Scanning electron micrograph of eggs of the large white butterfly, Pieris brassicae, also known as the cabbage white.The picture shows part of a group of eggs, each about 0.3mm in diameter and 1mm tall, on the underside of a leaf of Pak choi, Brassica campestris. In the centre, a larva (caterpillar, red) is beginning to emerge from the egg. The egg shell is its first meal. Larvae of P. brassicae are a serious pest, causing leaf loss to brassica crops such as cabbages, kale and brussel sprouts, particularly in gardens. The larvae accumulate mustard oils from the leaves as they feed, and this deters many vertebrate predators such as birds, although the parasitic wasp Cotesia glomeratus can kill as many as 20% of the population in some years. P. brassicae is a migratory species and a strong flier, known to cross hundreds of kilometres of open ocean