Butterflies of Britain
Family - PIERIDAE
subfamily - PIERINAE
Tribe - PIERINI
Pieris brassicae 2nd brood male,
Lardon Chase, Berkshire ©
Large White, often inaccurately referred to as the Cabbage White, is
found across the whole of Europe including the Mediterranean islands
and the sub-arctic areas of Scandinavia. It also occurs in Morocco,
Algeria, Tunisia, Libya, and across temperate Asia to the Himalaya
mountains. It does not occur naturally beyond these regions, but was
accidentally introduced to Chile.
Female Large Whites have a pair of prominent black spots in the
median area of the forewings, but these are absent in the male. The
spots are visible on the underside forewings of both sexes.
sexes can be confused with the Small White
Pieris rapae but in that species the dark markings are
fainter - greyish rather than black - and the wingspan averages only
48mm as compared to the 63mm male and 70mm female of
widely reared in science laboratories where it is used in research
by geneticists, biochemists and physiologists.
Pieris brassicae Hartslock, Oxon ©
As with many other
Pierines, the Large White is strongly migratory and can appear in
virtually any habitat. In Britain it is commonly seen in coastal
areas during migratory influxes, and often occurs in high numbers on
flowery chalk grassland habitats in mid summer. Occasionally a mass
migration takes place. On 31st July 2009 e.g. I witnessed a
gathering of in excess of 250 migrants at Noar Hill in Hampshire.
This site is an isolated hill with a great profusion of nectar
sources and consequently a major refuelling stop for migrants. At
times I could stand in one spot and see 50 or more within a 10 metre
radius. The insects were very active, often flying in migratory
'strings' of 7 or 8 at a time, pausing now and then to nectar avidly
at marjoram, thistles and knapweed. On 9th August that year I
witnessed an even greater concentration of migrants at Broughton
Down, also in Hampshire. Over 700 Large Whites were present, many of
which remained in the vicinity until the end of the month, e.g. when
I revisited on 24th August in cool overcast weather there were still
between 250-300 basking on herbage within a 50m x 30m patch of
The above numbers may sound impressive, but are nothing in
comparison to the massive swarms which occurred in times past. There
are several fascinating accounts of Large White migrations in
C.B.Williams book 'Insect Migration', including this quote from
A more recent record tells of a
swarm that descended on a small island in the Norfolk Broads:
"In 1508, the 23rd year of Henry the 7th, the 9th of July being
relyke Sonday, there was sene at Calleys ( Calais, France ) an
in-numerable swarme of whit buttarflyes cominge out of the
north-este and flyinge south-eastwards, so thicke as flakes of
snowe, that men beinge a shutynge in St Petars fields without
the towne of Calleys could not see the towne at foure of the
clock in the aftarnone, they flew so highe and so thicke".
Large Whites breed primarily in gardens, allotments and farmland
where they often become a pest on cultivated
Brassica ( cabbage, sprouts etc ). Because of its migratory
lifestyle the butterfly is not restricted to these breeding sites,
and appears commonly in a gamut of habitats including woodland
rides, flowery hillsides, meadows, heaths and parks.
There are usually 2 broods of this species in Britain, emerging in
May and August; and sometimes a third brood emerging in October. The
resident population is supplemented by migrants from Europe, which
often arrive in large numbers during the spring and autumn. Thus it
is possible to see adults of this species at any time from February
deep yellow skittle-shaped eggs are laid in batches of up to 100, on
the underside of leaves of cabbage, sprout, nasturtium, sea kale and
other wild or cultivated Cruciferae. The butterflies have been shown
to be able to detect the presence of existing egg batches laid by
other females, and will not normally lay additional batches on the
same plant. The eggs hatch after about 10 days.
caterpillars feed communally, reducing the leaves to a skeleton of
veins before moving on to adjacent plants. They are a major pest,
causing vast damage to Brassica crops
and cabbages grown in gardens and allotments. They are conspicuously
marked in black and yellow aposematic colours, and sequester mustard
oils from the foodplants, which render them distasteful to avian
predators. The mustard oils contain sulphur compounds, which bestow
the larvae and their droppings with an acrid odour.
