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Text and photographs protected by Copyright © Adrian Hoskins 2007, and must not be published in part or in whole elsewhere without prior written permission from the author.
Butterflies of Britain & Europe
 
Brimstone
Gonepteryx rhamni LINNAEUS, 1758
Family - PIERIDAE
subfamily - COLIADINAE
 
 introduction | habitats | lifecycle | adult behaviour
 
Brimstone Gonepteryx rhamni, male, Noar Hill, Hampshire, England.
 
Introduction
 
According to popular belief, the word "butterfly" is derived from the expression "butter-coloured fly", a term which may have been applied to the Brimstone. It is one of Britain's most well known and common species; and frequently the first species to be seen when the adults awake from hibernation in early Spring.
 
The Brimstone is a beautiful insect and a grand master of camouflage. The pale greenish underside, raised wing-veins and falcate wing tips combine to disguise the butterfly as a leaf, making it near invisible when at rest under bramble or ivy.
 

Brimstone Gonepteryx rhamni, female at rest, superbly disguised as a leaf, Stockbridge Down.

 
The butterfly is very widespread and common throughout Europe with the exception of Scotland and northern Scandinavia. Beyond Europe it occurs in Morocco, Algeria and across temperate Asia to western Siberia and Mongolia.
 
There are 2 other Gonepteryx species in southern Europe - cleopatra, which is a deeper yellow, and flushed with orange on the forewings of the male; and farinosa, which is almost identical to the Brimstone, it's wings are a slightly different shape, and have a distinct rough texture. The latter species is confined to Turkey, Greece, Bulgaria, Albania and the Middle East.
 
Habitats
 
In Britain the Brimstone is common in the southern half of England and in south Wales, but becomes scarcer further north. In Scotland it occurs only as a vagrant.
 
Whereas most butterflies have very strict habitat requirements and are thus localised in distribution, the Brimstone is highly mobile and can be seen in almost any habitat within it's distribution range. A given insect may wander many miles from it's emergence site, breeding with insects from other areas. This helps it to maintain a high level of genetic diversity, resulting in a hardy species that is highly adaptable, and not prone to major population fluctuations from year to year.
 
The Brimstone is commonest on chalk grassland or deciduous woodland sites, but will breed almost anywhere where the larval foodplants grow, including heathland, moors, farmland, railway cuttings, and coastal habitats. It is also regularly seen in gardens, parks, and even along motorway embankments, "re-fuelling" at roadside flowers, when dispersing in search of new habitats.
 
Brimstone Gonepteryx rhamni, female, Noar Hill, Hampshire, England.
 
Lifecycle
 

The butterflies emerge in late June or early July, and are usually on the wing until late August or early September, when they enter hibernation. During the winter months they sometimes awaken and fly on sunny days, but do not become fully active again until late March or early April.

 

In April and May they lay their pale greenish-white skittle-shaped eggs singly on the buds or young leaves of buckthorn bushes, chiefly alder buckthorn Frangula alnus on acid soils, or purging buckthorn Rhamnus catharticus on chalk or limestone.

 

The butterflies will oviposit on almost any buckthorn, regardless of it's size or situation - I have found eggs on tiny isolated plants in full sunlight on open heathland, on large flourishing bushes on chalk grassland, as well as in woodland, where bushes in semi-shade deep in the understorey are used as often as those in sunlight along ride edges. The eggs can be laid at any height between 0.5 and 3 metres.

 

The eggs are laid singly but I have counted up to 19 on a single leaf, and up to 100 on a single bush, laid over several days during repeat visits by one or more females. Eggs are laid over a protracted period - I have observed Brimstones ovipositing on the buds of tiny buckthorn plants in early April, on developing buds and young leaves in late April, and on the fully developed leaves of tall buckthorn bushes in late May.

 

When small, the larvae feed on the underside of the leaves, usually resting close to the midrib. Older larvae can be easily found resting on the upperside of the leaves, with their bodies arched slightly. Throughout their development they are green, and covered with a sprinkling of short and very fine hairs.
 
Brimstone larvae, like those of all butterflies, are prone to viral diseases, parasitoids, and predation. Birds and wasps are the main predators, but I once found a fully grown larva that was being pinned to a leaf by a trio of 4th instar nymph shield bugs, Troilus luridus, which were tugging at it from various directions as they sucked it's body fluids.
 
When ready to pupate, the larva attaches itself by the tail and a thin silk girdle, either to the midrib on the underside of a buckthorn leaf, or to a narrow stem. It hangs in this position for about 24 hours during which the body gradually arches and stiffens prior to moulting the skin, revealing the newly formed chrysalis.
 
The chrysalis is pale green and is superbly camouflaged, but can be found by diligent searching in June and early July. The wing colours of the developing butterfly can be seen about 3 or 4 days before the adult emerges. Emergence takes place mid-morning, and the wing-drying process takes only about 20 minutes.
 
