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Text and photographs protected by Copyright © Adrian Hoskins 2007, and must not be published in part or in whole elsewhere without prior written permission from the author.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
 
Small White
Pieris rapae LINNAEUS, 1758
Family - PIERIDAE
subfamily - PIERINAE
Tribe - PIERINI
 
 introduction | habitats | lifecycle | adult behaviour
 
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.

 
                                                       
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.

 

 
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.
 
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