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Butterflies of
Britain & Europe
Small White
Pieris rapae
LINNAEUS, 1758
Family - PIERIDAE
subfamily -
PIERINAE
Tribe - PIERINI
introduction
|
habitats |
lifecycle |
adult behaviour
Text and photographs protected by Copyright © Adrian
Hoskins 2007-2008, and must not be reproduced or published in part
or in whole elsewhere in any form without written permission from
Adrian Hoskins. Breach of copyright will be pursued by litigation.
Website designed, produced and owned by
Adrian Hoskins
Small White
Pieris rapae, 2nd brood female,
Noar Hill, Hampshire, England
Introduction
The
Small White is one of the commonest and most widely distributed species in the
world ( the most widespread of all being the Painted Lady ). It occurs
throughout all of Europe, including the sub-arctic areas of Scandinavia, the
Outer Hebrides, all of the Mediterranean islands, the Azores, and the Canary
Isles.
Beyond Europe it occurs in Morocco, Algeria, Tunisia, the Middle East, and
eastward across temperate Asia to Japan. It was introduced to Quebec in 1860,
and to California in 1866. By 1881 it had spread across the whole of the eastern
United States, and is now a common species throughout all of temperate North
America, where it is known by it's alternative name, the Cabbage White. During
the 20th century it was introduced to many more countries, including Bermuda,
Australia, New Zealand and Iceland.
It
can be confused in flight with the Green-veined White
Pieris napi,
but appears brighter, slightly larger, and has a more powerful and purposeful
flight than that species, usually flying in a constant direction.
In
southern Europe it can be confused with the Southern Small White
P.mannii,
in which the black spots in the median area of the forewings are crescent-shaped
( they are round in rapae
); and with the Mountain Small White
P. ergane,
in which the greyish apical spot is squarish ( concave in
rapae
).
Habitats
This is a strongly
migratory species which can be found in any British habitat with the exception
of the highest mountain peaks. However it is far commoner in the vicinity of
gardens, allotments and farmland where crucifers ( cabbage, sprouts etc ) are
grown.
It
is also common in late summer at flowery grassland sites adjoining cruciferous
crops, and along the south coast, as arriving migrants.
Small White
Pieris rapae, 2nd brood female,
Stockbridge Down, Hampshire, England
Lifecycle
In Britain there are normally 2
generations, emerging in May and August. In exceptionally warm
summers there may be a partial 3rd generation emerging in
October. Migrants can arrive at any time, but tend to peak in
April and July. Thus it is possible to see this species at any
time between early April and November.
The pale yellow, skittle-shaped
eggs are laid singly on the underside of the leaves of cabbages
and
sprouts
Brassica,
garden nasturtiums
Tropaeolum, and less commonly on charlock
Sinapis arvensis
or other
wild crucifers. Often several eggs will be laid on the same
plant, or even under the same leaf, but these are laid by
different females, or by successive visits by a single female.
The dull green and
slightly hairy caterpillars feed diurnally on the leaves of the
foodplants. On cabbages the young larvae bury deep into the
heart of the plants, inflicting serious damage to the young
developing leaves. When older they feed openly, nibbling a mass
of irregularly shaped holes out of the leaves, but leaving the
midrib and tougher veins intact.
The larvae of this species
are considered to be a serious commercial pest of cabbages, but
probably do less damage than the larvae of the Cabbage moth
Mamestra
brassicae.
The chrysalis has several colour
forms, ranging from pale green, to a dirty brownish white, with
dark dots on the abdomen. It is attached by the cremaster and a
silk girdle, either vertically or horizontally to fence-posts,
walls, or the underside of shed roofs, windowsills or other
sturdy materials.
Small White
Pieris rapae, 2nd brood female,
Stockbridge Down, Hampshire, England
Adult behaviour
Early in the day, or in overcast conditions, the butterflies bask with their wings half-open, reflecting solar energy onto the thorax and abdomen, which are covered with dark hair-like scales that assist in rapid heat absorption. In sunny conditions they usually keep their wings shut when resting or nectaring, but copulated pairs usually rest with wings partly open.
Males patrol around cabbages and other crucifers, waiting to intercept females. When the sexes meet, the male flies up and down in front of the female, enticing her to settle, and then settles beside her. He then uses his outspread wings to force the female to lean to one side, and bends his abdomen round to copulate with her. Immediately after joining, the pair fly a short distance to settle on the foliage of a nearby plant. If a male intercepts an unresponsive female, she spreads her wings and raises her abdomen as a rejection signal.
Small White Pieris rapae, 2nd brood female, Martin Down NNR, Hampshire, England
The butterflies often congregate in sheltered gardens to oviposit, or to seek nectar at cultivated flowers, particularly favouring buddleia. In the countryside they often gather to nectar at patches of hemp agrimony, marjoram, thistles, knapweeds, yellow rattle, or valerian.
They roost singly, usually on the upper surface of the leaves of bushes or herbaceous plants, even in rainy weather.
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