Butterflies of Britain
Family - PIERIDAE
subfamily - COLIADINAE
Gonepteryx rhamni, male, Noar Hill,
According to popular myth, the word
'butterfly' may be derived from 'butter-coloured fly', a term which
may have been applied to the Brimstone by early naturalists. It is
one of Britain's most well known and common species; and often the
first species to be seen when the adults awake from hibernation in
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.
Gonepteryx rhamni, female at rest, Stockbridge Down,
Brimstone 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
deeper yellow, and flushed with orange on the forewings of the male;
and farinosa which is almost identical
to rhamni except that its wings are a
slightly different shape and have a distinctive rough texture. The
latter species is found only in Turkey, Greece, Bulgaria, Albania
and the Middle East.
Gonepteryx rhamni male, Bentley Wood,
In Britain the Brimstone is common in the southern half of England
and 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 its distribution range.
A given insect may wander many miles from its 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 scrubby chalk grasslands and deciduous
woodlands but it will breed almost anywhere where its larval
foodplants grow, including heathland, farmland, railway cuttings and
coastal habitats. It is also regularly seen in gardens and parks or
meandering along roadsides when dispersing in search of new
Gonepteryx rhamni, female, Stockbridge
emerge in late June or early July, and fly 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. Both sexes remain on the wing
until June, sometimes overlapping with the newly emerged summer
adults. The Brimstone is the longest-lived species in Europe, with an
adult lifespan of up to 11 months.
In April and May
the female lays her pale greenish-white skittle-shaped eggs singly on
the buds or young leaves of buckthorn bushes, chiefly alder buckthorn
Frangula alnus on acid soils such as the
New Forest heaths and woodlands; or Rhamnus
catharticus on chalk or limestone sites.
Brimstone will oviposit on almost any buckthorn, regardless of its
size or situation - I've found eggs on everything from tiny isolated
saplings on open heathland to tall bushes in thickets on chalk
grassland. In woodland, semi-shaded bushes growing deep in the
understorey seem to be used as often as those in sunlight along ride
edges. The eggs can be laid at any height on the plant.
eggs are laid singly but I have found up to 19 on a single leaf, and
up to 100 on a single small bush, laid over several days during repeat
visits by one or more females. Oviposition takes place over a
protracted period - I have seen Brimstones laying on the buds of tiny
buckthorns in early April, on developing buds and young leaves in May,
and on the leaves of tall bushes in early June.
When small, the larvae feed on the underside of the leaves,
peppering them with tiny holes. Older larvae be found resting along
the midrib on the upper surface of the leaves, with the front half
of their bodies arched. Throughout their development they are green,
and covered with a sprinkling of short fine hairs.
Brimstone larvae, like those of
all butterflies are prone to diseases, parasitoids and predation.
Birds ( especially warblers ) 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 Troilus luridus
shield bugs which were tugging at it from various directions as they
sucked its body fluids.
When ready to pupate, the larva attaches itself by the tail and a
thin silk girdle to the underside of a buckthorn leaf, or sometimes
to a narrow stem away from the foodplant. It hangs in this position
for about 24 hours during which the body gradually arches and
stiffens prior to pupation. 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- 4 days before emergence. Emergence takes place
mid-morning, and the wing-drying process takes about 20 minutes.
Gonepteryx rhamni, female, Bedwyn Brail,
Both sexes emerge
together in late June or early July. In the summer they visit woodland
flowers including bramble, marsh thistle, spear thistle and burdock.
They are also very strongly attracted to teasel, and often 3-4
Brimstones can be found on a single flower head. At grassland sites
the most highly favoured nectar source is wild basil, but knapweed,
small scabious, devil's bit scabious, musk thistle, spreading
bellflower, hawkbit, ragwort, marjoram and buddleia are also visited.
hibernation in August or early September. Most entomological books
quote ivy as the commonest hibernation site, and indeed over the years
I have found several individuals tucked beneath ivy leaves - usually
at a height of about 3 metres where ivy densely covers the trunks of
old oaks. I have more frequently however found them beneath bramble
leaves, usually less than a metre above ground level. I've also
commonly found them in tussocks of pendulous sedge, where they settle
in the angle formed by the drooping leaves.
male hibernating under bramble leaf, Stansted Forest ©
awaken from hibernation several days before the females, on the first
sunny and warm day of Spring. This is typically in March, but on the
morning of 21st February 2009, I counted no less than 19 males in Crab
Wood, Hampshire. All were actively searching for females amongst
brambles and ivy. Unusually, on 12th January 2008, I saw a female in
flight in Stansted Forest - a full month before the appearance of the
In the spring
Brimstones nectar at primrose, bugle, bluebell, common violet,
blackthorn, dandelion, cowslip, buttercups, daisies, wood anemone,
vetches and sallow catkins.
Brimstones are very adept
at detecting changes in temperature, humidity and air pressure. At
Crab Wood in March 2007, shortly after midday I watched 5 males
actively investigating bramble bushes in a sunny glade. At first I
thought they were searching for females, but it soon became clear that
they were all looking for places to shelter, having detected an
imminent change in the weather. One by one they settled under bramble
leaves to roost. Minutes later the sunshine disappeared, clouds had
rolled in, and rain was beginning to fall.
Brimstones often bask on the ground with their wings closed and canted
over to present the maximum area towards the sun. At such times
hoverflies Episyrphus and Muscid flies
Helina will often settle on their wings,
possibly after mistaking the butterfly for a leaf, or perhaps just
taking advantage of the heat reflected from its wings.
Courtship takes place on sunny mornings in early spring, and females
are probably mated within a few minutes of their first
post-hibernation flight, in March or April. If a male intercepts a
female that has already mated, she immediately settles and inverts her
wings, then raises her abdomen as a rejection signal. At this point,
if the female is on the ground, the male will often walk onto her open
wings, in which case the female 'freezes' with her abdomen pointing
vertically upwards to prevent the male from copulating. Males usually
persist for several minutes however, and the female often tries to
escape by flying deep into herbage in an attempt to lose her unwanted
Brimstone, female raising
abdomen to signal rejection to male, Hampshire ©
male intercepts a virgin female, they usually fly a short distance to
settle on a nearby bush. The male then attempts to copulate but rarely
succeeds at the first attempt. The female commonly responds by
escalating rapidly to a height of 10-20 metres, with the male in hot
pursuit. Contact is then usually broken, and the pair return
separately to ground level. Invariably within 2 or 3 minutes they meet
again, and another similar chase takes place. Eventually, if the
female is receptive to the males advances she flies to a nearby leaf,
either in a bush or among low herbage, settling beneath it with her
wings closed. The male is then able to move alongside and copulate. He
then adjusts his position until the pair face opposite directions.
normal for Brimstones to remain paired for several days, presumably
because the metabolic rate is very slow during the cool days of early
spring, when frosts and snow commonly occur : On 30th March 2008 I
found a copulated pair in Crab Wood, Hampshire. A week later on 5th
April they were still in copula beneath the same leaf 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 at Tugley Wood in
Surrey - a place which I then visited on almost a daily basis. 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 before finally separating
and flying off when warmer weather returned at the end of the month.
Gonepteryx rhamni, female roosting under dock leaf, Stockbridge