Fernley for her contributions

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