Both the Large White (Pieris Brassicae) and and the Small White (Pieris rapae) are common British butterflies, distributed throughout the UK. They are known collectively as the Cabbage White butterfly. Many of them migrate from Europe to the British Isles where they spread throughout, even as far north as the Orkney and Shetlands. The Small White was introduced to Australia in 1939 and is now regarded as a pest there.
Identification of the Large and Small Whites
It is easy to confuse the two common butterflies, although size is obviously a distinguishing feauture. The markings on the edge of the Small White's forewing generally tend to the horizontal while in the Large White, they tend to the vertical. Butterflies which emerge in the summer have darker markings than the earlier brood.
The caterpillars of the Small White are a lighter green in colour compared to those of the Large White which are green and black. Small White caterpillars are generally found singly while those of the Large White cluster together. Large White caterpillars are poisonous to predators so escape their predations despite being so visible on the outer leaves of plants.
Life Cycle of the Cabbage White Butterfly
Both the Large and Small Whites have similar life cycles. Eggs are laid on cruciferous plants (plants with four-petalled flowers) in groups of about forty and after about a week, the caterpillars emerge. They are voracious eaters and can reduce their food plants to mere stalks. The Small White prefers to eat the inner leaves while the Large White tends to remain on the outer leaves.
After around three weeks, the caterpillars become pupae and in a summer brood, this stage lasts a further two weeks before the adult butterfly emerges. For over-wintering, the pupa stage can last around eight months.
In a good year, a third brood can be produced.
Habitat
The Cabbage White butterflies have a choice of over 60 different plants to lay their eggs on and to feed. As well as cabbages, cauliflowers and brussel sprouts and other vegetables of the Brassica family, they will also lay their eggs on nasturtiums and wallflowers. Few plants in the garden seem safe from the ravages of this pest, as many gardeners regard them.
Conservation Status
Not surprisingly, the Cabbage White butterflies (both Large and Small) are not regarded as being endangered although numbers of the Small White have declined slightly. They are among our most common British butterflies and can be seen in most gardens.
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