This widespread and familiar white butterfly is one of the most common butterflies in Europe (4). As the name suggests, adults have whitish upper wings. The forewings have black tips and the undersides of the wings are bright yellow, featuring blackish scales. Males and females are easy to distinguish, as females have two prominent black spots and a blackish streak on the forewing (3). The caterpillar has a green body with black spots and fine hairs. A thin yellowish line extends along the centre of the back and the spiracles are bordered with yellow (2).
The small white is typically a double-brooded species, with two generations each year. The eggs, which hatch after around one week, are laid in April and then again in June. The female deposits them singly on the underside of leaves of the foodplants (2). Cultivated brassicas such as cabbages and nasturtium are preferred, although wild brassicas including wild cabbage, hedge mustard and wild mignonette are also used (4). The caterpillars tend to feed on the hearts of cabbages, not on the outer leaves. They are solitary and are fully grown after one month. They then undergo pupation; the pupa is attached either to the foodplant or to fences and other structures. Adults emerge from the pupae of the first generation after roughly three weeks, but the pupae belonging to the second generation overwinter, with adults emerging the following spring. In years when the weather is particularly clement, a third brood may occasionally be produced (2).
The small white has a wide distribution in Britain, but it becomes scarce in the Scottish Highlands. The distribution of this species seems to have stayed fairly stable, however numbers are thought to have dropped following the introduction of insecticides in the 1950s (4). Elsewhere, this butterfly is found throughout Europe and north-west Africa, reaching Asia as far east as Japan (4).
Found in a range of habitats, where the food plants (such as cabbage, nasturtium and related plants) occur (2). Typical habitats include fields, gardens, and waste land, although they are often found in smaller numbers in woodland edges, hedgerows and other sheltered places (4).
Also known as ‘bivoltine’. Insect life cycle that takes 12 months to be complete, but involves two generations in that time. The first generation adults lay eggs that give rise to those of the second generation. The second generation overwinters either as an egg, larva, pupa or adult.
Stage in an insect’s development when huge changes occur, which reorganise the larval form into the adult form. In butterflies the pupa is also called a chrysalis.
The process of becoming a pupa, the stage of an insect’s development, when huge changes occur that reorganise the larval form into the adult form. In butterflies the pupa is also called a chrysalis.
In insects, spiracles are pores on the body where the tubes forming the respiratory system, known as ‘tracheae’, open.
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