About 80 percent of larvae are killed by parasitoid wasps
Apanteles glomeratus, which inject
their eggs into them when they are quite small. The eggs hatch
inside them, and the wasp grubs slowly devour the caterpillar's
flesh. When the grubs are fully grown they eat the caterpillar's
vital organs and kill it. They then break out through its skin
leaving it to die, surrounded by a cluster of up to 80 tiny yellow
fluffy wasp cocoons. The wasps hatch from the cocoons the next
spring, and fly in search of more caterpillars to parasitise.
pupa is formed in a vertical or horizontal position, attached by the
cremaster and silken girdle, usually to walls, fences or tree trunks
some distance away from the foodplant. Sometimes however pupation
takes place on a stem or leaf of the foodplant. The pupa occurs in 2
colour forms. Those formed on stems or foliage are a unicolorous
dull green, while those formed on artificial substrates are a pale
buff hue, mottled with tiny black and yellow spots. Many pupae when
freshly formed and soft, are attacked by the parasitoid wasp
Pteromalus puparum, which completes its
entire lifecycle within the pupa. A single Large White pupa can
produce a dozen or more of these tiny wasps, which are very
beautiful creatures, metallic emerald green in colour.
August 1911 Professor Oliver was visiting a small island of
about 2 acres on Sutton Broad in Norfolk. As he
approached he saw the whole island was covered with fluttering
white butterflies. All of them were caught on the sticky leaves
of the insectivorous plant, sundew. Each small plant had
captured 4 to 7 butterflies. Mostly they were still alive when
Professor Oliver saw them. Several counts gave an average of
about six million butterflies caught in this gigantic trap".
Pieris brassicae, 2nd brood male,
Noar Hill, Hampshire ©
Whites are among the first butterflies to take flight on cool or
overcast days, often appearing an hour or more before other species
awaken. In such weather conditions they spend long periods
reflectance-basking, but take flight as soon as
the clouds thin and there is a hint of warmth.
The adult butterflies are highly
mobile, covering vast distances and exploring all available habitats
in search of their larval foodplants and nectar sources. They have a
powerful undulating flight which is undeterred by obstacles such as
trees, bushes and buildings, over which they commonly fly.
Once they arrive at a flowery site they tend to stay for several
days. In sunny weather they make short but regular flights,
pausing briefly every few seconds to nectar at low growing flowers.
Spring nectar sources include dandelion, bugle and wood spurge,
while the summer brood butterflies favour thistles, knapweeds,
marjoram, buddleia, scabious and hemp agrimony.
When a male encounters a gravid (
previously copulated ) female, she dives instantly into grasses or
herbage, snaps her wings shut, and remains motionless, relying on
her underside camouflage to hide from the male. He is usually able
to find her however by detecting her pheromones and tries quite
aggressively to force himself on her. At first she responds by
swaying slowly from side to side. This is quickly followed by her
partly opening her wings, which prevents the male from making
contact from the side. She then raises her abdomen at a steep angle
( possibly emitting a chemical deterrent at the same time ) to
signal her refusal to mate, and the male then flies off.
I have often found copulated pairs
at rest on low foliage or on robust flowers. In July 2009 I had the
unusual experience of watching the precise moment at which
copulation ended. I had been watching a mated pair for a couple of
minutes, from a distance of several feet away when the pair parted.
The male relaxed his anal claspers to release the female, which then
dropped almost to the ground before flying away. The male remained
in position for a while, then opened his wings to bask before flying
in the opposite direction.
In overcast or hazy conditions the
butterflies often bask on low foliage or amongst grasses, holding
their wings half open to deflect solar energy onto the dark thorax.
The butterflies roost overnight in
bushes or high in trees.