Photographs depicting the Brimstone's lifecycle can be found on the Lifecycle pages.
 
Brimstone Gonepteryx rhamni, female at roost under a dogwood leaf, Stockbridge Down.
 

Brimstone Gonepteryx rhamni, male at rest, Selborne, Hampshire.

 
Adult behaviour

 

Both sexes emerge simultaneously in late June; or early July if the season is late. In the summer they visit woodland flowers including bramble blossom, marsh thistle and spear thistle. On grassland sites the most highly favoured nectar source is wild basil, but knapweeds, musk thistle, spreading bellflower, St John's wort, small scabious, devil's bit scabious, hawkbit, ragwort, teasel, marjoram and buddleia are also visited.

 

Brimstones enter hibernation in August or early September. Typical hibernation sites include bramble bushes, ivy clumps, and tussocks of pendulous sedge.

 

Brimstone Gonepteryx rhamni, male hibernating under bramble leaf, Stansted Forest.

 

Males normally awaken from hibernation several days before the females, typically in early March, although I saw a female in flight in Stansted Forest on 12th January 2008, a full month before the appearance of the first males. In the spring Brimstones nectar at primroses, bugle, bluebell, blackthorn, common violet, dandelion, cowslip, buttercups, daisies, wood anemone, vetches and sallow catkins.

 

In March 2007 at Crab Wood in Hampshire, I witnessed an example of how Brimstones can detect changes in humidity and air pressure. Shortly before midday, I watched 5 males actively investigating bramble bushes in a sunny glade. Initially I thought they were patrolling in search of females, but it soon became clear that they had detected an imminent change in the weather and were looking for roosting sites. One by one they settled under bramble leaves to roost, and a few minutes later the sunshine had gone, clouds had rolled in, and rain was beginning to fall. An hour later, the sun had re-appeared, but the Brimstones remained at roost.

 

Both sexes remain on the wing until June, sometimes overlapping with the newly emerged generation. They are possibly the longest-lived butterfly species on Earth.

 

In spring I have often seen flies settled on the closed wings of basking Brimstones - possibly mistaking the butterfly for a leaf, or perhaps just taking advantage of the heat reflected from the butterfly's wings.

 

Brimstone Gonepteryx rhamni, with companion

 

Females are probably mated within minutes of their first post-hibernation flight. When a male intercepts a virgin female, they usually fly to settle on a bush, and the male attempts to copulate. He rarely succeeds at the first attempt and is often led by the female on a brief courtship flight, during which the pair may ascend to a height of up to 50 meters, with the male constantly fluttering a few inches below the female. The pair eventually return to copulate beneath a bramble leaf or other low foliage.

 

Brimstone Gonepteryx rhamni, mating pair, late March 2008, Crab Wood, Hampshire.

 

Copulation typically occurs in early-mid April. It is normal for Brimstones to remain paired for several days. On 30th March 2008 I found a copulated pair in Crab Wood. A week later on 5th April they were still in copula amongst the same clump of dog's mercury.

 

I recorded an even longer duration in April 1986 when I found a pair of mating Brimstones under a bramble leaf in a Surrey woodland. I marked the spot, and revisited the site the following day, finding them still copulated. Out of curiosity I returned several times during the next few days, during which the weather remained cool. They remained copulated for an amazing 17 days, finally separating and flying off when warmer weather returned at the end of the month.

 

Brimstone, female raising abdomen to signal rejection to male, Portsdown Hill, Hampshire.

 

If a male intercepts a female that has already mated, the female immediately settles, inverts her wings, and raises her abdomen as a rejection signal ( see photo above ). Males usually persist for several minutes however, and the female often flies a short distance, followed by the male. The process is repeated until the male eventually breaks off the pursuit.

 

Brimstone Gonepteryx rhamni, female roosting under dock leaf, Stockbridge Down.

 

In the late afternoon Brimstones seek roosting sites, typically flying into ivy clumps, or settling beneath leaves of bramble, oak, hazel, dock or pendulous sedge.

 
                                                       
Almost every British and European species of butterfly is declining rapidly in numbers, due in most cases to loss or degradation of habitats.
 
You can help to reverse the decline by supporting conservation organisations which purchase and manage habitats as nature reserves, and which lobby government at local, national and international levels, often very successfully, to bring about changes in farming, forestry and urban development policies.
 
Please contact the conservation organisations for advice on how you can help protect British and European butterflies and their habitats. You may be able to offer practical help e.g. by monitoring butterfly populations or helping to manage nature reserves. Donations to these organisations enable them to employ ecologists and biologists. Even if you are unable to provide such help, merely having your name on the membership list can be a powerful tool for conservation organisations wishing to demonstrate the levels of support they have for their policies.

 

 
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